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Objectives: To establish normal development of rod electroretinograms in preterm infants and to assess the effects of retinopathy of prematurity (ROP)., Study Design: We measured 88 Naka-Rushton functions from 41 preterm infants at maturities from 30 to 72 weeks postmenstrual age (PMA). Outcomes (log sigma, retinal sensitivity and V(max), retinal responsivity) were compared between control (no ROP), untreated ROP, and treated ROP., Results: In control infants, sensitivity increased by 1.5 log units from 30 to 40 weeks PMA and by a further 0.5 log units by 50 weeks PMA but was 0.5 log units less than in similarly-mature, healthy, term-born infants. Average retinal responsivity increased from 23 microV to 90 microV between 30 and 40 weeks PMA and was 35 muV greater at 40 weeks PMA than in similarly-mature term-born infants. At around 36 weeks PMA, (when onset of ROP peaks), infants with untreated ROP had average retinal sensitivity 0.2 log units lower than control infants; sensitivity was reduced further in infants treated for ROP. Retinal responsiveness did not differ between control subjects and untreated infants with ROP but was greatly reduced in infants treated for ROP., Conclusions: Maturation of rod sensitivity appears to be slowed by preterm birth whereas maturation of rod responsivity is accelerated. ROP reduces retinal sensitivity, and treated ROP reduces both sensitivity and responsivity.

The RPE65 gene encodes the isomerase of the retinoid cycle, the enzymatic pathway that underlies mammalian vision. Mutations in RPE65 disrupt the retinoid cycle and cause a congenital human blindness known as Leber congenital amaurosis (LCA). We used adeno-associated virus-2-based RPE65 gene replacement therapy to treat three young adults with RPE65-LCA and measured their vision before and up to 90 days after the intervention. All three patients showed a statistically significant increase in visual sensitivity at 30 days after treatment localized to retinal areas that had received the vector. There were no changes in the effect between 30 and 90 days. Both cone- and rod-photoreceptor-based vision could be demonstrated in treated areas. For cones, there were increases of up to 1.7 log units (i.e., 50 fold); and for rods, there were gains of up to 4.8 log units (i.e., 63,000 fold). To assess what fraction of full vision potential was restored by gene therapy, we related the degree of light sensitivity to the level of remaining photoreceptors within the treatment area. We found that the intervention could overcome nearly all of the loss of light sensitivity resulting from the biochemical blockade. However, this reconstituted retinoid cycle was not completely normal. Resensitization kinetics of the newly treated rods were remarkably slow and required 8 h or more for the attainment of full sensitivity, compared with <1 h in normal eyes. Cone-sensitivity recovery time was rapid. These results demonstrate dramatic, albeit imperfect, recovery of rod- and cone-photoreceptor-based vision after RPE65 gene therapy.

Aim: To describe the detailed phenotypes of a multi-generation family affected by autosomal dominant cone-rod dystrophy (adCRD) and characterised by marked intrafamilial heterogeneity, due to a novel frameshift mutation in the CRX gene., Methods: Six affected and two unaffected family members underwent detailed ophthalmological examination as well as psychophysical and electrophysiological testing. Mutation screening of the CRX gene and segregation analysis were performed in 14 family members from three generations., Results: Clinical examination of six available mutation carriers showed marked phenotypic heterogeneity, presenting with a reduced cone electroretinogram (ERG) and normal rod ERG in one family branch and a negative ERG in the other as the most striking feature. Genetic screening identified a novel mutation in the CRX gene, c.636delC, that independently segregates with the disease in both branches of the family., Conclusion: The authors identified a novel disease causing mutation in the CRX gene associated with adCRD. Furthermore, we show here for the first time the coexistence of a reduced cone and a negative ERG component in different individuals of the same family, all affected by the same mutation.

Purpose: To evaluate a 15-year-old boy with MLIV (mucolipidosis type IV) and clinical abnormalities restricted to the eye who also had achlorhydria with elevated blood gastrin levels., Methods: In addition to a detailed neuro-ophthalmic and electrophysiological assessment, his mutant mucolipin-1 was experimentally expressed in liposomes and its channel properties studied in vitro., Results: The patient was a compound heterzygote for c.920delT and c.1615delG. Detailed neuro-ophthalmic examination including electroretinography showed him to have a typical retinal dystrophy predominantly affecting rod and bipolar cell function. In vitro expression of MCOLN1 in liposomes showed that the c.1615delG mutated channel had significantly reduced conductance compared with wild-type mucolipin-1, whereas the inhibitory effect of low pH and amiloride remained intact., Conclusions: These findings suggest that reduced channel conductance is relatively well tolerated by the brain during development, whereas retinal cells and stomach parietal cells require normal protein function. MLIV should be considered in patients with retinal dystrophy of unknown cause and screened for using blood gastrin levels.

Purpose: To assess the impact of acute retinal pigment epithelium (RPE) loss on photopic and scotopic sensitivity., Methods: A 68-year-old woman who had been followed for drusenoid RPE detachment in age-related macular degeneration presented with an acute spontaneous retinal pigment epithelium tear. Three months later, she was seen for routine follow-up and was examined by manual photopic and scotopic threshold perimetry (a static 0.46-degree-diameter 660 nm stimulus under photopic conditions; then, following 25 min of dark adaptation, a static 0.46-degree-diameter 532 nm stimulus under scotopic conditions). The stimuli were applied over the RPE defect and at reference points of similar eccentricity in the opposite vertical haemifield of the same eye where the RPE remained present., Results: Acute RPE loss was associated with only a marginal reduction of photopic sensitivity (-1.5 dB) but a pronounced loss of scotopic sensitivity (-19.5 dB)., Conclusion: Our observations show that RPE is essential for scotopic but not for photopic retinal function, supporting the theory that cone photopigment regeneration occurs within the human neurosensory retina independently of the RPE.

Purpose: This study tests whether cones in the rhodopsin-mutant transgenic P23H-3 retina are damaged by ambient light and whether subsequent light restriction allows repair of damaged cones., Methods: P23H-3 rats were raised in scotopic cyclic (12 hours of 5 lux, 12 hours of dark) ambient light. At postnatal day 90 to 130, some were transferred to photopic conditions (12 hours of 300 lux, 12 hours of dark) for 1 week and then returned to scotopic conditions for up to 5 weeks. Photoreceptor function was assessed by the dark-adapted flash-evoked electroretinogram, using a two-flash paradigm to isolate the cone response. Outer-segment structure was demonstrated by immunohistochemistry for cone and rod opsins and by electron microscopy., Results: Exposure for 1 week to photopic ambient light reduced the cone b-wave, the rod b-wave, and the rod a-wave by 40% to 60% and caused shortening and disorganization of cone and rod outer segments. Restoration of scotopic conditions for 2 to 5 weeks allowed partial recovery of the cone b-wave and the rod a- and b-waves, and regrowth of outer segments., Conclusions: Modest increases in ambient light cause rapid and significantly reversible loss of cone and rod function in the P23H-3 retina. The reduction and recovery of cone function are associated with shortening and regrowth of outer segments. Because the P23H mutation affects a protein expressed specifically in rods, this study emphasizes the close dependence of cones on rod function. It also demonstrates the capacity of cones and rods to repair their structure and regain function.

Purpose: Cone dystrophy with supernormal rod response (CDSRR) is a retinal disorder characterized by reduced visual acuity, color vision defects, and specific alterations of ERG responses that feature elevated scotopic b-wave amplitudes at high luminance intensities. Mutations in PDE6H and in KCNV2 have been described in CDSRR. A combined clinical and genetic study was conducted in a cohort of patients with CDSRR, to substantiate these prior, Methods: Seventeen patients from 13 families underwent a detailed ophthalmic examination including color vision testing, Goldmann visual fields, fundus photography, Ganzfeld and multifocal ERGs, and optical coherence tomography. The coding sequences and flanking intron/UTR sequences of PDE6C and KCNV2 were screened for mutations by means of DHPLC and direct DNA sequencing of PCR-amplified genomic DNA. results. Whereas no mutations were detected in the PDE6H gene, mutations in KCNV2 were identified in all patients, in either the homozygous or compound heterozygous state. Ten of the 11 identified mutations were novel, including three missense and six truncating mutations and one gross deletion. The mutations concordantly segregate in all available families according a recessive mode of inheritance. The CDSRR phenotype was associated with reduced visual acuity of variable degree and color vision defects. Macular defects ranging from mild pigmentary changes to distinct foveal atrophy were present in nine patients. Progression of the disease was observed in only three of seven patients with follow-up data., Conclusions: The phenotype of cone dystrophy with supernormal rod response is tightly linked with mutations in KCNV2.

Purpose: A cathode-ray-tube (CRT) monitor-based technique was used to isolate clinically significant components of dark adaptation. The utility of the technique in identifying adaptation abnormalities in eyes with age-related maculopathy (ARM) is described., Methods: A CRT dark adaptometer was developed to assess cone and rod recovery after photopigment bleach. The following measures were obtained: cone recovery rate (R(c); in decades per minute) and absolute threshold (Tf(c); log candelas per square meter), rod recovery rate (R(r); decades per minute), and rod-cone transition (rod-cone break [RCB], in minutes). These components were isolated by appropriately selecting stimulus size, stimulus location, pigment bleach, and test duration and by coupling the CRT with judiciously selected neutral-density (ND) filters. The protocol was developed by using 5 young observers and was tested on 27 subjects with ARM in the study eye and 22 age-matched control subjects., Results: The parameters necessary for effective isolation of cone and early phase rod dark adaptation were a 2.6 ND filter (for a standard CRT monitor, 0.08-80 cd . m(-2) luminance output); a 4 degrees foveated, 200-ms, achromatic spot; approximately 30% pigment bleaching; and a 30-minute test duration. These settings returned obvious rod and cone recovery curves in control and ARM eyes that were compatible with conventional test methods and identified 93% of participants with ARM as having delayed dynamics in at least one of the parameters. Cone recovery dynamics were significantly slower in the ARM group when compared with age-matched control subjects (R(c), 0.99 +/- 0.35 vs. 2.63 +/- 0.61 decades . min(-1), P < 0.0001). Three of the 27 eyes with ARM did not achieve RCB during the allowed duration (30 minutes). The remaining eyes with ARM (n = 24) exhibited a significant delay in rod recovery (R(r)(,) ARM, 0.16 +/- 0.03 vs. controls, 0.22 +/- 0.02 decades . min(-1), P < 0.0001) and the average time to RCB (+/-SD) in the ARM group was significantly longer than in the control subjects (19.12 +/- 5.17 minutes vs. 10.40 +/- 2.49 minutes, P < 0.0001)., Conclusions: The CRT dark-adaptation technique described in this article is an effective test for identifying abnormalities in cone and rod recovery. Slowed cone and rod recovery and a delayed RCB were evident in the eyes with ARM. The test method is potentially useful for clinical intervention trials in which ARM progression is monitored.

Critical flicker frequency (CFF) is the lowest frequency for which a flickering light is indistinguishable from a non-flickering light of the same mean luminance. CFF is related to light intensity, with cone photoreceptors capable of achieving higher CFF than rods. A contemporaneous measure of rod and cone function can facilitate characterization of a retinal degeneration. We used sinusoidal flicker ERG to obtain CFF values, over a wide range of light intensities, in RCS dystrophic (RCS-p(+)) and wild type rats. Recordings were made at PN23, PN44, and PN64. The CFF curve in control animals increased in proportion to the log of stimulus intensity, with a gentle slope over the lowest 4 log-unit intensity range. The slope of the CFF curve dramatically increased for higher intensities, indicating a rod-cone break. In the RCS rats the rod driven CFF was significantly lower in amplitude compared to normal rats at the earliest age tested (PN23). By PN64 the rod driven CFF was immeasurable in the RCS rats. The amplitude of the cone driven CFF approached normal values at PN23, but was greatly reduced by PN44. By PN64 the entire CFF function was greatly depressed and there was no longer a discernable rod-cone break. These CFF/ERG data show that RCS rats exhibit significant early degeneration of the rods, followed soon after by degeneration of the cones. Using this approach, rod and cone function can be independently accessed using flicker ERG by testing at a few select intensities.

In NSE-Hu-Bcl-2 transgenic mice, line 71, retina undergoes early postnatal degeneration linked to the prior death of Müller cells. The purpose of this study was to complete the characterization of this retinal dysfunction by using electroretinographic (ERG) recordings in both scotopic and photopic conditions. Here, we showed that both rod and cone systems were profoundly affected in NSE-Hu-Bcl-2 transgenic mice as soon as 15 postnatal days in accordance with histological study performed previously.

Knowledge about the plastic and regenerative capacity of the retina is of key importance for therapeutic approaches to restore vision in patients who suffer from degenerative retinal diseases. In the retinae of mice, mutant for the presynaptic scaffolding protein Bassoon, signal transfer at photoreceptor ribbon synapses is disturbed due to impaired ribbon attachment to the active zone. In a long-term study we observed, with light and electron microscopic immunocytochemistry and electroretinographic recordings, two overlapping events in the Bassoon mutant retina, i.e. loss of photoreceptor synapses in the outer plexiform layer, and structural remodeling and formation of ectopic photoreceptor synapses in the outer nuclear layer, a region usually devoid of synapses. Formation of ectopic synaptic sites starts around the time when photoreceptor synaptogenesis is completed in wild-type mice and progresses throughout life. The result is a dense plexus of ectopic photoreceptor synapses with significantly altered but considerable synaptic transmission. Ectopic synapse formation is led by the sprouting of horizontal cells followed by the extension of rod bipolar cell neurites that fasciculate with and grow along the horizontal cell processes. Although only the rod photoreceptors and their postsynaptic partners show structural and functional remodeling, our study demonstrates the potential of the retina for long-lasting plastic changes.

Purpose: To examine changes in inner retinal function of nob2 mice, expressing a null mutation in Cacna1f encoding the Ca(V)1.4 subunit of voltage-dependent calcium channels. CACNA1F mutations underlie one form of incomplete X-linked congenital stationary night blindness (CSNB2). In addition to a loss of dark-adapted (rod-driven) visual sensitivity, electroretinogram (ERG) b-waves and oscillatory potentials (OPs) are decreased in CSNB2 patients., Methods: ERGs were recorded under dark-and light-adapted conditions from the corneal surface of nob2 mice, WT littermates and nob4 mice. ERG frequency spectra were calculated by fast Fourier transform (FFT). A FFT-based high-pass filter was used to derive OP waveforms., Results: Under dark-adapted conditions, the dominant frequency of the OPs varied between 90 to 120 Hz in WT mice. In WT mice, OP frequency first increased with flash intensity and then decreased at the highest flash levels while overall OP amplitude increased monotonically with increasing flash intensity. In response to low stimulus flashes, reliable OPs were not obtained from nob2 mice. OPs were only seen at stimulus intensities at or above -1.8 log cd s/m(2), where they occurred at a lower frequency range (70-90 Hz) than for WT mice. When flash stimuli were superimposed against a steady rod-desensitizing adapting field, the amplitude and frequency of WT OPs increased with flash intensity above 0.4 log cd s/m(2). In comparison to WT results, cone-mediated OPs obtained from nob2 mice were smaller in amplitude, of lower frequency and had delayed implicit times. We compared the extent to which OPs and the b-wave were reduced in nob2 mice, by normalizing to the results obtained from WT mice. In comparison to the b-wave, the OPs were relatively spared, under both dark- and light-adapted conditions., Conclusions: In nob2 mice, rod- and cone-driven OPs are reduced in amplitude and occur at a lower frequency range. Since Ca(V)1.4 is expressed in both the inner and outer plexiform layers, these changes are likely to reflect reduced transmission from photoreceptors to bipolar cells as well as alterations in inner retinal function. That the OPs were better preserved than b-waves suggests that inner retinal pathways may be reorganized in response to the decreased bipolar cell response in nob2 mice.

The time-course of dark adaptation provides valuable insights into the function and interactions between the rod and cone pathways in the retina. Here we describe a technique that uses the flash electroretinogram (ERG) response to probe the functional integrity of the cone and rod pathways during the dynamic process of dark adaptation in the mouse. Retinal sensitivity was estimated from the stimulus intensity required to maintain a 30 microV criterion b-wave response during a 40 min period of dark adaptation. When tracked in this manner, dark adaptation functions in WT mice depended upon the bleaching effects of initial background adaptation conditions. Altered dark adaptation functions, commensurate with the functional deficit were recorded in pigmented mice that lacked cone function (Gnat2 ( cplf3 )) and in WT mice injected with a toxin, sodium iodate (NaIO(3)), which targets the retinal pigment epithelium and also has downstream effects on photoreceptors. These data demonstrate that this adaptive tracking procedure measures retinal sensitivity and the contributions of the rod and/or cone pathways during dark adaptation in both WT control and mutant mice.

Age-related macular degeneration is the most common form of legal blindness in westernized societies, and polymorphisms in the gene encoding complement factor H (CFH) are associated with susceptibility to age-related macular degeneration in more than half of affected individuals. To investigate the relationship between complement factor H (CFH) and retinal disease, we performed functional and anatomical analysis in 2-year-old CFH-deficient (cfh(-/-)) mice. cfh(-/-) animals exhibited significantly reduced visual acuity and rod response amplitudes on electroretinography compared with age-matched controls. Retinal imaging by confocal scanning laser ophthalmoscopy revealed an increase in autofluorescent subretinal deposits in the cfh(-/-) mice, whereas the fundus and vasculature appeared normal. Examination of tissue sections showed an accumulation of complement C3 in the neural retina of the cfh(-/-) mice, together with a decrease in electron-dense material, thinning of Bruch's membrane, changes in the cellular distribution of retinal pigment epithelial cell organelles, and disorganization of rod photoreceptor outer segments. Collectively, these data show that, in the absence of any specific exogenous challenge to the innate immune system, CFH is critically required for the long-term functional health of the retina.

Objective: To examine impairment in cone- versus rod-mediated dark adaptation in the parafovea of persons with age-related maculopathy (ARM)., Design: Cross-sectional., Participants: Older adults with ARM at various severity levels from early to advanced (n = 83) and in good retinal health (n = 43), as determined by stereo fundus photographs evaluated with the Age-Related Eye Disease Study severity scale., Methods: Dark adaptation, both cone- and rod-mediated components, was measured with a modified Humphrey Field Analyzer using a target located 12 degrees in the inferior visual field on the vertical meridian, after exposure to a 98% bleach. Information was collected on self-reported problems for activities at night or under dim illumination (Low Luminance Questionnaire [LLQ]) and for activities during daytime conditions (modified National Eye Institute Visual Function Questionnaire [NEI VFQ])., Main Outcome Measures: Cone- and rod-mediated parameters of dark adaptation., Results: Compared with older adults in normal retinal health, ARM patients had significant impairments in rod-mediated parameters of dark adaptation (rod-cone break, rod slope, rod sensitivity) (P<0.0001), which were increasingly abnormal as disease severity increased. Cone-mediated parameters (cone time constant and cone sensitivity) were not impaired. Low Luminance Questionnaire scores and NEI VFQ scores decreased with increased ARM severity (P = 0.0004 and P = 0.0005, respectively); the percent decrease in LLQ scores as a function of disease severity was larger in magnitude than the percent decrease in NEI VFQ scores., Conclusions: Disturbances in rod-mediated but not cone-mediated dark adaptation in the parafovea at 12 degrees in the inferior field on the vertical meridian are characteristic of ARM even in its early phases.

Purpose: To test the hypothesis that early rod dysfunction predicts the blood vessel abnormalities that are the clinical hallmark of retinopathy of prematurity (ROP)., Methods: Two rat models of ROP, induced by exposure to alternating 50%/10% oxygen (50/10 model) from postnatal day (P) 0 to P14, or exposure to 75% oxygen (75 model) from P7 to P14, and controls reared in room air were studied. In a longitudinal design, electroretinographic (ERG) records and digital fundus images were obtained at P20 +/- 1, P30 +/- 1, and P60 +/- 1. Rod sensitivity was derived from the ERG a-wave. Integrated curvature for the arterioles was calculated using Retinal Image multi-Scale Analysis (RISA) software., Results: In both ROP models, rod sensitivity was low at P20. Sensitivity improved by P60 in the 50/10 model, but remained low in the 75 model. Integrated curvature was high at P20 in both ROP models, decreased nearly to normal by P30 in the 50/10 model, but remained high in the 75 model, even at P60. At P20, rod sensitivity correlated with integrated vessel curvature. Furthermore, low rod sensitivity at P20 predicted abnormal retinal vasculature--that is, high integrated curvature--at P30 and P60. In contrast, vessel curvature at P20 did not predict sensitivity at P30 or P60., Conclusions: The rods may instigate the vascular abnormalities that are the clinical hallmark of ROP.

Purpose: To identify mutations in KCNV2 in patients with a form of cone dystrophy characterized by a supernormal rod electroretinogram (ERG)., Methods: The 2 exons and flanking intron DNA of KCNV2 from 8 unrelated patients were PCR amplified and sequenced., Results: We found 1 frameshift, 2 nonsense, 1 non-stop, and 6 missense mutations. Every patient had one or two mutations identified. Of the missense mutations, 4 affected residues were in the amino terminal region of the protein, and two in the pore region., Conclusions: KCNV2 mutations account for most if not all cases of cone dystrophy with a supernormal rod ERG.

To elucidate the molecular mechanisms underlying the light-sensitive retinal degeneration caused by the rhodopsin mutation P23H, which causes retinitis pigmentosa (RP) in humans, we expressed Xenopus laevis, bovine, human, and murine forms of P23H rhodopsin in transgenic X. laevis rod photoreceptors. All P23H rhodopsins caused aggressive retinal degeneration associated with low expression levels and retention of P23H rhodopsin in the endoplasmic reticulum (ER), suggesting involvement of protein misfolding and ER stress. However, light sensitivity varied dramatically between these RP models, with complete or partial rescue by dark rearing in the case of bovine and human P23H rhodopsin, and no rescue for X. laevis P23H rhodopsin. Rescue by dark rearing required an intact 11-cis-retinal chromophore binding site within the mutant protein and was associated with truncation of the P23H rhodopsin N terminus. This yielded an abundant nontoxic approximately 27 kDa form that escaped the ER and was transported to the rod outer segment. The truncated protein was produced in the greatest quantities in dark-reared retinas expressing bovine P23H rhodopsin and was not observed with X. laevis P23H rhodopsin. These results are consistent with a mechanism involving enhanced protein folding in the presence of 11-cis-retinal chromophore, with ER exit assisted by proteolytic truncation of the N terminus. This study provides a molecular mechanism for light sensitivity observed in other transgenic models of RP and for phenotypic variation among RP patients.

Previous experiments indicate that congenital human retinal degeneration caused by genetic mutations that change the Ca(2+) sensitivity of retinal guanylyl cyclase (retGC) can result from an increase in concentration of free intracellular cGMP and Ca(2+) in the photoreceptors. To rescue degeneration in transgenic mouse models having either the Y99C or E155G mutations of the retGC modulator guanylyl cyclase-activating protein 1 (GCAP-1), which produce elevated cGMP synthesis in the dark, we used the G90D rhodopsin mutation, which produces constitutive stimulation of cGMP hydrolysis. The effects of the G90D transgene were evaluated by measuring retGC activity biochemically, by recording single rod and electroretinogram (ERG) responses, by intracellular free Ca(2+) measurement, and by retinal morphological analysis. Although the G90D rhodopsin did not alter the abnormal Ca(2+) sensitivity of retGC in the double-mutant animals, the intracellular free cGMP and Ca(2+) concentrations returned close to normal levels, consistent with constitutive activation of the phosphodiesterase PDE6 cascade in darkness. G90D decreased the light sensitivity of rods but spared them from severe retinal degeneration in Y99C and E155G GCAP-1 mice. More than half of the photoreceptors remained alive, appeared morphologically normal, and produced electrical responses, at the time when their siblings lacking the G90D rhodopsin transgene lost the entire retinal outer nuclear layer and no longer responded to illumination. These experiments indicate that mutations that lead to increases in cGMP and Ca(2+) can trigger photoreceptor degeneration but that constitutive activation of the transduction cascade in these animals can greatly enhance cell survival.

Purpose: To describe the genotype-phenotype correlation in a German family with a novel CRX mutation and to perform a comparative analysis of published cases., Design: Retrospective observational case series, systematic review, and comparative analysis of the literature., Participants: Four related patients with progressive retinal degeneration., Methods: Mutation screening by single-strand polymorphism analysis and direct sequencing. Clinical examination included kinetic visual fields (VFs), 2-color threshold perimetry (2CTP), full-field electroretinography, fundus photography, optical coherence tomography, and fundus autofluorescence (FA) recording., Main Outcome Measures: Visual fields, subjective and objective cone- and rod-specific function, fundus aspect, retinal stratification, and FA., Results: A novel heterozygous complex mutation (c.816delCACinsAA) in CRX predicting the substitution of 27 C-terminal amino acids by 44 novel amino acids, thus abolishing the OTX tail, was identified in a 2-generation family finally diagnosed with cone-rod dystrophy (CRD), which was confirmed by 2CTP. Patients presented with variability in progression, nystagmus, and nyctalopia. Most of the patients were hyperopic. Electroretinography recordings showed residual rod and mixed cone-rod responses in 2 of the subjects. Age-dependent VF losses followed funduscopic changes of progressive atrophy of the retinal pigment epithelium and neuroretina in the macula and midperiphery marked by disturbed FA. Optical coherence tomography showed decreased central retinal thickness. Comparative analysis of the 131 published data sets revealed 2 groups: patients with early and late onset., Conclusions: We described a 2-generation family with a novel mutation in CRX. The resulting phenotype is that of CRD with variable age at onset and progression. The phenotype description of previously published cases is conclusive only for CRD.

Aims: To describe the effects of vitamin A deficiency (VAD) on retinal function and the subsequent recovery following treatment in three patients with systemic conditions (two with Crohn disease; one secondary to IgE syndrome)., Methods: Electrophysiological testing (including pattern electroretinogram, PERG; electroretinogram, ERG; visual-evoked potential) established the diagnosis of VAD. Repeat testing was carried out in two patients to monitor the time course of recovery following intramuscular vitamin A injection. The third patient had repeat recordings following 13 months of oral supplementation., Results: All three patients initially displayed a characteristic absence of rod function associated with VAD. In addition, delayed and reduced amplitude cone ERGs, loss of short wavelength cone (S-cone) function and subnormal macular function were observed in two patients. Restoration of rod and generalised cone function was rapid in the two patients who received intramuscular injection, with normalisation of some electrophysiological responses after only 3 days. Normal S-cone amplitudes and cone latencies were reached within 12 days of vitamin A injection. Macular function returned to within normal limits by 12 days postinjection in one patient, but remained mildly subnormal in the second patient. Full recovery was present after 13 months oral supplementation in the third patient., Conclusions: Novel observations regarding dark-adapted cone function, S-cone function, and PERG are presented. The differences between the effects of VAD on rod and cone function, and their rate of recovery, may reflect differences in the visual cycle between the two photoreceptor classes. The importance of rapidly and accurately diagnosing VAD, a treatable condition, is noted.

Purpose: To determine the baseline characteristics, reliability, and dynamic range of the pattern electroretinogram (PERG) as a tool to monitor progressive RGC dysfunction in the DBA/2J mouse model of glaucoma with spontaneously elevated intraocular pressure (IOP)., Methods: PERGs were recorded from 56 undilated eyes of 28 anesthetized (ketamine-xylazine-acepromazine) DBA/2J mice of different ages (2-4 months, n = 44 eyes; 12-14 months, n = 12 eyes) in response to contrast reversal of gratings that maximize PERG amplitude (95% contrast, 1-Hz reversal, 0.05 cyc/deg spatial frequency, 50 degrees x 56 degrees field size). Robust averaging (1800 sweeps) was used to isolate PERG from background noise. Cone-driven ERGs in response to diffuse light flashes superimposed on a rod-adapting background (FERG) were also recorded., Results: PERGs had consistent waveforms and were reproducible across batches of mice and operators. In 2- to 4-month-old mice (prehypertensive stage), the PERG amplitude (mean, 8.15 +/- 0.4 microV [SEM]) was considerably larger than the noise (mean 1.18 +/- 0.1 microV). The test-retest variability (two different sessions 1 week apart) and interocular asymmetry of PERG amplitude was approximately 30%, and that of PERG latency was approximately 17%. In 12- to 14-month-old mice (advanced hypertensive stage) the PERG amplitude (mean, 1.29 +/- 0.12 microV) was close to that of noise. In 12- to 14-month-old mice the FERG was reduced to a lesser extent compared with the PERG., Conclusions: The PERG has an adequate signal-to-noise ratio, reproducibility, and dynamic range to monitor the progression of functional changes in the inner retina in DBA/2J mice.

Retinal degeneration 10 (rd10) mice are a model of autosomal recessive retinitis pigmentosa (RP), identified by Chang et al. in 2002 (Vision Res. 42:517-525). These mice carry a spontaneous mutation of the rod-phosphodiesterase (PDE) gene, leading to a rod degeneration that starts around P18. Later, cones are also lost. Because photoreceptor degeneration does not overlap with retinal development, and light responses can be recorded for about a month after birth, rd10 mice mimic typical human RP more closely than the well-known rd1 mutants. The aim of this study is to provide a comprehensive analysis of the morphology and function of the rd10 mouse retina during the period of maximum photoreceptor degeneration, thus contributing useful data for exploiting this novel model to study RP. We analyzed the morphology and survival of retinal cells in rd10 mice of various ages with quantitative immunocytochemistry and confocal microscopy; we also studied retinal function with the electroretinogram (ERG), recorded between P18 and P30. We found that photoreceptor death (peaking around P25) is accompanied and followed by dendritic retraction in bipolar and horizontal cells, which eventually undergo secondary degeneration. ERG reveals alterations in the physiology of the inner retina as early as P18 (before any obvious morphological change of inner neurons) and yet consistently with a reduced band amplification by bipolar cells. Thus, changes in the rd10 retina are very similar to what was previously found in rd1 mutants. However, an overall slower decay of retinal structure and function predicts that rd10 mice might become excellent models for rescue approaches., ((c) 2006 Wiley-Liss, Inc.)

Purpose: To describe electroretinographic (ERG) findings in a strain of Standard Wire Haired Dachshund (SWHD)-derived dogs at the ages of approximately 5, 8 and 52 weeks selected for inherited early onset cone-rod dystrophy., Methods: Nineteen affected and 13 age-matched control SWHDs were included in the study. All dogs were subjected to standardized bilateral Ganzfeld ERGs and ophthalmoscopic examinations at regular intervals., Results: Photopic cone-derived ERG amplitudes were significantly lower and never reached similar levels as those recorded in control dogs. In affected dogs there was no increase with age in amplitudes recorded using 30.1 and 50.1 Hz flicker stimuli. In contrast, in the control groups the photopic b-wave amplitude recorded at 50.1 Hz increased significantly from age 5 to 8 and from 5 to 52 weeks. In affected animals, scotopic rod-derived amplitudes were significantly lower for most recordings compared to those of control dogs, although they increased significantly from age 5 to 8 weeks in both affected and controls. Both a- and b-wave implicit times were significantly longer in the youngest affected group when compared to the age-matched control group at 0.6 log cd s/m(2) and 5.1 Hz single flash light stimuli. In the control dogs, however, there was a significant shortening in a-wave implicit times from age 5 to 8 weeks, and in a- and b-wave implicit times recorded at 5.1 Hz single flash stimuli from age 5 to 52 weeks., Conclusions: The described retinal degeneration in the SWHD is an early onset cone-rod dystrophy, initially affecting the cone system most severely. Early functional changes are seen in the rod system as well. Inner retina also appears affected already at a young age with findings indicating postsynaptic functional changes already at the earliest time point studied, at age 5 weeks. The present study further indicates that the canine retina reaches maturity later than previously reported, or that there exist major breed differences.

Purpose: The only mutations reported to date in Japanese patients with Oguchi disease, a rare form of stationary night blindness with autosomal recessive transmission, have been in the SAG (arrestin) gene. The objective of this study was to describe the ophthalmic features and a novel mutation in the GRK1 (rhodopsin kinase) gene in 2 Japanese patients with Oguchi disease., Design: Molecular genetic and observational case study., Participants: A consanguineous family including 2 siblings with Oguchi disease (a 35-year-old man and a 31-year-old woman)., Methods: Best-corrected visual acuity (BCVA), fundus examinations, Goldmann perimetry, color vision tests, and full-field electroretinograms (ERGs) were evaluated. Mutation screening of the SAG and GRK1 genes was performed with polymerase chain reaction amplification and direct sequencing., Main Outcome Measures: Mutations in the GRK1 gene, BCVA, color vision, fundus photographs, visual fields, and ERG findings., Results: Molecular analysis revealed a novel homozygous missense mutation (p.P391H) in the GRK1 gene in both patients. Proline 391 is not only within the functionally important catalytic domain, but is also a phylogenetically conserved amino acid residue among GRK1 orthologs and homologs. No mutation was found in the SAG gene. The unaffected parents were heterozygous carriers of the mutation. Both patients had night blindness, 1.5 BCVA for each eye, normal color vision, and typical fundus appearance with golden-yellow discoloration. The visual fields were normal in the male sibling. The ERGs showed no rod B waves, reduced standard combined responses, and markedly reduced single-flash cone and 30-Hz flicker responses in both patients., Conclusions: A novel homozygous GRK1 mutation (p.P391H) was found in 2 Japanese siblings with Oguchi disease. Visual function in the 2 patients has not deteriorated with age, indicating that the disease is stationary. This is the first report of any patient with GRK1-associated Oguchi disease with markedly reduced cone responses.

Purpose: Cats have two types of horizontal cell (HC); one is axon-bearing (B-type), the other is axonless (A-type). We have previously described neurite sprouting from HCs in response to experimental retinal detachment. Here we sought to determine whether one or both types elaborate these outgrowths., Methods: Sections as well as wholemounts of retinas detached for 3, 7 and 28 days together with control retinas were double or triple labeled with antibodies to the calcium binding proteins calretinin and calbindin, to the synaptic vesicle-associated membrane protein 2 (VAMP2), and to the 70 and 200 kDa subunits of the neurofilament protein. Digital immunofluorescence images were collected by both confocal and two-photon microscopy., Results: In control retina, both HC types label with antibodies to calretinin and calbindin D, but only the A-type also intensely labels with the neurofilament protein antibody. After 3, 7 and 28 days of detachment, these staining patterns persist, but there is a moderate upregulation of neurofilament protein in the B-type cell. In the detached retina, HC processes sprout neurites that appear most commonly as a loose array of fine beaded processes rising from the outer plexiform layer (OPL) into the outer nuclear layer (ONL), or, especially at 28 days, as stout unbranching processes that often cross the ONL en route to the subretinal space where some expand and arborize. Both types are strongly calretinin-positive while being somewhat less positive for antibodies to calbindin D and neurofilament protein. Moreover, they all arise from similarly labeled processes in the distal-most domain of the OPL where the narrowly stratified field of axon terminal boutons of the B-type HC normally innervates rod spherules, two to three thousand per cell. Our data indicate that the HC sprouts apparently arise specifically from the axon terminal of the B-type cell since outgrowths were never seen arising from either type of HC perikaryon or from processes identifiable as A-type dendrites., Conclusions: The data described here point to the specific remodeling of the rod-connected axon terminals of the B-type cell through neurite outgrowth. Rods respond to detachment by withdrawing synaptic terminals from the OPL while cones do not. Those HC outgrowths that terminate within the ONL appear to retain their connection with the retracted terminals. Others apparently have lost their presynaptic targets and cross the ONL in association with hypertrophied Müller cell processes.

Over 100 rhodopsin mutation alleles have been associated with autosomal dominant retinitis pigmentosa (ADRP). These mutations appear to cause photoreceptor cell death through diverse molecular mechanisms. We show that K296E, a rhodopsin mutation associated with ADRP, forms a stable complex with arrestin that is toxic to mouse rod photoreceptors. This cell death pathway appears to be conserved from flies to mammals. A genetics approach to eliminate arrestin unmasked the constitutive activity of K296E and caused photoreceptor cell death through a transducin-dependent mechanism that is similar to light damage. Expressing K296E in the arrestin/transducin double knock-out background prevented transducin signaling and led to substantially improved retinal morphology but did not fully prevent cell death caused by K296E. The adverse effect of K296E in the arrestin/transducin knock-out background can be mimicked by constant exposure to low light. Furthermore, we found that arrestin binding causes K296E to mislocalize to the wrong cellular compartment. Accumulation of stable rhodopsin/arrestin complex in the inner segment may be an important mechanism for triggering the cell death pathway in the mammalian photoreceptor cell.

Background: Multiple sclerosis (MS) has been associated with inflammation of the uveal tract, suggesting an immunological link between the uvea and central nervous system (CNS) in this disease. The retina is embryologically derived from the CNS, and it is conceivable that retinal antigens may also be recognized by the immune system in MS. Electroretinographic abnormalities, as well as retinal autoantibodies, have previously been described in MS. We performed this study to further explore the possibility of retinal autoimmunity in MS., Methods: Thirty-four patients with clinically definite MS and thirty-seven healthy controls were recruited. All patients and controls had standard electroretinographic (ERG) testing done, as well as a brightflash ERG protocol to isolate rod photoreceptor function. Patient and control sera were analyzed for the presence of antiretinal antibodies using Western blot techniques., Results: We found statistically significant differences between MS patients and controls in four ERG parameters. In the MS group, implicit times of the rod-cone b-wave response, cone b-wave response, and rod photoreceptor response were increased. The amplitudes of the photopic oscillatory potentials were reduced in the MS group. Patients with the highest titres of retinal autoantibodies had delayed rod-cone b-wave implicit times and diminished photopic oscillatory potential amplitudes., Conclusions: We report ERG evidence of retinal dysfunction in patients with MS. We also report the first use of the brightflash ERG protocol in MS, which demonstrated rod photoreceptor dysfunction. Patients with the highest antiretinal antibody titres had abnormal ERG recordings. Retinal autoimmunity is a possible explanation for these observed ERG abnormalities in MS patients.

Purpose: To examine photoreceptor function in diabetes in detail by evaluating photoreceptor light activation, deactivation of the photoresponse, and recovery of the photoreceptor after bleaching (dark adaptation) in rats made diabetic with streptozotocin (STZ)., Methods: Animals were assigned to treated and control groups. Light activation in rod photoreceptors was established using a paired-flash electroretinogram (ERG) protocol, and the leading edge of the a-wave was modeled with the mechanisms mediating phototransduction. Deactivation of the photoreceptor response was evaluated at three luminous exposures (1.4-2.2 log cd.m/s-2) using a variable interstimulus interval (ISI) paradigm. Dark adaptation was evaluated at 90-second intervals for 30 minutes after approximately 20% pigment bleach. At each time point, a paired-flash signal (1.4 log cd.s/m-2) was used to extract rod responses., Results: Diabetic animals showed decreased amplitudes of the photoreceptor response 12 weeks after diabetes induction. No difference was found in the rate of deactivation of the photoresponse in diabetic rats. Normalized amplitudes showed that diabetic animals had significantly faster dark adaptation (P<0.01) than did controls., Conclusions: Although photoreceptor activation was abnormal, deactivation was unaltered after 12 weeks of diabetes. The faster relative recovery found in diabetes after bleach, in the presence of normal pigment dynamics, may reflect a decrease in outer segment lengths.

The Nougaret form of dominant stationary night blindness is linked to a G38D mutation in the rod transducin-alpha subunit (Talpha). In this study, we have examined the mechanism of Nougaret night blindness using transgenic mice expressing TalphaG38D. The biochemical, electrophysiological, and vision-dependent behavioral analyses of the mouse model revealed a unique phenotype of reduced rod sensitivity, impaired activation, and slowed recovery of the phototransduction cascade. Two key deficiencies in TalphaG38D function, its poor ability to activate PDE6 (cGMP phosphodiesterase) and decreased GTPase activity, are found to be the major mechanisms altering visual signaling in transgenic mice. Despite these defects, rod-mediated sensitivity in heterozygous mice is not decreased to the extent seen in heterozygous Nougaret patients.

The aim of this study was to investigate the effects of an increase in the saturation of blood oxygen (SaO2) and/or serum glucose on photoreceptor sensitivity in normal subjects and in patients with diabetes mellitus. We monitored cone and rod sensitivity by recording dark-adaptation curves to both green and red test stimuli while inhaling either air (20% O2 + 80% N2) or 100% oxygen in 12 normal subjects and 12 diabetic patients with no (10) or mild (2) retinopathy. We also repeated the experiment in 10 of the normal subjects under hyperglycemia (mean serum glucose: 161 mg/dl). Results show that in normal subjects the dark-adapted cone sensitivity is improved by an increase in SaO2 or by hyperglycemia. Final rod sensitivity is unchanged during hyperoxia and during hyperglycemia when measured with a green test spot. However the kinetics of dark adaptation are altered during hyperglycemia, and an increase in final sensitivity is observed when measured with the red test spot. Inhalation of oxygen during hyperglycemia in normal subjects reduces cone sensitivity compared to that found during hyperglycemia alone (Pasteur effect). In diabetic subjects the dark-adapted cone threshold is comparable to that found in normal subjects, and sensitivity also increases with an increase in SaO2. The final rod threshold, however, is impaired compared to that of the control group, and rod sensitivity is improved by increasing the SaO2. The results suggest that the metabolism of rods and cones may differ in normal subjects: in cones, the rate of metabolism can be augmented by increasing the available oxygen or glucose, whereas rods appear more insensitive to increased blood oxygen saturation and hyperglycemia. In diabetic subjects, both cone and rod metabolism can be increased by supplemental oxygen, indicative of an early rod deficit. The study lends weight to the hypothesis that dark-adapted rods in diabetics are hypoxic before the onset of retinopathy.

Vision in the mesopic range is affected by a number of inherited and acquired clinical disorders. We review these conditions and summarize the historical background, describing the clinical characteristics alongside the genetic basis and molecular biological mechanisms giving rise to rod and cone dysfunction relevant to twilight vision. The current diagnostic gold standards for each disease are discussed and curative and symptomatic treatment strategies are summarized.

The purpose of this study was to compare the a-waves of mGluR6-deficient mice (KO) to that of wild-type mice (WT), and to determine whether the light-adapted electroretinogram of the KO mice originate exclusively from cones. Dark-adapted a-waves were recorded under the same conditions from both types of mice. With a 96-cd/m(2) background, the a-wave from both types of mice showed a rapid recovery over a 50-min period. The analysis of the a-waves in KO mice indicated that the recovery was determined mainly by the rod component. The light-adapted b-wave of WT mice showed no corresponding recovery. We conclude that rod contribution must be considered in the analyses of the light-adapted a-waves of KO mice.

We quantified rod- and cone-related electroretinogram (ERG) responses following subretinal injections of the human-derived retinal pigment epithelial (hRPE) cell line ARPE-19 at age P23 to prevent progressive photoreceptor loss in the Royal College of Surgeons (RCS) rat. Culture medium-injected eyes served as sham controls. At P60, in comparison with sham-injected eyes, all recordings from hRPE-injected eyes showed preserved scotopic a- and b-waves, oscillatory potentials, double-flash-derived rod b-waves and photopic cone b-waves, and flicker critical fusion frequencies and amplitudes. Although the actual preservation did not exceed 10% of a-wave and 20% of b-wave amplitude values in non-dystrophic RCS and deteriorated rapidly by P90, rod- and cone-related ERG parameters were still recordable up to P120 unlike the virtually unresponsive sham-injected eyes.

This study examined the impact of aging and age-related maculopathy (ARM) on the inactivation of phototransduction in rod photoreceptors by measuring the recovery of the a-wave using a paired flash electroretinogram technique. Measurements were made on 32 older adults in normal retinal health, 25 with early ARM, 7 with late ARM, and 20 young adults for comparison purposes. ARM presence and severity were defined by the Wisconsin Age-Related Maculopathy Grading System based on grading of fundus photographs. The inactivation of rod phototransduction exhibited an aging-related slowing. Those with early ARM did not exhibit inactivation slowing over and above what would be expected based on normal retinal aging. Persons in the late stages of ARM exhibited dramatic slowing in inactivation kinetics.

The dynamics of interactions between rod and L-cone driven signals were studied psychophysically in two deuteranopic observers. Flicker detection thresholds for different ratios of rod to L-cone modulation were measured at temporal frequencies between 1 and 15 Hz. A model, which assumes that rod and L-cone driven signals are vector added, can describe the threshold data adequately. We found that up to about 8-10 Hz temporal frequency, rod and L-cone signals interact additively, whereas at higher frequencies the interaction is subtractive. Rod and L-cone signal strengths depend similarly on temporal frequency and are maximal between 3 and 5 Hz. The phase difference between rod and L-cone signals increases linearly with temporal frequency, indicating that their responses have a delay difference of about 20 to 30 ms, consistent with involvement of the faster rod pathway. The data would suggest a nearly complete additivity of the rod and cone driven signals when using flashed stimuli. But, literature data showed only partial additivity of the two, suggesting that different postreceptoral mechanisms are involved in the two tasks.

To investigate retinal involvement in chronic Chagas' disease, we performed electroretinography and retinal fluorescein angiography studies in chagasic patients. Our results demonstrated a dissociated electrophysiological response characterized by both an abnormal reduction of the electroretinographic b-wave amplitude and a delayed latency, under the dark-adaptated condition. These alterations are compatible with a selective dysfunction of the rods. Antibodies raised against Trypanosoma cruzi that also interact with beta1-adrenergic receptor blocked light stimulation of cGMP-phosphodiesterase in bovine rod membranes. The specificity from the antibody-rhodopsin interaction was confirmed by Western blot analysis and antigenic competition experiments. Our results suggest an immunomediated rhodopsin blockade. T. cruzi infection probably induces an autoimmune response against rhodopsin in the chronic phase of Chagas' disease through a molecular mimicry mechanism similar to that described previously on cardiac human beta1-adrenergic and M2-cholinergic receptors, all related to the same subfamily of G-protein-coupled receptors.

We report an observational case study which showed that the rod pathway may have a significant effect on the multifocal electroretinogram (mfERG). A 68-year-old lady diagnosed with Vitamin A deficiency underwent standard ERG and mfERG. ERG rod and cone function were analysed and the first order mfERG responses were determined. At presentation, there was no demonstrable rod function on ERG testing and normal cone function. mfERG P1 amplitude responses were normal but mfERG P1 latency responses were significantly delayed. Four weeks after initiating treatment with intramuscular Vitamin A, ERG rod function significantly improved. However, cone amplitude was reduced and the 30 Hz flicker latencies decreased. Furthermore, mfERG P1 latency returned to normal and interestingly mfERG P1 amplitude responses showed a significant reduction. These results alter our understanding of the mfERG response by indicating that there is a possible inhibitory influence on mfERG responses from rod pathway systems.

Purpose: Numerous mutations of rhodopsin lead to rod cell death and ultimately to complete blindness, yet little is known about the alterations in the physiology of the light sensors containing the aberrant protein, the rod photoreceptors., Methods: Suction pipettes were used to record the light responses from single rod photoreceptors isolated from the retinas of transgenic pigs of various ages and at progressive stages of retinal degeneration., Results: We have observed changes in the photoresponse of transgenic porcine rods containing both wild type and mutant rhodospin. Our findings are consistent with the idea that substitutions at position proline 347 of rhodopsin interfere with the inactivation of R*. In addition the level of photoreceptor degeneration is positively correlated with an acceleration and desensitization of the photoresponse to dim flashes., Conclusions: It appears that the phototransduction cascade, even when initiated by wild type rhodopsin molecules is altered in a way that is progressive with the level of retinal degeneration. A model consistent with our observations introduces the idea of a binding site for the carboxy terminus of rhodopsin on rhodopsin kinase.

Purpose: Congenital stationary night blindness (CSNB) is a group of nonprogressive retinal disorders characterized by impaired night vision that occurs in autosomal dominant, autosomal recessive, or X-linked forms. Autosomal recessive (ar)CSNB seems to be very rare. Mice lacking the metabotropic glutamate receptor 6 (Grm6) have a defect in signal transmission from the photoreceptors to ON-bipolar cells. In the current study, the human orthologue (GRM6) was screened as a likely candidate for arCSNB., Methods: arCSNB individuals of five families were screened for mutations in GRM6. Subsequently, they were examined with standard and 15-Hz flicker electroretinography (ERG). These recordings were compared with those of patients with X-linked CSNB1., Results: Affected individuals in three of five families carried either compound heterozygous or homozygous mutations in GRM6. Strikingly, all of them displayed a distinctive abnormality of the rod pathway signals on scotopic 15-Hz flicker ERG., Conclusions: The novel profile identified in this study suggests the existence of more than two rod pathways. The distinctive ERG feature was not observed in patients with X-linked CSNB1 and additional affected individuals with unknown molecular defect. These observations will help to discriminate autosomal recessive from X-linked recessive cases by ERG and molecular genetic analysis.

Purpose: To monitor visual performance in early age-related maculopathy (ARM)., Methods: We measured monocular visual function-high-contrast visual acuity (HC-VA), central visual fields (mean sensitivity, MS), colour vision (desaturated Panel D-15), Pelli-Robson (P-R), and cone- and rod-mediated multifocal electroretinograms (mfERG) in 13 ARM subjects and 13 age-matched control subjects with normal fundi at baseline and after 1 year. All had visual acuity of 6/12 or better. The mfERG data were compared to templates derived from the control group at baseline. We analysed the mfERG results by averaging the central and peripheral fields and the superior and inferior fields (CP and SI methods) and by calculating the local responses., Results: The mean rod-mediated responses were significantly delayed in the ARM group for the CP (P=0.04) and the SI methods (P=0.03) at baseline compared to the control group. This did not change significantly after 1 year, whereas the mean cone-mediated responses were within the normal range at both times. Although the local analysis revealed lower amplitudes for the cone- and rod-mediated responses at baseline this was not found after 1 year and only the local rod-mediated latencies were delayed at both times (P<0.01). HC-VA, desaturated Panel D-15 and P-R were significantly worse in the ARM group (P< or =0.01) at baseline but did not show further significant deterioration. Progressive fundus changes were found in only two subjects (18%)., Conclusion: Although there was significant impairment of retinal function in early ARM at baseline no further deterioration was evident after 1 year.

Purpose: To generate an animal model of retinal degeneration by using AAV-mediated ribozyme knockdown of the gamma-subunit of the rod cGMP phosphodiesterase (PDEgamma) mRNA in the retina of wild-type mice., Methods: Two hammerhead ribozymes, HRz35 and HRz42, were designed to target the PDEgamma gene in wild-type C57BL/6 mice. The efficiency and specificity of the ribozyme cleavage was tested in vitro against three different types of target: short synthetic RNA oligomers, longer targets transcribed from clones, and full-length mRNA from total retinal RNA extracts. After in vitro validation, the ribozymes were cloned and packaged in a recombinant adenoassociated virus (rAAV) containing a proximal 472-bp murine rod opsin promoter (MOPS) to drive ribozyme synthesis. Three-week-old wild-type C57BL/6 mice were injected subretinally with the vectors. For treated versus partner control retinas, responses to light were measured by full-field electroretinography (ERG), and retinal tissues were examined by light microscopy. Messenger RNA and protein levels of PDEgamma gene were monitored by reverse transcription-polymerase chain reaction (RT-PCR) and Western immunoblot assay., Results: The ribozymes had comparable in vitro kinetic properties in multiple turnover kinetic analyses. Ribozyme HRz35 exhibited a K(cat) of 0.48 minute(-1) and a K(m) of 980 nM, and HRz42 showed a K(cat) of 0.17 minute(-1) and a K(m) of 971 nM. Both ribozymes cleaved at accessible sites in the RNA, as they digested long transcripts transcribed from clones and full-length mRNA from total retinal RNA extracts in vitro. At increasing intervals after subretinal injection with either AAV ribozyme, a 30% to 90% reduction in a- and b-wave amplitudes was observed compared with those in contralateral control eyes that were not injected. Retinal tissue analysis showed that loss of the photoreceptor cells and PDEgamma mRNA and protein paralleled the ERG results., Conclusions: Ribozyme-mediated somatic knockdown of wild-type PDEgamma mRNA in vivo can efficiently reduce the target RNA leading to a loss in rod photoreceptors and in rod-mediated ERG amplitudes, thus generating an animal model of retinal degeneration resembling human RP in an essentially normal adult retina. This vector ribozyme technique should be applicable to other genes associated with RP and perhaps also to mRNAs of phototransduction genes not yet associated with RP. Application of this approach may be age and species independent.

Background: Isolated functional methionine synthase deficiency occurs in the cblE and cblG defects of methylcobalamin metabolism and is one of a number of causes of severely elevated plasma homocysteine. Clinical features are predominantly of a neurological nature but also include functional restriction of the visual system manifesting as loss of visual acuity and nystagmus. As yet, the origin and pathogenesis of impaired vision have not been explained., Materials and Methods: We investigated a patient who was proven by complementation analysis in cultured fibroblasts to belong to the cblG complementation group. Ganzfeld electroretinograms (ERG) and flash visual evoked potentials (VEP) were recorded over a period of 4 years., Results: Amplitudes of all International Society for Clinical Electrophysiology of Vision (ISCEV) standard responses were below normal. The greatest reductions were of rod response to 24 microV, of standard combined response (SC) b-wave to 120 microV, of oscillatory potentials (OP) to 5 microV, of cone response b-wave to 35 microV, and of 30 Hz flicker response to 8 microV. Except for SC and cone a-waves at age 2.5 and 3.5 years, as well as cone b-wave at 3.5 years, amplitudes remained at a subnormal level at follow-up examinations. Implicit times were slightly prolonged (SC b-wave 6 ms, OPs 2 ms, cone b-wave 2 ms, 30 Hz flicker 4 ms) or fell within the normal range. Responses of the flash VEP were severely deformed but reproducible., Conclusions: This is the first report of detailed investigations of the visual system in a patient with isolated methionine synthase deficiency. Reduced oscillatory potentials suggest microvascular damage to the retina through homocysteine. Decreased photoreceptor function as well as ganglion cell loss as indicated by pathological flash VEPs may reflect a cytotoxic impact of homocysteine on neurons of the visual pathway.

Purpose: Early ametropia, particularly myopia, is frequent in children with a history of preterm birth and retinopathy of prematurity (ROP). The retina is known to govern eye growth and refractive development. We tested the hypothesis that deficits in retinal function are significantly associated with early ametropia in ROP subjects., Methods: Scotopic electoretinogram (ERG) responses to full field stimuli were studied in 40 ROP subjects aged 8 weeks to 18 years. The ROP was categorized as treated, untreated, or none. Refractive development of each ROP subject was monitored and compared with normal for age. The rod photoresponse parameters were calculated and the postreceptoral responses derived. The ERG parameters in the ROP subjects were compared with normal values for age., Results: Twelve ROP subjects developed early ametropia, 10 myopia, and two hyperopia. In the majority of ROP subjects, receptoral and postreceptoral response parameters were below the normal mean for age. In the 12 children with early ametropia, rod photoreceptor sensitivity was significantly lower than in emmetropic ROP subjects; and in five tested in infancy, deficits in rod photoreceptor sensitivity antedated development of ametropia. The myopic control subjects had no deficits in response parameters., Conclusions: Retinal dysfunction is significantly associated with early ametropia in these ROP subjects. Thus, mechanisms for the development of ametropia in ROP subjects may involve rod and rod-mediated postreceptoral activity.

Purpose: A prior study showed that some patients with fundus albipunctatus (FA) have severely reduced full-field cone ERGs. The purpose of this study was to investigate the frequency of cone dysfunction and to determine the cause of the reduced full-field cone ERGs in patients with FA and whether the rod system is affected in patients with FA., Methods: Sixteen consecutive patients with FA (from 1993 to 2003; eight males, eight females; mean age, 25.4 years) with an RDH5 gene mutation were studied. The amplitudes and implicit times of the standard cone ERGs in the patients with FA were compared to those obtained from normal subjects (n = 55). The a-waves of cone ERGs were also elicited by a bright flash and were fitted to a mathematical model of the a-wave. Rod ERG responses were elicited by dim blue flashes after 3 hours of dark adaptation., Results: The amplitude of the b-wave of the cone ERG in the FA group varied considerably from within the normal limits to markedly decreased. Six of 16 patients with FA had b-wave amplitudes that were smaller than the lowest limit of the control subjects. The degree of cone dysfunction tended to be more severe in older patients. The analysis of the cone a-wave demonstrated that R(m) (maximal response amplitude) in the patients with FA with reduced standard cone ERGs was significantly smaller than that in control subjects. Rod ERGs were also reduced in the patients with FA who had reduced cone ERGs., Conclusions: In patients with FA, 38% had extensive cone dysfunction. The reduced full-field cone ERGs were mainly due to the loss of cone photoreceptors, and the rod system was also affected in some patients.

Purpose: To investigate the cone- and rod-mediated multifocal electroretinograms (mfERG) in early age-related maculopathy (early ARM)., Methods and Subjects: We investigated the cone- and rod-mediated mfERG in 17 eyes of 17 subjects with early ARM and 16 eyes of 16 age-matched control subjects with normal fundi. All subjects had a visual acuity of 6/12 or better. We divided the ARM subjects into two groups based on drusen size and retinal pigment epithelium abnormalities-a less advanced (ARM1) and a more advanced (ARM2) group. The mfERG data were compared to templates derived from the control group. We analysed the mfERG results for the central and peripheral fields (CP method) and the superior and inferior fields (SI method)., Results: While the mean cone results showed no statistically significant difference between the groups, the rods showed significantly delayed responses in the ARM1 group for the CP and the SI methods, but not in the ARM2 group, although there was a trend of longer latencies compared to the control group., Conclusion: Our results show a functional impairment of the rods in early ARM subjects. As there is histopathological evidence showing earlier rod than cone impairment in early ARM, following the rod function with the mfERG might be helpful in diagnosis or for monitoring the progression of early ARM.

Purpose: To determine the psychophysical differences between two types of retinitis pigmentosa (RP) patients with different rod sensitivities., Methods: Thirty-five RP patients with a visual acuity of > or =0.7 or better were classified by cone-rod perimetry into type 1, those with undetectable rod sensitivity, and type 2, those with measurable rod sensitivity. Their symptoms, age at onset of symptoms, cone and rod sensitivity, and full-field electroretinograms (ERGs) were compared., Results: The age when the symptoms of night blindness were first noticed was 13.1 +/- 3.3 years (mean +/- SD) for type 1 and 34.5 +/- 14.4 years for type 2 patients (P = 0.0001). One of nine type 1 patients (11%) and 10 of 26 type 2 patients (38%) did not have any symptoms of night blindness. The average rod sensitivity within the central 10 degrees was 43.7 +/- 12.0 dB for type 2 patients with night blindness, and 54.8 +/- 6.4 dB for type 2 patients without night blindness (P = 0.014). One of nine (11%) type 1 patients and 9 of 23 (39%) type 2 patients had recordable ERGs (P = 0.13)., Conclusions: These findings indicate that the two types of RP patients, distinguished by their rod sensitivity, have different psychophysical characteristics of the visual system. The course of the disease process and the long-term prognosis for these two types of patients are different.

Aims: To characterise the detailed phenotype of "cone dystrophy with supernormal rod ERG" in a case series of 10 patients., Methods: 10 affected patients were examined clinically and underwent colour fundus photography, with nine undergoing detailed electrophysiological testing. Five patients were assessed further with fundus autofluorescence (AF) imaging, automated photopic and dark adapted perimetry, and dark adaptometry. Detailed colour vision assessment was performed in six subjects. Blood samples were taken from four patients for DNA extraction and mutation screening of NR2E3 was undertaken., Results: The onset of symptoms was in the first and second decades of life. Subjects presented with reduced central vision and marked photophobia. All individuals were myopic and colour vision testing revealed severely reduced colour discrimination predominantly along the red-green axes; tritan colour vision was relatively well preserved. Nyctalopia is a later feature of the disorder. Funduscopy and AF imaging revealed a range of macular appearances. There was electrophysiological evidence of marked macular dysfunction, reduced and delayed cone responses, and supernormal and delayed rod responses. Photopic and dark adapted perimetry revealed central scotomata with widespread peripheral sensitivity loss. No disease causing sequence variants in NR2E3 were identified., Conclusions: The largest case series to date has been described of the clinical, psychophysical and electrophysiological characteristics of this unusual cone dystrophy with supernormal rod responses. Electrophysiological data were consistent with a post-phototransduction, but pre-inner nuclear layer, site of dysfunction. While the definitive diagnosis can only be made with electrophysiological testing, several characteristics that may increase suspicion of this diagnosis are presented.

To examine how rod and cone function are differentially affected during retinal degeneration, and after subretinal cell grafting, we obtained light- and dark-adaptation curves by recording threshold multiunit responses from the superior colliculus of anesthetized rats. Unoperated RCS dystrophic and non-dystrophic rats were used and the effects of subretinal grafting in dystrophic rats of cells known to limit photoreceptor degeneration were examined. The adaptation curves showed that rod function was severely compromised in unoperated dystrophic RCS rats at low luminance levels, even as early as 21 days of age and that cone thresholds became gradually elevated over time. While cell transplantation preserved both rod and cone photoreceptors, rod function did not recover, although further deterioration of cone threshold responses was prevented. This raises concern that measures of outer nuclear layer thickness may not in themselves be an accurate measure of visual capabilities and efficacy of a restoration strategy.