Search

To evaluate color vision changes and retinal processing of chromatic and luminance pathways in subjects with Alzheimer disease (AD) and mild cognitive impairment (MCI) compared with a matched control group and whether such changes are associated with impaired brain glucose metabolism and β-amyloid deposition in the brain.We evaluated 13 patients with AD (72.4 ± 7.7 years), 23 patients with MCI (72.5 ± 5.5 years), and 18 controls of comparable age (P = 0.44) using Cambridge color test and the heterochromatic flicker ERG (HF-ERG). The Cambridge color test was performed using the trivector protocol to estimate the protan, deutan and tritan color confusion axes. HF-ERG responses were measured at a frequency of 12 Hz, which ERGs reflect chromatic activity, and at 36 Hz, reflecting luminance pathway. A study subsample was performed using neuropsychological assessments and positron emission tomography.Patients with AD presented higher mean values indicating poorer color discrimination for protan (P = 0.04) and deutan (P = 0.001) axes compared with the controls. Along the tritan axis, both patients with AD and patients with MCI showed decreased color vision (P = 0.001 and P = 0.001) compared with controls. The analyses from the HF-ERG protocol revealed no differences between the groups (P = 0.31 and P = 0.41). Diffuse color vision loss was found in individuals with signs of neurodegeneration (protan P = 0.002, deutan P = 0.003 and tritan P = 0.01), but not in individuals with signs of β-amyloid deposition only (protan P = 0.39, deutan P = 0.48, tritan P = 0.63), regardless of their clinical classification.Here, patients with AD and patients with MCI present acquired color vision deficiency that may be linked with impaired brain metabolism.

Duchenne muscular dystrophy (DMD) is caused by X-linked inherited or de novo DMD gene mutations predominantly affecting males who develop early-onset muscle degeneration, severely affecting their quality of life and leading to reduced life expectancy. DMD patients may also develop proliferative retinopathy, cataract, ERG abnormalities, altered contrast sensitivity, color vision losses, and elevated flash detection thresholds during dark adaptation. Depending on the position of the genetic alteration in the large DMD gene, it is associated with a lack of the full-length dystrophin protein possibly with an additional loss of one or several other dystrophins, which are normally transcribed from internal promoters in retina and crystalline lens. During the last decades, the properties of the dystrophins have been characterized in patients with different genetic alterations and in genetic mouse models of DMD. The complex expression pattern of the dystrophins in photoreceptors, Müller glial cells and astrocytes, likely influences synaptic transmission, ionic balance and vascular integrity of the retina. However, the specific function of each retinal dystrophin remains largely unknown. This review describes the current knowledge on dystrophin expression, the putative molecular, structural, and physiological properties of retinal dystrophins, and the main clinical implications associated with the loss of dystrophins in DMD patients and mouse models. Current data and working hypotheses warrant future research on retinal dystrophins to increase our understanding of dystrophin function in the central nervous system in general and to unveil new retinal mechanisms and therapeutic avenues for retinal diseases.

International audience; The mdx52 mouse model of Duchenne muscular dystrophy (DMD) is lacking exon 52 of the DMD gene that is located in a hotspot mutation region causing cognitive deficits and retinal anomalies in DMD patients. This deletion leads to the loss of the dystrophin proteins, Dp427, Dp260 and Dp140, while Dp71 is preserved. The flash electroretinogram (ERG) in mdx52 mice was previously characterized by delayed dark-adapted b-waves. A detailed description of functional ERG changes and visual performances in mdx52 mice is, however, lacking. Here an extensive full-field ERG repertoire was applied in mdx52 mice and WT littermates to analyze retinal physiology in scotopic, mesopic and photopic conditions in response to flash, sawtooth and/or sinusoidal stimuli. Behavioral contrast sensitivity was assessed using quantitative optomotor response (OMR) to sinusoidally modulated luminance gratings at 100% or 50% contrast. The mdx52 mice exhibited reduced amplitudes and delayed implicit times in dark-adapted ERG flash responses, particularly in their b-wave and oscillatory potentials, and diminished amplitudes of light-adapted flash ERGs. ERG responses to sawtooth stimuli were also diminished and delayed for both mesopic and photopic conditions in mdx52 mice and the first harmonic amplitudes to photopic sine-wave stimuli were smaller at all temporal frequencies. OMR indices were comparable between genotypes at 100% contrast but significantly reduced in mdx52 mice at 50% contrast. The complex ERG alterations and disturbed contrast vision in mdx52 mice include features observed in DMD patients and suggest altered photoreceptor-to-bipolar cell transmission possibly affecting contrast sensitivity. The mdx52 mouse is a relevant model to appraise the roles of retinal dystrophins and for preclinical studies related to DMD.

Purpose Human oscillatory potentials (OPs) are derived from dark-adapted (DA) electroretinograms (ERGs) with fixed frequency cutoff filters while light-adapted (LA) OPs are generally not isolated from ERGs. Our purpose was to analyze the effect of cutoff frequencies on DA and LA ERG components using a series of fixed and variable filters. Methods DA and LA ERGs were recorded from 10 healthy eyes of 10 subjects (mean age = 20.5 ± 6.7 years) following ISCEV standards. Each signal was filtered in the Fourier domain to acquire slow (a- and b-waves; below cutoff frequency) and fast (OPs; above cutoff frequency) components. Fixed cutoff frequencies ranged from 60 to 105 Hz and a variable cutoff frequency was calculated. Results were analyzed with statistical tests and specific models. Results DA ERG components were slightly influenced by the filter cutoff frequency. In contrast, fixed and variable filters significantly changed LA components: the lower the cutoff frequency the smaller the b-wave and OP3 and the higher the OP2/OP4 amplitudes. Analyzing the filter frequency limits a transition range between 68.9 Hz and 83.9 Hz was observed where amplitudes vary. Conclusions The present report shows that DA OPs may be isolated from ERGs using filtering procedures with high-pass cutoff frequency at about 75 Hz as recommended by ISCEV. On the other hand, the spectral distribution of low-frequency and high-frequency LA ERG components may overlap. Accordingly, filtering the signal using different cutoff frequencies is not necessarily separating b-wave and OPs.

International audience; Purpose: To study the potential effect of a gene therapy, designed to rescue the expression of dystrophin Dp71 in the retinas of Dp71-null mice, on retinal physiology.Methods: We recorded electroretinograms (ERGs) in Dp71-null and wild-type littermate mice. In dark-adapted eyes, responses to flashes of several strengths were measured. In addition, flash responses on a 25-candela/square meters background were measured. On- and Off-mediated responses to sawtooth stimuli and responses to photopic sine-wave modulation (3-30 Hz) were also recorded. After establishing the ERG phenotype, the ShH10-GFP adeno-associated virus (AAV), which has been previously shown to target specifically Müller glial cells (MGCs), was delivered intravitreously with or without (sham therapy) the Dp71 coding sequence under control of a CBA promoter. ERG recordings were repeated three months after treatment. Real-time quantitative PCR and Western blotting analyses were performed in order to quantify Dp71 expression in the retinas.Results: Dp71-null mice displayed reduced b-waves in dark- and light-adapted flash ERGs and smaller response amplitudes to photopic rapid-on sawtooth modulation and to sine-wave stimuli. Three months after intravitreal injections of the ShH10-GFP-2A-Dp71 AAV vector, ERG responses were completely recovered in treated eyes of Dp71-null mice. The functional rescue was associated with an overexpression of Dp71 in treated retinas.Conclusions: The present results show successful functional recovery accompanying the reexpression of Dp71. In addition, this experimental model sheds light on MGCs influencing ERG components, since previous reports showed that aquaporin 4 and Kir4.1 channels were mislocated in MGCs of Dp71-null mice, while their distribution could be normalized following intravitreal delivery of the same ShH10-GFP-2A-Dp71 vector.

Biofeedback training has been used to improve fixation stability in subjects with central vision loss, but the psychophysiological mechanisms underlying the functional improvements resulted was not reported. The aim of this study was to investigate the effects of microperimetric biofeedback training on different visual functions and self-reported quality of vision in subjects with age-related macular degeneration. This case-control study included six subjects (72.0 ± 6.1 years of age) diagnosed with age-related macular degeneration (wet or dry) with low vision (best corrected visual acuity ranging from 0.5 to 0.1 in the study eye) and five healthy volunteers (64.2 ± 3.7 years of age). Ophthalmological and functional examinations were obtained from all subjects twice with an approximately 3-month interval. Subjects with central vision loss performed 12 sessions (10 min each) of biofeedback training between the two examinations. Functional evaluation included: microperimetry, spatial luminance contrast sensitivities, color vision thresholds, visual acuity, and reading speed. Visual performance during daily activities was also assessed using a standardized questionnaire. The ratio (2nd/1st examination) of the spatial luminance contrast sensitivity at lower spatial frequencies were much higher for the training subjects compared with the controls. In addition, self-reported quality of vision improved after the training. The significant improvement of the visual function such as spatial luminance contrast sensitivity may explain the better self-reported quality of vision. Possible structural and physiological mechanisms underlying this neuromodulation are discussed.

Mercury vapor is highly toxic to the human body. The present study aimed to investigate the occurrence of neuropsychological dysfunction in former workers of fluorescent lamps factories that were exposed to mercury vapor (years after cessation of exposure), diagnosed with chronic mercurialism, and to investigate the effects of such exposure on the Autonomic Nervous System (ANS) using the non-invasive method of dynamic pupillometry. The exposed group and a control group matched by age and educational level were evaluated by the Beck Depression Inventory and with the computerized neuropsychological battery CANTABeclipse - subtests of working memory (Spatial Span), spatial memory (Spatial Recognition Memory), visual memory (Pattern Recognition Memory) and action planning (Stockings of Cambridge). The ANS was assessed by dynamic pupillometry, which provides information on the operation on both the sympathetic and parasympathetic functions. Depression scores were significantly higher among the former workers when compared with the control group. The exposed group also showed significantly worse performance in most of the cognitive functions assessed. In the dynamic pupillometry test, former workers showed significantly lower response than the control group in the sympathetic response parameter (time of 75% of pupillary recovery at 10cd/m2 luminance). Our study found indications that are suggestive of cognitive deficits and losses in sympathetic autonomic activity among patients occupationally exposed to mercury vapor.

Purpose The purpose of this study was to characterize changes in the full-field flash electroretinogram (ERG) in association with psychophysical dark-adapted visual thresholds in patients with genetically characterized Duchenne muscular dystrophy (DMD) either lacking Dp427 (Up 30) or at least Dp260 in addition to Dp427 (Down 30). Methods Twenty-one patients with DMD and 27 age-similar controls participated in this study. Dark-adapted (0.01, 3.0, and 10 cd.s/m² flashes) and light-adapted (3.0 cd.s/m² flash) ERGs were recorded following International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocols. Visual detection thresholds to 625-nm (cone function) and 527-nm (rod function) light-emitting diode (LED) flashes (2 degree diameter) were measured during a dark adaptation period after a 1-minute exposure to a bleaching light (3000 cd/m²). Initially, 8 minutes of interleaved 625-nm and 527-nm thresholds were measured. After an additional 5 minutes of dark-adaptation, a second set of threshold measurements to 527-nm stimuli was performed during the subsequent 6 minutes. Results Dark-adapted b-wave amplitude was significantly reduced to all strengths of flash and a-wave in response to the strong flash stimulus was delayed (15.6 vs. 14.7 ms, P < 0.05) in patients with Down 30 compared with controls. Dark-adapted cone thresholds did not differ among the groups (−2.0, −1.8, and −1.7 log cd/m² for Down 30, Up 30, and controls, respectively, P = 0.21). In contrast, dark-adapted rod thresholds were elevated (F(2,36) = 8.537, P = 0.001) in patients with Down 30 (mean = −3.2 ± 1.1 log cd/m²) relative to controls (mean = −4.2 ± 0.3 log cd/m²). Dark-adapted b-wave amplitudes were correlated with dark-adapted rod sensitivity in patients with DMD (Spearman Rho = 0.943, P = 0.005). The changes were much smaller or absent in patients with intact Dp260. Conclusions Dp260 is particularly required for normal rod-system function in dark adaptation.

Purpose To study binocular balance by comparing dichoptic and standard monocular contrast sensitivity function (CSF) in stereonormal and stereoanomalous/stereoblind amblyopic subjects. Methods Sixteen amblyopes and 17 controls participated. Using the capability of the passive three-dimensional display, we measured their CSF both monocularly and dichoptically at spatial frequencies 0.5, 1, 2, 4, and 8 cpds using achromatic Gabor patches on a luminance noise background. During monocular stimulation, the untested eye was covered, while for the dichoptic stimulation the untested eye viewed background noise. Dichoptic CSF of both eyes was acquired within one block. Results In patients with central fixation, dichoptic viewing had a large negative impact on the CSF of the amblyopic eye, although it hardly affected that of the dominant eye. In contrast, dichoptic viewing had a small but significant effect on both eyes for controls. In addition, all participants lay along a continuum in terms of how much their two eyes were affected by dichoptic stimulation: by using two predefined contrast sensitivity ratios, namely, amblyopic sensitivity decrement and dichoptic sensitivity decrement, not only did we find a significant correlation between these variables among all participants, but also the two groups were identified with minimum error using a cluster analysis. Conclusions Dichoptic CSF may be considered to measure visual performance in patients with altered binocular vision, because it better reflects the visual capacity of the amblyopic eye than the standard monocular examinations. It may also be a more reliable parameter to assess the efficacy of modern approaches to treat amblyopia.

Purpose To follow the visual acuity development of children exposed to or infected with the Zika virus (ZIKV) during gestation and to relate potential visual acuity deficits to their clinical condition. Methods In this prospective study, visual acuity was measured via Teller Acuity Cards in three groups of children: (1) those with confirmed ZIKV exposure (ZE) through the mother only, (2) those with confirmed infection (ZI), and (3) unaffected controls. Visual acuity was measured 2-4 times in each child during the first 30 months of age. Results The study included 22 children in the ZE group, 11 in the ZI group, and 27 controls. Visual acuity developed normally in both patient groups, including infected patients (ZI) that did not manifest clinical symptoms. In a small subgroup of patients with characteristics consistent with congenital Zika syndrome (CZS), visual acuity was within normative values, with the exception of single child with chorioretinal atrophy. Conclusions In this southeastern Brazil study cohort, visual acuity development seemed to progress normally in infected children without CZS symptoms.

Purpose To evaluate visual acuity and visual acuity development in children from the state of Sao Paulo, Brazil, who were exposed to the Zika virus (ZIKV) gestationally. Methods Children who had been exposed to ZIKV during gestation and age-matched control subjects received visual acuity and funduscopic examination. ZIKV exposure was confirmed by maternal quantitative polymerase chain reaction testing or serology assay. The ZIKV group was divided into two subgroups: Zika - exposed (ZE), with only the mother having confirmed ZIKV-infection, and Zika-infected (ZI), with confirmed infection. Visual acuity development was compared with prior norms and quantified by measuring visual acuity correlation with age. Results A total of 110 children were included: 47 who had been exposed to ZIKV (ZE, 23; ZI, 24) and 63 controls. Abnormal visual acuity was found in 5 of 24 ZI children. Of the 4 children with microcephaly, only 2 had visual acuity loss (only 1 also had abnormal funduscopic findings). There was significant correlation between age and visual acuity in both the control group ( R 2 = 0.8; P R 2 = 0.6; P R 2 = 0.04; P = 0.38). Furthermore, the increment in octaves/month was much lower in the ZI subgroup. Conclusions Our data indicates that visual acuity losses only occur in infants who suffered gestational-infection, not simply exposure. Lack of correlation between age and visual acuity in the ZI subgroup suggests a slowing of visual development even in the absence of microcephaly. This result may have broad implications for the deleterious effects of ZIKV on the central nervous system.

It has been previously demonstrated that electroretinography (ERG) elicited by heterochromatically modulated stimuli can be used for objective determination of color vision type. Color vision of trichromatic, deuteranopic, and protanopic participants was psychophysically assessed by the Cambridge Color Test and confirmed genetically. ERG responses to red and green lights modulating in counterphase at 12 and 36 Hz were recorded, while the fraction of red modulation was varied. At 36 Hz (and second harmonics at 12 Hz), the responses were minimal at red fractions that differed significantly in protanopes. At 12 Hz (fundamental component), the responses of the trichromats differed significantly compared to those of the dichromats. An improved protocol shows that the three subject groups can be separated with no overlap.

Recent research suggested that transcranial direct current stimulation (tDCS) can affect visual processing and that it can be useful in visual rehabilitation. Nevertheless, there are still few investigations on the subject. tDCS selectivity and the extent of its outcomes on visual perception are still to be assessed. Here, we investigate whether central and peripheral visual fields are equally affected by tDCS. We also tried to reproduce a previous work that has evaluated tDCS effects on the central visual field only (Kraft et al. 207:283-290, 2010). Fifteen healthy subjects participated in this randomized repeated-measure design study and received 1.5-mA anodal, cathodal and sham stimulation in different sessions, while performing 10-2 and 60-4 protocols in an automated perimeter. Anodal tDCS significantly decreased thresholds, but was limited to the most eccentric regions of the visual field measured (60°). This suggests that tDCS might be used for rehabilitation of peripheral visual field losses. We did not replicate the excitatory tDCS effect in the central visual field as previously reported by another group. Instead, we observed a trend toward an inhibitory (yet not statistically significant) effect of anodal tDCS on the central field. This might be explained by methodological differences. These results highlight that although tDCS is a technique with a low focality in the spatial domain, its effects might be highly focal in a functional domain. When taken together with previous findings, this also suggests that tDCS may have a differential effect on different retinotopic areas in the brain.

L and M cones send their signals to the cortex using two chromatic (parvocellular and blue-yellow koniocellular) and one luminance (magnocellular) pathways. These pathways contain ON and OFF subpathways that respond to excitation increments and decrements respectively. Here, we report on visually evoked potentials (VEP) recordings that reflect L- and M-cone driven increment (LI and MI) and decrement (LD and MD) activity. VEP recordings were performed on 12 trichromats and four dichromats (two protanopes and two deuteranopes). We found that the responses to LI strongly resembled those to MD, and that LD and MI responses were very similar. Moreover, the lack of a photoreceptor type (L or M) in the dichromats led to a dominance of the ON pathway of the remaining photoreceptor type. These results provide electrophysiological evidence that antagonistic L/M signal processing, already present in the retina and the lateral geniculate nucleus (LGN), is also observed at the visual cortex. These data are in agreement with results from human psychophysics where MI stimuli lead to a perceived brightness decrease whereas LI stimuli resulted in perceived brightness increases. VEP recording is a noninvasive tool that can be easily and painlessly applied. We propose that the technique may provide information in the diagnosis of color vision deficiencies.

Purpose: To determine and compare the intersession test-retest variability of different microperimetric parameters in healthy volunteers and age-related macular degeneration (AMD) patients by MAIA microperimetry. Methods: Twenty-four eyes of 12 healthy volunteers and 22 eyes of 11 AMD patients were included in this study. Microperimetry examinations were performed three times on each eye of all participants by MAIA microperimetry (CenterVue, Padova, Italy). The second measurement was performed on the same day and the third measurement one week after the first test. Retinal light sensitivity, stability of fixation, and macular integrity were recorded. Statistical analysis was performed by Microsoft Excel software and StatSoft Statistica software. Results: During the examinations, the average threshold had not changed significantly (p>0.475) in time in healthy and AMD patients. Fixation stability was relatively constant (nearly 100%) in healthy subjects as compared to the increase in the improving eye condition of AMD patients (p=0.042). Macular integrity was stable in both groups during the examinations. Conclusion: A learning effect was found in fixation stability of AMD patients by MAIA microperimetry. The improvement in fixation stability might be considered, especially prior to biofeedback training protocols in AMD patients.

Electroretinographic measurement instruments allow the variation of several stimulation parameters enabling to study a wide range of retinal processes. The purpose of the present study was to measure human flicker electroretinograms (ERGs) varying temporal modulation, temporal frequency and mean luminance in the photopic and higher mesopic ranges where the change from cone to rod dominance occurs.Fourteen healthy subjects (mean age = 31 ± 6) participated in this study. ERG recordings were performed with the RetiPort system (Roland Consult, Germany). The stimuli were ON and OFF sawtooth waves, square wave and sine wave. The temporal frequencies were 4 and 8 Hz. The mean luminance varied from 1 to 60 cd/m(2).The results confirmed the possibility to distinguish between rod- and cone-dominated retinal responses when using the flicker ERG at different temporal frequencies and luminances. We have also evaluated the responses at luminance levels at which the transition between rod- and cone-dominated responses occurs. This transition between rod- and cone-dominated flicker ERG responses is indicated by a significant change in the response characteristics between 4 and 8 cd/m(2) (between 200 and 400 phot Td).The findings on the transition between rod- and cone-dominated ERGs along with the demonstration of ERG responses to different temporal flicker modulations might be informative for the electrophysiologists when setting up the stimulus at mesopic and photopic luminance levels.

PURPOSE: The present study aimed to compare the postoperative contrast sensitivity functions between wavefront-guided LASIK eyes and their contralateral wavefront-guided PRK eyes. METHODS: The participants were 11 healthy subjects (mean age=32.4 ± 6.2 years) who had myopic astigmatism. The spatial contrast sensitivity functions were measured before and three times after the surgery. Psycho and a Cambridge graphic board (VSG 2/4) were used to measure luminance, red-green, and blue-yellow spatial contrast sensitivity functions (from 0.85 to 13.1 cycles/degree). Longitudinal analysis and comparison between surgeries were performed. RESULTS: There was no significant contrast sensitivity change during the one-year follow-up measurements neither for LASIK nor for PRK eyes. The comparison between procedures showed no differences at 12 months postoperative. CONCLUSIONS: The present data showed similar contrast sensitivities during one-year follow-up of wave-front guided refractive surgeries. Moreover, one year postoperative data showed no differences in the effects of either wavefront-guided LASIK or wavefront-guided PRK on the luminance and chromatic spatial contrast sensitivity functions. OBJETIVO: A proposta do presente estudo é comparar funções de sensibilidade ao contraste obtidas após wavefront-LASIK e wavefront-PRK no olho contralateral. MÉTODOS: Os participantes foram 11 sujeitos saudáveis (idade média=32,4 ± 6,2 anos) com astigmatismo miópico. As funções de sensibilidade ao contraste espacial foram obtidas antes e três vezes após a cirurgia. O programa Psycho e uma placa gráfica da Cambridge Research Systems (VSG 2/4) permitiram gerar os estímulos com contraste espacial de luminância e cromático (verde-vermelho e azul-amarelo) de 0,85 até 13,1 ciclos/grau. Análises longitudinais e comparações entre as cirurgias foram realizadas. RESULTADOS: Não houve mudança significativa da sensibilidade ao contraste durante o primeiro ano após a cirurgia para o olho que recebeu o LASIK ou para o olho que recebeu o PRK. A comparação entre as cirurgias também foi semelhante no pós-operatório de um ano. CONCLUSÕES: Os resultados apresentados mostraram sensibilidade ao contraste semelhante durante o primeiro ano após a cirurgia refrativa com o wavefront. Além disso, no pós-operatório de um ano não houve diferença nas funções de sensibilidade ao contraste de luminância e cromático entre os olhos que receberam LASIK e os que receberam PRK.

Purpose The dystrophin mouse mutant mdx3Cv exhibits scotopic electroretinograpic (ERG) abnormalities, which resemble clinical changes observed in Duchenne muscular dystrophy (DMD) patients. In the present study, ERGs obtained from mdx3Cv and their wild-type littermates under scotopic, mesopic, and photopic conditions were analyzed to provide further insight on the affected retinal pathways, and to compare them with human data. Methods Electroretinograms of mdx3Cv (n = 9) and age-matched C57BL/6J mice (n = 10) included the scotopic full-field flash (for outer retinal deficits in rod pathway), scotopic threshold response (for inner retinal integrity), photopic flash, sinusoidal flicker (for outer retinal deficits in cone pathway), mesopic rapid-on/-off sawtooth flicker, and photopic long-duration flash measurements (for separate ON-/OFF-responses under different conditions). Results The mdx3Cv mice exhibited diminished and delayed scotopic and photopic ERGs, particularly in their b-wave and oscillatory potentials. Interestingly, homologues to the a- and b-wave of the mesopic ON-response were affected in their peak/trough times but not in their amplitude, whereas changes to both features were uncovered for photopic ON-response and sinusoidal flicker. Mesopic and photopic OFF-components were within the norm. Conclusions Abnormal scotopic and photopic flash ERGs were observed in mdx3Cv, which corroborate with deficits that are likely restricted to the level of photoreceptor-to-bipolar cell transmission. Further overlaps between mdx3Cv mice and DMD patients exist, including asymmetrical ON versus OFF ERG alterations under mesopic versus photopic vision. In mice, ON-pathway function is compromised, whereas the OFF-pathway is spared.

In congenital color blindness the red–green discrimination is impaired resulting in an increased confusion between those colors with yellow. Our post-receptoral physiological mechanisms are organized in two pathways for color perception, a red–green (protanopic and deuteranopic) and a blue–yellow (tritanopic). We argue that the discrimination losses in the yellow area in congenital color vision deficiency subjects could generate a subtle loss of discriminability in the tritanopic channel considering discrepancies with yellow perception. We measured color discrimination thresholds for blue and yellow of tritanopic channel in congenital color deficiency subjects. Chromaticity thresholds were measured around a white background (0.1977 u′, 0.4689 v′ in the CIE 1976) consisting of a blue–white and white–yellow thresholds in a tritanopic color confusion line of 21 congenital colorblindness subjects (mean age = 27.7; SD = 5.6 years; 14 deuteranomalous and 7 protanomalous) and of 82 (mean age = 25.1; SD = 3.7 years) normal color vision subjects. Significant increase in the whole tritanopic axis was found for both deuteranomalous and protanomalous subjects compared to controls for the blue–white (F2,100 = 18.80; p < 0.0001) and white–yellow (F2,100 = 22.10; p < 0.0001) thresholds. A Principal Component Analysis (PCA) found a weighting toward to the yellow thresholds induced by deuteranomalous subjects. In conclusion, the discrimination in the tritanopic color confusion axis is significantly reduced in congenital color vision deficiency compared to normal subjects. Since yellow discrimination was impaired the balance of the blue–yellow channels is impaired justifying the increased thresholds found for blue–white discrimination. The weighting toward the yellow region of the color space with the deuteranomalous contributing to that perceptual distortion is discussed in terms of physiological mechanisms.

Color vision was examined in subjects with long-term occupational exposure to mercury (Hg) vapor. The color vision impairment was assessed by employing a quantitative measure of distortion of individual and group perceptual color spaces. Hg subjects (n = 18; 42.1 ± 6.5 years old; exposure time = 10.4 ± 5.0 years; time away from the exposure source = 6.8 ± 4.6 years) and controls (n = 18; 46.1 ± 8.4 years old) were examined using two arrangement tests, D-15 and D-15d, in the traditional way, and also in a triadic procedure. From each subject's 'odd-one-out' choices, matrices of inter-cap subjective dissimilarities were derived and processed by non-metric multidimensional scaling (MDS). D-15d results differed significantly between the Hg-group and the control group (p < 0.05), with the impairment predominantly along the tritan axis. 2D perceptual color spaces, individual and group, were reconstructed, with the dimensions interpreted as the red-green (RG) and the blue-yellow (BY) systems. When color configurations from the Hg-group were compared to those of the controls, they presented more fluctuations along both chromatic dimensions, indicating a statistically significant difference along the BY axis. In conclusion, the present findings confirm that color vision impairments persist in subjects that have received long-term occupational exposure to Hg-vapor although, at the time of testing, they were presenting mean urinary concentration within the normal range for non-exposed individuals. Considering the advantages of the triadic procedure in clinical evaluation of acquired color vision deficiencies, further studies should attempt to verify and/or improve its efficacy.

Purpose To establish fluctuation limits, it was considered that not only overall macular sensitivity but also fluctuations of individual test points in the macula might have clinical value. Methods Three repeated measurements of microperimetry were performed using the Standard Expert test of Macular Integrity Assessment (MAIA) in healthy subjects (N = 12, age = 23.8 ± 1.5 years old) and in patients with age-related macular degeneration (AMD) (N = 11, age = 68.5 ± 7.4 years old). A total of 37 macular points arranged in four concentric rings and in four quadrants were analyzed individually and in groups. Results The data show low fluctuation of macular sensitivity of individual test points in healthy subjects (average = 1.38 ± 0.28 dB) and AMD patients (average = 2.12 ± 0.60 dB). Lower sensitivity points are more related to higher fluctuation than to the distance from the central point. Fixation stability showed no effect on the sensitivity fluctuation. The 95th percentile of the standard deviations of healthy subjects was, on average, 2.7 dB, ranging from 1.2 to 4 dB, depending on the point tested. Conclusion Point analysis and regional analysis might be considered prior to evaluating macular sensitivity fluctuation in order to distinguish between normal variation and a clinical change. Translational relevance Statistical methods were used to compare repeated microperimetry measurements and to establish fluctuation limits of the macular sensitivity. This analysis could add information regarding the integrity of different macular areas and provide new insights into fixation points prior to the biofeedback fixation training.

The aim of the study was to investigate whether there is an ocular interaction in the flicker ERG responses reflecting luminance and cone opponency in normal human subjects. Flicker ERGs were recorded from one dilated eye of 10 healthy volunteers. Each subject was tested twice: once with and once without occluding the opposite eye. Red and green LEDs were modulated in counterphase in a Ganzfeld stimulator. ERG responses were recorded for different ratios of the modulation in the red and green LEDs and at 12 and 36 Hz. The amplitudes and phases of the fundamental components were compared between the conditions with and without occlusion. The 12-Hz flicker ERGs reflected activity of the cone opponent channel, whereas the 36-Hz data reflected luminance activity. There were no significant differences between the conditions with and without occluding the opposite eye for any of the stimulus protocols. Ocular interaction is absent in flicker ERGs reflecting cone opponent and luminance activity.

The silent substitution paradigm offers possibilities to investigate and compare the temporal properties of mechanisms driven by single photoreceptor types, including the critical flicker frequency (CFF), in which the state of adaptation can be kept as invariant. We have (1) measured CFFs using triple silent substitutions to isolate L-, M-, and S-cone as well as rod-driven pathways under identical mean luminances and chromaticities; (2) repeated the CFF measurements at different mean luminances in order to validate the Ferry-Porter law (stating that the relationship between CFF and the log retinal illuminance-log I-is linear); and (3) compared these CFF versus log I functions for L-, M-, S-cone-, and rod-isolating stimuli for five trichromats and four X-linked dichromats (two protanopes, two deuteranopes). We show that the effects of luminance on the CFFs with silent substitution are comparable to those measured previously with chromatic stimuli. We found that M-cone-driven CFFs are smaller in trichromats than in protanopes. Furthermore, the slopes of the M-cone-driven CFF versus log I functions are smaller in trichromats. Possibly, the lacking L-cones are replaced by M-cones in these two protanopes and the CFF depends on cone density. Furthermore, we found that in trichromats, the slopes of the CFF-log I functions are smaller for M-cone- than for L-cone-isolating stimuli. This contradicts the current interpretation of the CFF-log I functions for chromatic stimuli, which states that CFF is mediated by the most strongly modulated photoreceptor type. Thus, the larger slopes that were previously found with medium-wavelength chromatic stimuli compared with long-wavelength chromatic stimuli seem to be the result of an addition of signals from different photoreceptors and do not necessarily result from M-cones being inherently faster.

Sao Paulo Research Foundation (FAPESP) [2014/26818-2, 2014/50457-0, 2016/04538-3, 2014/06457-5, 2015/22227-2, 2016/22007-5] National Council for Scientific and Technological Development (CNPq) [480428/2013-4, 470785/2014-4, 404239/2016-1] CAPES [3263/2013] Janos Bolyai Scholarship of the Hungarian Academy of Sciences PURPOSE: Smith-Magenis syndrome (SMS) causes sleep disturbance that is related to an abnormal melatonin profile. It is not clear how the genomic disorder leads to a disturbed synchronization of the sleep/wake rhythm in SMS patients. To evaluate the integrity of the intrinsically photosensitive retinal ganglion cell (ipRGC)/melanopsin system, the transducers of the light-inhibitory effect on pineal melatonin synthesis, we recorded pupillary light responses (PLR) in SMS patients. METHODS: Subjects were SMS patients (n = 5), with molecular diagnosis and melatonin levels measured for 24 hours and healthy controls (n = 4). Visual stimuli were 1-second red light flashes (640 nm insignificant direct ipRGC activation), followed by a 470-nm blue light, near the melanopsin peak absorption region (direct ipRGC activation). Blue flashes produce a sustained pupillary constriction (ipRGC driven) followed by baseline return, while red flashes produce faster recovery. RESULTS: Pupillary light responses to 640-nm red flash were normal in SMS patients. In response to 470-nm blue flash, SMS patients had altered sustained responses shown by faster recovery to baseline. SMS patients showed impairment in the expected melatonin production suppression during the day, confirming previous reports. CONCLUSIONS: SMS patients show dysfunction in the sustained component of the PLR to blue light. It could explain their well-known abnormal melatonin profile and elevated circulating melatonin levels during the day. Synchronization of daily melatonin profile and its photoinhibition are dependent on the activation of melanopsin. This retinal dysfunction might be related to a deficit in melanopsin-based photoreception, but a deficit in rod function is also possible. Univ Sao Paulo, Dept Expt Psychol, Inst Psychol, Sao Paulo, Brazil Semmelweis Univ, Dept Ophthalmol, Budapest, Hungary Univ Sao Paulo, Dept Neurol, Fac Med, Sao Paulo, Brazil Budapest Univ Technol & Econ, Dept Mechatron Opt & Engn Informat, Budapest, Hungary Univ Texas San Antonio, Dept Cellular & Struct Biol, San Antonio, TX USA Univ Fed Sao Paulo, Dept Physiol, Sao Paulo, Brazil Univ Sao Paulo, Dept Physiol & Biophys, Inst Biomed Sci, Av Lineu Prestes 1524, BR-05508000 Sao Paulo, SP, Brazil Univ Fed Sao Paulo, Dept Physiol, Sao Paulo, Brazil FAPESP [2014/26818-2, 2014/50457-0, 2016/04538-3, 2014/06457-5, 2015/22227-2, 2016/22007-5] CNPq [480428/2013-4, 470785/2014-4, 404239/2016-1] CAPES [3263/2013] Web of Science

This longitudinal study addresses the reversibility of color vision losses in subjects who had been occupationally exposed to mercury vapor. Color discrimination was assessed in 20 Hg-exposed patients (mean age = 42.4 ± 6.5 years; 6 females and 14 males) with exposure to Hg vapor during 10.5 ± 5.3 years and away from the work place (relative to 2002) for 6.8 ± 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 ± 35.4 μg/g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 (Ventura et al., 2005), but at the time of the follow-up tests, in 2005, this value was 1.4 ± 1.4 μg/g creatinine for patients compared with 0.5 ± 0.5 μg/g creatinine for controls (different group from the one in Ventura et al. (2005)). Color vision was monocularly assessed using the Cambridge Colour Test (CCT). Hg-exposed patients had significantly worse color discrimination (p < 0.02) than controls, as evaluated by the size of MacAdam's color discrimination ellipses and color discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. (2005) and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation (Ventura et al., 2005) and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, color vision impairment remains irreversible.

Objetivo. Avaliar o campo visual em ex-trabalhadores de fábricas de lâmpadas fluorescentes com diagnóstico de mercurialismo metálico crônico ocupacional, através de testes psicofísicos de campimetria computadorizada e registros eletrofisiológicos da retina obtidos através do eletrorretinograma multifocal. Método. A avaliação psicofísica do campo visual foi realizada em 35 ex-trabalhadores (idade média = 44,2 ± 5,9 anos; 30 homens) no equipamento Humphrey Field Analyzer II (modelo 750i) em dois testes: acromático (standard automated perimetry) e azul-amarelo (short wavelength automated perimetry). O programa Visual Evoked Response Imaging System (VERISTM Science 5.0) permitiu o registro e análise dos sinais eletrofisiológicos da retina através do eletrorretinograma multifocal em 32 ex-trabalhadores (idade média = 44,6 ± 5,5 anos; 27 homens) dos 35 que realizaram os testes de campimetria computadorizada. Os resultados foram comparados com um grupo controle para o campo visual (n = 34; idade média = 43,3 ± 8,3 anos; 21 homens) e com outro grupo controle para o eletrorretinograma multifocal (n = 21; idade média = 43,5 ± 8,9 anos; 10 homens). Resultados. Os exames psicofísicos de campimetria computadorizada mostraram que há redução da sensibilidade visual em regiões centrais até 27? do campo visual. No exame acromático a diminuição da sensibilidade ocorreu, inclusive, na região foveal. O exame azul-amarelo confirmou a redução encontrada no exame acromático para regiões paracentrais até 27° de excentricidade. O eletrorretinograma multifocal apresentou redução nas amplitudes das respostas retinianas em regiões centrais até 25°, sem alteração no tempo implícito das respostas. As regiões paracentrais mostraram redução significativa para os valores de amplitude do primeiro componente negativo (N1) e do primeiro componente positivo (P1). Discussão. A redução na sensibilidade visual em diferentes regiões do campo visual, confirma que há prejuízos no sistema visual decorrentes da exposição crônica ao vapor de mercúrio. Nesse caso, não se pode especificar as regiões afetadas, porque a metodologia utilizada não permite isolar estruturas da via visual e, consequentemente, não permite localizar as regiões específicas que o mercúrio estaria prejudicando preferencialmente. Os prejuízos causados pela intoxicação ao vapor de mercúrio na retina parecem ser difusos, considerando que a redução de amplitude das respostas de N1 e P1 pode indicar prejuízos em diferentes grupos celulares da retina. Os resultados mostram que parte dos prejuízos de campo visual causados pelo vapor de mercúrio estão relacionados com alterações retinianas. Os resultados estão de acordo com trabalhos preliminares que monstraram alterações visuais que permanecem mesmo anos após o afastamento da fonte de exposição, sugerindo que a intoxicação por vapor de mercúrio pode não ser totalmente reversível. Conclusão. Os sujeitos expostos cronicamente ao vapor de mercúrio durante um período de 10 anos (em média) apresentam redução da sensibilidade visual em diferentes regiões do campo visual, mesmo após 7 anos (em média) de afastamento da fonte expositora. Pode haver prejuízos em diferentes regiões da via visual envolvidos nas alterações de campo visual, mas parte desses prejuízos causados pela exposição crônica ocupacional ao vapor de mercúrio possui origem retiniana. Purpose. To analyse visual field sensitivity in a group of workers retired from thefluorescent lamp industry diagnosed with chronic occupational metallic mercurialism using psychophysical tests such as automated perimetry and measuring the retina cells\' electrical responses with the multifocal electroretinogram. Methods. The psychophysical evaluation of the visual field was performed in 35 retired workers (mean age = 44.2 ± 5.9 years; 30 males) using Humphrey Field Analyzer II (model 750i) device in two different tests: SAP (standard automated perimetry) and SWAP (short wavelength automated perimetry). The Visual Evoked Response Imaging System (VERISTM Science 5.0) provided us the electrophysiological recordings and analysis of the retina based on measurement data from the multifocal electroretinogram in 32 retired workers (mean age = 44.6 ± 5.5 years; 27 males) that were included in the 35 automated perimetry test subjects. The results were compared with an age-matched control group using the visual field tests (n = 34; mean age = 43.3 ± 8.3 years; 21 males) and to another age-matched control group at the multifocal electroretinogram (n = 21; mean age = 43.5 ± 8.9 years; 10 males). Results. The automated perimetry tests have shown visual sensitivity reductions in the central areas around 27° of eccentricity. In the SAP test sensitivity decrease was found even in the foveal region. The SWAP test results are in agreement with the reduction found around 27° in the SAP test at mid-peripheral areas. The multifocal electroretinogram has shown decreases in amplitude in the retina recordings in the central areas around 25° of eccentricity, but there were no implicit time reductions. The mid-peripheral areas have shown significant reductions in the amplitude values in the first negative component (N1) and in the first positive component (P1) as well. Discussion. The visual sensitivity reductions in the different visual field areas confirm the visual damages in patients with long-term mercury vapor exposure. In this case the affected visual pathway sections could not be determined since the applied psychophysical method does not allow us to indicate the specific visual structure principally damaged by the mercury vapor. The damages found in the retina due to mercury vapor intoxication can be considered broadly dispersed, since the reductions in N1 and P1 amplitudes might be the indications of damages in multiple retina cell groups. Our results show that some visual field losses are related to various retinal alterations caused by the mercury vapor. The results are in agreement with preliminary works that showed visual dysfunctions after several years away from the mercury vapor source suggesting that mercury vapor intoxication may not be completely reversible. Conclusion. The long-term (10 years in average) mercury vapor exposed workers have shown visual sensitivity reductions in different visual field areas after 7 years (in average) away from the mercury vapor source. In our present study we would like to indicate that visual field reductions cannot only be related to damages in the various sections of the visual pathway, but some of these visual field losses can occur due to retinal alterations caused by cronic mercury vapor exposure.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that can modulate cortical activity. Nonetheless, information regarding its functional specificity and the extent by which visual performance can be modulated is still lacking. Here, we used vision as model to address if it differentially affects different cell groups in the stimulated area. We applied tDCS to the occiput and performed a series of visual tests in a sham-controlled repeated-measures design. Achromatic contrast sensitivity was assessed psychophysically during tDCS, with tasks designed to target specific spatial frequency (SF) channels, inferred ON, OFF channels and inferred magnocellular and parvocellular pathways of the visual system. Sweep visual evoked potential (sVEP) for contrast sensitivity and Vernier acuity was recorded before and after tDCS. Anodal tDCS significantly increased thresholds for luminance decrements (OFF) only for the inferred magnocellular thresholds. Although tDCS had no significant effects on Vernier or contrast sVEP thresholds, it modulated suprathreshold amplitudes for both tasks. Cathodal tDCS increased sVEP amplitudes at a low SF, decreased it at a medium, and had no effect at a high SF. Cathodal tDCS increased sVEP phase lags for low and decreased it for high SF (maximum change corresponding to change in apparent latency >6 ms). Cathodal and anodal stimulation decreased amplitudes of sVEP Vernier responses. Exclusive tDCS effects on magnocellular thresholds agree with reports of pathway-specific tDCS effects. The dependence of tDCS effects on SF and contrast levels further suggests that tDCS differentially affects different cell groups in the visual cortex.

Purpose Visual information is processed in parallel pathways in the visual system. Parallel processing begins at the synapse between the photoreceptors and their postreceptoral neurons in the human retina. The integrity of this first neural connection is vital for normal visual processing downstream. Of the numerous elements necessary for proper functioning of this synaptic contact, dystrophin proteins in the eye play an important role. Deficiency of muscle dystrophin causes Duchenne muscular dystrophy (DMD), an X-linked disease that affects muscle function and leads to decreased life expectancy. In DMD patients, postreceptoral retinal mechanisms underlying scotopic and photopic vision and ON- and OFF-pathway responses are also altered. Methods In this study, we recorded the electroretinogram (ERG) while preferentially activating the (red-green) opponent or the luminance pathway, and compared data from healthy participants (n = 16) with those of DMD patients (n = 10). The stimuli were heterochromatic sinusoidal modulations at a mean luminance of 200 cd/m2. The recordings allowed us also to analyze ON and OFF cone-driven retinal responses. Results We found significant differences in 12-Hz response amplitudes and phases between controls and DMD patients, with conditions with large luminance content resulting in larger response amplitudes in DMD patients compared to controls, whereas responses of DMD patients were smaller when pure chromatic modulation was given. Conclusions The results suggest that dystrophin is required for the proper function of luminance and red-green cone opponent mechanisms in the human retina.

Previous research showed that Transcranial Direct Current Stimulation (tDCS) can modulate visual cortex excitability. However, there is no experiment on the effects of tDCS on color perception to date. The present study aimed to investigate the effects of tDCS on color discrimination tasks. 15 healthy subjects (mean age of 25.6 ± 4.4 years) were tested with Cambridge Color Test 2.0 (Trivector and Ellipses protocols) and a Forced-choice Spatial Color Contrast Sensitivity task (vertical red-green sinusoidal grating) while receiving tDCS. Anodal, cathodal and sham tDCS were delivered at Oz for 22 minutes using two square electrodes (25cm2 with a current of 1.5mA) in sessions separated by 7 days. Anodal tDCS significantly increased tritan sensitivity (p

PURPOSE To measure heterochromatic flicker electroretinograms (ERGs) at high (36 Hz) and intermediate (12 Hz) temporal frequencies to evaluate luminance and cone opponent responses, respectively, in glaucoma eyes with (perimetric) and without (preperimetric) visual field defects. METHODS Flicker ERGs were recorded from one randomly chosen dilated eye of 32 patients (mean age, 61 ± 11 years; 15 men, 17 women) from the Erlangen Glaucoma Registry and from 24 healthy volunteers (mean age, 43 ± 11 years; 14 men, 10 women). Red and green light-emitting diodes in a Ganzfeld stimulator were sine wave-modulated in counterphase. The responses were measured at 36 Hz, the frequency at which ERGs reflect activity of the luminance pathway, and at 12 Hz, the frequency at which ERGs reflect chromatic activity. RESULTS Response amplitudes were similar in glaucoma patients and controls. Phase differences were observed in patients with visual field defects (perimetric) compared with the control group at 36 and 12 Hz in the first harmonic and second harmonic responses. Patients without visual field defects (preperimetric) showed phase differences for the second harmonic component at 36 Hz. No age effect on response amplitudes and phases was found in any of the subject groups (controls and patients). CONCLUSIONS The responses displayed phase differences but not amplitude differences in perimetric glaucoma patients at both 36 and 12 Hz, suggesting that both magnocellular and parvocellular pathways are affected. Preperimetric glaucoma patients also showed phase differences. The response phase may be sensitive to early dysfunction of the inner retina. (ClinicalTrials.gov number, NCT00494923).

In children with Duchenne muscular dystrophy, color vision losses have been related to dystrophin deletions downstream of exon 30, which affect a dystrophin isoform, Dp260, present in the retina. To further evaluate visual function in DMD children, we measured spatial, temporal, and chromatic red-green and blue-yellow contrast sensitivity in two groups of DMD children with gene deletion downstream and upstream of exon 30. Psychophysical spatial contrast sensitivity was measured for low, middle, and high spatial frequencies with achromatic gratings and for low and middle frequencies with red-green and blue-yellow chromatic gratings. Temporal contrast sensitivity was also measured with achromatic stimuli. A reduction in sensitivity at all spatial luminance contrasts was found for the DMD patients with deletion downstream of exon 30. Similar results were found for temporal luminance contrast sensitivity. Red-green chromatic contrast sensitivity was reduced in DMD children with deletion downstream of exon 30, whereas blue-yellow chromatic contrast sensitivity showed no significant differences. We conclude that visual function is impaired in DMD children. Furthermore, we report a genotype-phenotype relationship because the visual impairment occurred in children with deletion downstream but not upstream of exon 30, affecting the retinal isoform of dystrophin Dp260.

The study investigated possible asymmetric dysfunction of the ON and OFF visual mechanisms in DMD (Duchenne muscular dystrophy) patients associated with specific genetic alterations.nineteen DMD patients and 7 heterozygous dmd carriers were tested, as well as 19 age-matched controls.Full-field ergs were recorded using mesopic (1 cd/m(2)) and photopic (250 cd/m(2)) sawtooth luminance modulations as stimuli: rapid increase and ramping decrease (to isolate ON responses) or rapid decrease and ramping increase (for OFF responses). In addition, a psychophysical study comprised contrast sensitivity tests using two checkerboard stimuli at either higher (ON) or lower (OFF) luminance relative to the background: 0.3 cycles per degree (cpd) presented for 33 ms (low spatial frequency, short duration) and 2 cpd presented for 1500 ms (high spatial frequency, long duration).A significant ERG amplitude reduction, relative to controls, was detected in the DMD patients in the mesopic positive peaks for both ON and OFF stimuli, as well as for the photopic ON stimulus (P0.05). Contrast sensitivity was significantly lower in the DMD patients (P0.05) relative to controls for the ON stimuli. Neither the ERG nor the contrast sensitivities were altered in the carriers.This study suggests that there are ON and OFF ERG alterations when both rods and cones contribute to the ERG responses in DMD patients. When only cones are activated there is an asymmetrical ERG alteration, also revealed by the contrast sensitivity measurements.

The purpose of the present study was to measure contrast sensitivity to equiluminant gratings using steady-state visual evoked cortical potential (ssVECP) and psychophysics. Six healthy volunteers were evaluated with ssVECPs and psychophysics. The visual stimuli were red-green or blue-yellow horizontal sinusoidal gratings, 5° × 5°, 34.3 cd/m2 mean luminance, presented at 6 Hz. Eight spatial frequencies from 0.2 to 8 cpd were used, each presented at 8 contrast levels. Contrast threshold was obtained by extrapolating second harmonic amplitude values to zero. Psychophysical contrast thresholds were measured using stimuli at 6 Hz and static presentation. Contrast sensitivity was calculated as the inverse function of the pooled cone contrast threshold. ssVECP and both psychophysical contrast sensitivity functions (CSFs) were low-pass functions for red-green gratings. For electrophysiology, the highest contrast sensitivity values were found at 0.4 cpd (1.95 ± 0.15). ssVECP CSF was similar to dynamic psychophysical CSF, while static CSF had higher values ranging from 0.4 to 6 cpd (P < 0.05, ANOVA). Blue-yellow chromatic functions showed no specific tuning shape; however, at high spatial frequencies the evoked potentials showed higher contrast sensitivity than the psychophysical methods (P < 0.05, ANOVA). Evoked potentials can be used reliably to evaluate chromatic red-green CSFs in agreement with psychophysical thresholds, mainly if the same temporal properties are applied to the stimulus. For blue-yellow CSF, correlation between electrophysiology and psychophysics was poor at high spatial frequency, possibly due to a greater effect of chromatic aberration on this kind of stimulus.

The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6±6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24–2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann–Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p

A retina é formada por camadas de células que a estrutura, os contatos sinápticos e as características fisiológicas são específicas para cada tipo de célula. O processamento da informação visual, após a ativação dos fotorreceptores pela luz, ocorre em mecanismos pós-receptorais que formam diferentes circuitos de processamento, entre eles as vias ON, OFF, de luminância e de oponência cromática. As doenças que afetam a retina podem estar relacionadas com alterações específicas de um determinado circuito, como acontece com a distrofia muscular de Duchenne (DMD) que na alteração do gene dmd da retina afeta a comunicação entre os fotorreceptores e as células bipolares, e na diabetes Mellitus (DM) o dano celular ocorre principalmente na camada mais interna da retina. O objetivo deste estudo foi avaliar os efeitos da DMD e da diabetes Mellitus Tipo 1 (DM1) em diferentes mecanismos visuais. A amostra deste trabalho contou com três grupos: controle com 18 participantes (13,5, ±7,6), DMD com 9 participantes (16, ±5,9) e DM1 com 12 partcipantes (13,8, ±2,5). Os testes eletrorretinográficos foram aplicados nas condições mesópica, fotópica com estímulos que enfatizam respostas ON ou OFF, e flicker heterocromático (verde-vermelho) em 12Hz (para enfatizar a atividade da via de oponência cromática) e 36Hz (para enfatizar a atividade da via de luminância), e testes psicofísicos com estímulos que enfatizam os mecanismos ON e OFF com contraste de luminância e a via de oponência cromática por um estímulo com contraste cromático (isoluminante) verde-vermelho. O grupo DMD apresentou alteração no tempo de resposta e redução na amplitude da onda-a e onda-b nas condições mesópicas ON e OFF, redução da amplitude da onda-b na condição fotópica ON e alteração da via cromática. Enquanto o grupo DM1 apresentou aumento na amplitude e tempo da ond-a e onda-b das via ON e OFF na condição mesópica, mudança na fase da resposta na via cromática e na via de luminância. Os resultados estão de acordo com diversos estudos anteriores que mostram que as duas doenças causam alterações funcionais na retina, mas cada doença com características específicas. O presente estudo demonstrou que as duas doenças afetam as vias visuais ON e OFF independente do prejuízo neural ocorrer principalmente nas camadas mais externas ou nas camadas mais internas da retina. A possibilidade de identificar prejuízos funcionais em pacientes sem alteração clínica é uma valiosa ferramenta para o acompanhamento de doenças e para avaliar a eficácia de tratamentos. O presente estudo poderá contribuir para o estabelecimento de novos protocolos mais sensíveis e capazes de identificar alterações assimétricas no caso da DMD ou alterações que precedem o diagnóstico clínico no caso da DM1 The retina is formed by layers of cells that the structure, synaptic contact and physiology characters are specific for each type of this cells. The processing of visual information, after the photoreceptor activation by light is separate by post-receptor mechanisms that constitute the ON, OFF, luminance and chromatic pathways. The retina diseases have specific alteration in this tissue, thus it happens with the Duchenne muscular dystrophy (DMD), that have communication problems among photoreceptors and bipolar cells because of damage in dmd gene, and the Diabetes Mellitus (DM) that has cells damage mainly in the inner layer of retina. The purpose of this study was to evaluate the effects of DMD and Type 1 diabetes Mellitus (DM1) on different visual mechanisms. The sample had three grups: control with 18 subjects (13.5, ±7.6), DMD with 9 subjects (16, ±5.9) and DM1 with 12 subjects (13,8, ±2,5). The ERG recordings were applied in of the mesopic and photopic conditions with stimuli that laid emphasis on ON and OFF responses and heterochromatic (red-green) flicker modulation in 12Hz (laid emphasis on chromatic pathway) and 36Hz (laid emphasis on luminance pathway), and psychophysical tests laid emphasis on ON and OFF mechanisms with luminance contrast and the chromatic opponent pathway by stimulus with red-green chromatic contrast (isoluminance). As a result the DMD group presented alteration in the response time and reduction in the amplitude of the a- and b-wave in ON and OFF mesopic conditions, reduction of the amplitude of the a- and b-wave in ON photopic condition and alteration of the chromatic pathway. While the DM1 group showed an increase in the amplitude and time of the a- and b-wave in ON and OFF pathways of the mesopic condition, change in phase of the chromatic pathway and luminance pathway. These results were in agreement with previous studies that showed the two diseases present functional changes in the retina, but each disease with specific characteristics. The present study showed that two diseases affect the ON and OFF pathways regardless of the neural damage occur mainly in outer layer or inner layer of the retina. The possibility identify functional damage in patients without clinic injuries is the valuable tool for the following the dieses and evaluated treatment efficiency. The present study may contribute to establishment of the new sensitive and able protocols to identify asymmetric changes in DMD or changes that precede the clinical diagnosis in DM1