Search

PURPOSE: Timely receipt of mammograms to screen for breast cancer in accordance with the United States Preventive Services Task Force (USPSTF) recommendations can substantially reduce morbidity and mortality. The purpose of this study is to assess whether odds of receiving screening mammograms are similar for women with and without visual impairment. DESIGN: Retrospective longitudinal cohort study. PARTICIPANTS: 1044 females, 65–72 years of age, enrolled in fee-for-service Medicare from January 1, 2008 to December 31, 2015. METHODS: We matched patients with no vision loss (NVL), partial vision loss (PVL), and severe vision loss (SVL) 1:1:1 based on age, race, time in Medicare, urbanicity of residence, and overall health. Women with pre-existing breast cancer were excluded. Multivariable conditional logistic regression modeling compared the odds of receiving screening mammography within a 2-year follow-up period among the 3 groups. MAIN OUTCOMES MEASURES: Proportion receiving mammography and adjusted odds ratios (OR) of receiving mammography within 2 years of follow-up among the groups. RESULTS: A total of 1044 patients were matched (348 in each group). The mean ± SD age at the index date was 69.0 ± 1.5 years for all 3 groups. The proportion of women receiving ≥ 1 mammogram within the 2-year follow-up period was 69.0% (n=240), 56.9% (n=198), and 56.0% (n=195) for the NVL, PVL and SVL groups, respectively (p=0.0005). The mean ± SD number of mammograms received per patient during the 5-year period (3-year look-back plus 2-year follow-up period) was 3.1 ± 2.0, 2.5 ± 2.0, and 2.3 ± 2.1 for the NVL, PVL and SVL groups, respectively (p

Adherence to medication treatment protocols and active participation by individuals in their medical care are important for all patients, but especially for those with chronic conditions such as vision loss. Adherence is crucial for decreasing avoidable vision loss. Failure to take medications as prescribed and keep scheduled appointments reduces treatment effectiveness, increases complications and results in poorer outcomes. Reasons for nonadherence vary by diagnosis and include not understanding the importance of adherence, low health literacy, lack of adequate self-efficacy, low level of activation and behavioral issues including depression. Patients may lack information about their condition and its prognosis, available treatment alternatives, and other essential information such as how to monitor their eye condition, what to do if vision deteriorates and how to get needed community-based help. Each of these factors impedes patients' ability to engage with their physician and participate in their own care. The ability of individuals with vision loss to actively and effectively manage their health care, ie, activation, has been understudied. When patients are involved with their own care, their care experience, and most importantly, their outcomes, are improved. Identifying antecedents of adherence may help provide disease- and patient-specific pathways to reduce avoidable vision loss.

Advanced wearable devices are increasingly incorporating high-resolution multi-camera systems. As state-of-the-art neural networks for processing the resulting image data are computationally demanding, there has been growing interest in leveraging fifth generation (5G) wireless connectivity and mobile edge computing for offloading this processing to the cloud. To assess this possibility, this paper presents a detailed simulation and evaluation of 5G wireless offloading for object detection within a powerful, new smart wearable called VIS4ION, for the Blind-and-Visually Impaired (BVI). The current VIS4ION system is an instrumented book-bag with high-resolution cameras, vision processing and haptic and audio feedback. The paper considers uploading the camera data to a mobile edge cloud to perform real-time object detection and transmitting the detection results back to the wearable. To determine the video requirements, the paper evaluates the impact of video bit rate and resolution on object detection accuracy and range. A new street scene dataset with labeled objects relevant to BVI navigation is leveraged for analysis. The vision evaluation is combined with a detailed full-stack wireless network simulation to determine the distribution of throughputs and delays with real navigation paths and ray-tracing from new high-resolution 3D models in an urban environment. For comparison, the wireless simulation considers both a standard 4G-Long Term Evolution (LTE) carrier and high-rate 5G millimeter-wave (mmWave) carrier. The work thus provides a thorough and realistic assessment of edge computing with mmWave connectivity in an application with both high bandwidth and low latency requirements., Published in: IEEE Access ( Volume: 10)

Significance Systematic lighting assessments should be part of low vision evaluations. The LuxIQ has gained popularity as an assessment tool, but its reliability has not been examined independently and is necessary for evidence-based vision rehabilitation. Purpose Besides magnification, improved lighting levels are a common intervention in reading rehabilitation for individuals with low vision. Determining the appropriate lighting can be a complex and time-consuming task. The LuxIQ is a portable lighting assessment tool that can be used to systematically measure lighting preferences; however, there is little independent evidence to support its reliability in low vision rehabilitation. Methods One hundred nine control subjects (age, 18 to 85 years) and 64 individuals with low vision (age, 27 to 99 years) adjusted both the luminance and color temperature parameters on the LuxIQ while viewing a sentence on the MNREAD at their preferred print size for continuous reading. After 30 minutes, they were asked to repeat the same measurements. Results Using Bland-Altman plots, test-retest variability was calculated using the limits of agreement (LOAs). For illuminance, the LOA width was 2806 lux for control subjects and 2657 lux for visually impaired participants. For color temperature, the LOA width was 2807 K for control subjects and 2364 K for those with a visual impairment. Difference scores were centered near zero, indicating overall accuracy. Conclusions The measurement of lighting preference lacks the precision necessary for clinical utility, given that the LOA for luminance ranged more than 2600 lux, with normally sighted and low vision participants. Such variability translates into a range of approximately ±40 or 50 W in an incandescent light bulb, depending on the luminance level, making it clinically difficult to narrow down the options for evidence-based lighting recommendations. Next steps are to examine whether the reading behavior of low vision clients is positively affected by interventions that are based on LuxIQ recommendations.

OBJECTIVE. We sought to determine under what conditions brighter lighting improves reading performance. METHOD. Thirteen participants with typical sight and 9 participants with age-related macular degeneration (AMD) read sentences ranging from 0.0 to 1.3 logMAR under luminance levels ranging from 3.5 to 696 cd/m2. RESULTS. At the dimmest luminance level (3.5 cd/m2), reading speeds were slowest at the smaller letter sizes and reached an asymptote for larger sizes. When luminance was increased to 30 cd/m2, reading speed increased only for the smaller letter sizes. Additional lighting did not increase reading speeds for any letter size. Similar size-related effects of luminance were observed in participants with AMD. CONCLUSION. In some instances, performance on acuity-limited tasks might be improved by brighter lighting. However, brighter lighting does not always improve reading; the magnitude of the effect depends on the text size and the relative changes in light level.

IMPORTANCE: Patients with vision loss who are hospitalized for common illnesses are often not identified as requiring special attention. This perception, however, may affect the outcomes, resource use, and costs for these individuals. OBJECTIVE: To assess whether the mean hospitalization lengths of stay, readmission rates, and costs of hospitalization differed between individuals with vision loss and those without when they are hospitalized for similar medical conditions. DESIGN, SETTING, AND PARTICIPANTS: This analysis of health care claims data used 2 sources: Medicare database and Clinformatics DataMart. Individuals with vision loss were matched 1:1 to those with no vision loss (NVL), on the basis of age, years from initial hospitalization, sex, race/ethnicity, urbanicity of residence, and overall health. Both groups had the same health insurance (Medicare or a commercial health plan), and all had been hospitalized for common illnesses. Vision loss was categorized as either partial vision loss (PVL) or severe vision loss (SVL). Data were analyzed from April 2015 through April 2018. MAIN OUTCOMES AND MEASURES: The outcomes were lengths of stay, readmission rates, and health care costs during hospitalization and 90 days after discharge. Multivariable logistic and linear regression models were built to identify factors associated with these outcomes among the NVL, PVL, and SVL groups. RESULTS: Among Medicare beneficiaries, 6165 individuals with NVL (with a mean [SD] age of 82.0 [8.3] years, and 3833 [62.2%] of whom were female) were matched to 6165 with vision loss. Of those with vision loss, 3401 (55.2%) had PVL and 2764 (44.8%) had SVL. In the Clinformatics DataMart database, 5929 individuals with NVL (with a mean [SD] age of 73.7 [15.1] years, and 3587 [60.5%] of whom were female) were matched to 5929 individuals with vision loss. Of the commercially insured enrollees with vision loss, 3515 (59.3%) had PVL and 2414 (40.7%) had SVL. Medicare enrollees with SVL, compared with those with NVL, had longer mean lengths of stay (6.48 vs 5.26 days), higher readmission rates (23.1% vs 18.7%), and higher hospitalization and 90-day postdischarge costs ($64 711 vs $61 060). Compared with those with NVL, Medicare beneficiaries with SVL had 4% longer length of stay (estimated ratio, 1.04; 95% CI, 1.01-1.07; P = .02), 22% higher odds of readmission (odds ratio, 1.22; 95% CI, 1.06-1.41; P = .007), and 12% higher costs (estimated cost ratio, 1.12; 95% CI, 1.06-1.18; P

Patients with macular disease and central visual loss affecting the fovea often adopt an eccentric preferred retinal location (PRL). The existence of eccentric PRLs has been known for many years1; however, their characteristics are still not fully understood. Studies have shown that their location can change as a function of the type of macular disease, the luminance level, and the functional task.2-6 Information as to their location and stability is not only useful for the clinician in planning future treatment of patients with macular disease but also is essential for the correct interpretation of measures of local function such as visual field sensitivity and focal or multifocal electroretinography. The information may also prove to be an indicator of disease progression. Recently a microperimeter, the Nidek microperimeter (MP-1) (Nidek Technologies Inc., Padova, Italy) has been developed that may be a useful clinical tool for assessing the location and stability of fixation while simultaneously measuring visual field sensitivity. The MP-1 combines fundus tracking microperimetry with color fundus photography. The examiner selects a landmark with high reflectivity on the fundus and stimuli are projected onto the retina in relation to this landmark using an LCD. An automatic eye tracker compensates for eye movements. A color fundus photograph is taken at the end of the examination and a registration technique is used to overlay the perimetric and fixation results on the fundus photograph. This allows visual function to be compared to retinal morphology. The technique has the potential to improve our understanding of PRLs and of visual sensitivity of the surrounding areas of patients with macular disease. In this study the MP-1 and conventional fundus photography were used to investigate the location and fixation stability of PRLs in a group of patients with retinal disease affecting the macula. The visual sensitivity of the surrounding retinal region was measured with static perimetry and the relationship of the PRL to fundus abnormalities examined by overlaying the perimetric and fixation results onto the fundus photograph and onto the fundus autofluorescence (FAF) images. Finally the effect of an eccentric PRL on the interpretation of the results of functional tests such as the multifocal electroretinogram is discussed.

Purpose To determine whether retinal dysfunction in obligate carriers of X-linked retinoschisis (XLRS) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). Methods Nine obligate carriers of XLRS (mean age, 46.2 years) were examined for the study. Examination of each carrier included an ocular examination and mfERG testing. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40° in diameter. The amplitudes and implicit times in each location for the mfERG were compared with the corresponding values determined for a group of 34 normally-sighted, age-similar control subjects. Results Mapping of 103 local electroretinographic response amplitudes and implicit times within a central 40° area with the mfERG showed regions of reduced mfERG amplitudes and delayed implicit times in two of nine carriers. Conclusions The mfERG demonstrated areas of retinal dysfunction in two carriers of XLRS. When present, retinal dysfunction was evident in the presence of a normal-appearing fundus. Multifocal ERG testing can be useful for identifying some carriers of XLRS.

We examined the effects of inter-modal attention and mental arithmetic on Humphrey visual field sensitivity and multifocal visual evoked potential (mfVEP) amplitude. Four normally sighted subjects (ages ranging from 24 to 58years) participated in this study. Monocular visual field sensitivity was measured under two conditions: (1) standard testing condition and (2) while the subject performed a Paced Auditory Serial Addition Task (PASAT). Monocular mfVEPs were recorded in response to a 60-sector stimulus. The checkerboard pattern in each sector was contrast reversed according to a binary m-sequence. mfVEPs were recorded under two conditions: (1) standard testing conditions and (2) while the subject performed a PASAT. We found that, when compared to the no-task condition, all subjects had locations of significantly reduced Humphrey visual field sensitivities when performing the PASAT. In contrast, there were no significant decreases in mfVEP amplitude in any sector for any of the subjects while performing the PASAT. Our findings indicate that divided attention and ongoing mental processes did not affect the mfVEP. Therefore, the mfVEP provides an objective measure of visual field function that may be useful for some patients with unreliable automated static perimetry results.

The multifocal electroretinogram (mfERG) has been commonly used as a method for obtaining objective visual fields. Although qualitative comparisons have been good, quantitative comparisons between the results from mfERG and the results from Humphrey Visual Field Analyser (HVFA) have found variable degrees of agreement depending upon the mfERG response parameter examined and/or the disease studied. Lack of agreement may be due to differences in methodology, differences in the sites of response generation, and/or differences derived from comparing suprathreshold versus threshold responses. In addition, the two procedures are performed at different levels of adaptation. We developed an approach for matching stimulus parameters and compared mfERG and psychophysical thresholds to assess the effects of technique and level of adaptation on the two responses. Psychophysical and mfERG thresholds were obtained as a function of the adaptation level (1.5–4.0 log td) and retinal location. The derived increment threshold-versus-intensity functions for both measures were fitted using the equation log T =log T 0 +log(( A + A 0 )/ A 0 ) n . We found that the values of A 0 for the mfERG data were one log unit higher than those for the psychophysical data. In addition, the value of the slope ( n ) for the mfERG data was shallower (0.8) than that of the psychophysical data (1.0). Predictions were made about comparisons of HVFA threshold and mfERG amplitude data in patients with retinal disease based upon a two-site model of adaptation. The data for some groups of patients could be best-fitted with a model of a disease acting at a site distal to all gain changes, whereas data from other patients were best fitted with a model of a disease acting at a site proximal to all retinal gain. The relationship between the Humphrey visual field threshold losses and mfERG amplitude reductions depends upon the site and mechanism of a particular disease process and the model of retinal gain assumed. In no case is a one-to-one relationship between the losses in the two measures predicted.

Previous studies have found an increase in peripheral target localization errors in normally sighted older adults. These results have been interpreted as indicative of a constriction of the "useful field of view". In the present study, we parametrically manipulated masking, distractors and stimulus luminance and examined the relationships between peripheral target localization and age. We found that backward masking and/or flashed distractors increased error rates. This decrement in performance was larger for more peripherally located targets and largest for the older subjects at all stimulus locations. Stimulus luminance (either 2 or 78 cd/m2) had no effect on peripheral localization performance at any age. We also demonstrated that all subjects, regardless of age, had higher localization error rates to more peripherally located targets. In older subjects, error rates increased equally at all eccentricities; that is, there was an eccentricity independent increase in the number of target localization errors as a function of age. This finding does not support the interpretation of a selective constriction of the functional visual field in older subjects.

Purpose: To assess changes in measures of visual function in patients with retinitis pigmentosa (RP) over time. Methods: Patients with RP and visual acuity of 20/40 or better and central visual fields of 10° or larger were enrolled in a 9-year prospective study. The following measures of visual function were obtained annually over the follow-up period: visual acuity, Gold-mann visual fields (V4e target), focal electroretinograms, and hue discrimination. Results: Over the follow-up period, the averaged group data showed changes in all measures of visual function. The smallest amount of change occurred for visual acuity and hue discrimination, and the greatest amount of change occurred for visual field area. Examination of individual patient data over the follow-up period indicated that the rates of change varied among patients and that losses in function for one measure did not correlate well with losses on other measures. Conclusions: These results stress that although visual function deteriorated over time for this group of patients with RP, there were differences among our measures of visual function. Measures that primarily assess central retinal function change relatively slowly compared with measures that assess more peripheral retinal function.

The hypothesis that reductions in Snellen acuities in patients with retinitis pigmentosa are due solely to losses of photoreceptors was tested by measuring the effects of random losses of sampling elements on letter identification. Sampling element losses were mimicked by setting the luminance of randomly selected pixels equal to the luminance of the surround. The amount of pixel blanking ranged from 0 to 90%. Letters varying in retinal subtense from 5 to 17 min arc were presented for 500 msec. Although letter identification accuracy decreased with increasing pixel blanking for all letter sizes, performance remained relatively high even when a majority of the pixels was blanked. The data suggest that unless the loss of cone photoreceptors in greater than 80%, loss of sampling elements alone can not account for letter acuities poorer than20/40. In addition to loss of cone photoreceptors in patients with RP, there are histological reports of photoreceptor abnormalities and psychophysical studies of visual sensory deficits. It is conceivable that these alone, or in combination with losses of photoreceptors, could account for decreased visual acuity. In a series of experiments, stimulus parameters were manipulated in order to mimic the effects of some of these abnormalities and deficits and the effects on letter identification were examined. The results of these experiments demonstrated that sampling element loss interacts with sensory factors (e.g. luminance and contrast sensitivity) and perceptual factors (e.g. set size and letter orientation) to reduce letter identification accuracy. The implication of these results is that decreases in letter acuity observed in patients with retinitis pigmentosa cannot be attributedsolely to a random loss of sampling elements in the underlying retina, but may be due to the combination of photoreceptor degeneration and other sensory and perceptual factors.

To investigate the relative sensory and perceptual contributions to central visual function of patients with retinitis pigmentosa (RP), we tested symmetry discrimination using block patterns with varying types of symmetric organization. Eleven control subjects with normal vision and 11 patients with RP with 20/30 visual acuity or better, viewed patterns presented for 255 msec. The patterns differed in the type of symmetric organization and the subjects were required to identify the type. The control subjects performed significantly better (89.2%) than the patients (74.5%). Four hypotheses to account for these findings were tested and the results were as follows, (1) A reduction in pattern luminance did not change symmetry discrimination performance in the control subjects. (2) Large reductions in pattern contrast did not alter symmetry discrimination in the control subjects. (3) Reductions in stimulus duration, likewise, did not produce similar error patterns in the control subjects as those observed in the patients with RP. (4) Alterations in spatial sampling density did not completely account for the patients' deficits. None of the retinally based explanations alone was sufficient to account for our findings. Additionally, we suggest that alterations of sensory input may affect the perceptual encoding of the relationship among pattern elements.

The aim of this study was to determine the relative effects of age and compromised vision on driving-related skills and on-road accidents. A total of 107 subjects were tested. They represented four groups that varied in age and visual status, as follows: (1) a younger, normally sighted group; (2) an older, normally sighted group; (3) a younger, visually compromised group; and (4) an older, visually compromised group. Driving performance was assessed by self-reported and state-recorded accident frequency and by an evaluation of performance on an interactive driving simulator. The older groups had poorer driving-related skills, as measured with our interactive driving simulator, than had the younger groups, but they did not have significantly higher on-road accident rates than the younger groups. The older subjects and those with compromised vision had reduced risk-taking scores, as measured with a self-report questionnaire. In addition, all older drivers had increased eye movements and had slower simulator driving speeds, which suggests that behavioral compensation is made for visuocognitive/motor deficits. Regression analyses showed that compromised vision and visual field loss predicted real-world accidents in our study population.

To investigate the relationship between depression and quantitative measures of visual function, we recruited 18 subjects with central scotomas from macular degeneration who were enrolled in a reading rehabilitation program. Psychological batteries and reading assessments were administered prior to rehabilitation; reading assessments and a measure of adaptation to vision loss were administered following rehabilitation. We investigated relationships between reported levels of depressive symptoms and reading and adaptation outcome measures by using Pearson product moment correlation analysis. Results revealed a significant relationship between depression levels and reading acuity difference scores (r(16) = 0.54, p = 0.02) and changes in adaptation to vision loss levels (r(16) = 0.62, p = 0.01), suggesting that those who reported greater depressive symptoms did not respond as well functionally to reading rehabilitation but reported greater improvement in levels of adaptation to vision loss following rehabilitation. Future research should focus on defining standard methods to assess and remediate depression as part of the rehabilitation process.

Purpose To quantify the effects of three vision rehabilitation training approaches on improvements in reading performance. Methods Thirty subjects with AMD participated in the training portion of the study. The median age of the subjects was 79 years (range, 54-89 years). The three training modules were: Visual Awareness and Eccentric Viewing (module 1), Control of Reading Eye Movements (module 2), and Reading Practice with Sequential Presentation of Lexical Information (module 3). Subjects were trained for 6 weekly sessions on each module, and the order of training was counterbalanced. All subjects underwent four assessments: at baseline and at three 6-week intervals. Reading performance was measured before and after each training module. A separate group of 6 subjects was randomly assigned to a control condition in which there was no training. These subjects underwent repeated assessments separated by 6 weeks. Results Reading speeds decreased by an average of 8.4 words per minute (wpm) after training on module 1, increased by 27.3 wpm after module 2, and decreased by 9.8 wpm after module 3. Only the increase in reading speed after module 2 was significantly different from zero. Sentence reading speeds for the control group, who had no reading rehabilitation intervention, was essentially unchanged over the 18 weeks (0.96 ± 1.3 wpm). Conclusions A training curriculum that concentrates on eye movement control increased reading speed in subjects with AMD. This finding does not suggest that the other rehabilitation modules have no value; it suggests that they are simply not the most effective for reading rehabilitation.

The focal electroretinogram (FERG) was used to examine temporal frequency tuning at the outer retinal level in humans by measuring temporal modulation thresholds. Changes in FERG thresholds as a function of ambient light level were compared to temporal modulation thresholds obtained psychophysically using the same stimuli. At lower temporal frequencies, both FERG and psychophysical thresholds changed sensitivity proportional to the mean illuminance level. At higher illuminance levels, both threshold measures were relatively independent of illuminance. The comparison of the FERG to the behavioral data suggest that most of the adaptation-dependent changes in temporal sensitivity in humans occur at the level of the photoreceptor complex.

PURPOSE. To quantify the extent of visual function losses in patients with North Carolina Macular Dystrophy (NCMD) and to demonstrate the importance of accounting for eccentric fixation when making comparisons with normal data. METHODS. Five patients with NCMD who were from a single family were examined. Multifocal electroretinograms (mfERGs) and psychophysical assessments of acuity and luminance visual field sensitivities were measured throughout the central retina. Comparisons of responses from equivalent retinal areas were accomplished by shifting normal templates to be centered at the locus of fixation for each patient. RESULTS. Losses of psychophysically measured visual function in patients with NCMD extend to areas adjacent to the locations of visible lesions. The multifocal ERG amplitude was reduced only within the area of visible lesion. Multifocal ERG implicit times were delayed throughout the entire central retinal area assessed. CONCLUSIONS. ERG timing is a sensitive assay of retinal function, and our results indicate that NCMD has a widespread effect at the level of the mid and outer retina. The findings also demonstrated that it is necessary to account for fixation locus and to ensure that equivalent retinal areas are compared when testing patients with macular disease who have eccentric fixation. (Invest Ophthalmol Vis Sci. 2006;47:1703‐1709) DOI

PURPOSE. To determine whether training oculomotor control, without direct practice in reading sentences, could increase reading speed in patients with age-related macular degeneration (AMD). METHODS. Sixteen patients with AMD participated in the study (age range, 65– 87 years; mean, 77). The training program consisted of a series of exercises that were designed to allow the patients to practice eye movements. At the beginning of training, the subjects practiced small horizontal saccades in response to cognitively easy stimuli (e.g., dots). The training then progressed to practicing larger eye movements and then to practicing saccades with single letters, pairs of letters, and three-letter words. Reading of sentences was practiced in only one exercise, during the last session of the 8-week training. RESULTS. The difference between average reading speeds before and after training was 24.7 wpm (difference between medians, 17.9 wpm). The increase in speed was statistically significant (Wilcoxon signed rank test 124.0, P 0.001). There was no significant relationship between change in maximum reading speed and ETDRS (Early Treatment Diabetic Retinopathy Study) acuity (r 0.14, P 0.76) or between change in maximum reading speed and age (r 0.25, P 0.45). CONCLUSIONS. The results indicate that a training curriculum that concentrates on eye-movement control can increase reading speed in patients with AMD. This finding is especially interesting, because the training involved little direct practice in reading sentences but instead concentrated on having subjects practice control of eye positions and eye movements. (Invest Ophthalmol Vis Sci. 2005;46:2886 –2896) DOI

This study identifies clinical vision measures or retinal structural measures associated with the driving performance of diabetic retinopathy patients. Twenty-five licensed drivers with diabetic retinopathy (median age, 53 years; range, 34-72 years) completed clinical tests (visual acuity, letter contrast sensitivity, and Humphrey 30-2 visual fields) and structural examinations (retinal thickness analysis and fundus photograph grading of retinopathy and laser scarring). Driving performance was assessed with an interactive driving simulator and a driving history questionnaire. Increased retinal thickness was significantly correlated with a higher frequency of simulator accidents and near accidents. Laser scar grades significantly correlated with steeper brake-response slopes, increased brake-pressure standard deviation (SD), and longer response times. Subjects with focal laser scars had significantly higher average brake-pedal pressure and brake-pressure SD than subjects without focal laser scars. Retinal thickness and laser scarring correlated with driving simulator performance in subjects with diabetic retinopathy. Language: en

Multidimensional psychophysical and electrophysical maps of the central retina are essential for assessing the functioning of the diseased retina. In this study, grating acuity, contrast sensitivity, duration for letter identification, multifocal electroretinograms, and Humphrey visual field thresholds were measured at equivalent positions throughout the central 20 degrees. We found that the rates of sensitivity loss were not equivalent for all psychophysical measures. The rate of loss in the duration required for letter identification as a function of eccentricity was the steepest, followed by acuity and contrast sensitivity. The rate of loss in luminance sensitivity as measured in the Humphrey visual field was the shallowest. The pattern of losses also varied across meridians. Specifically, the rate of loss as a function of eccentricity was highest in the vertical meridian and lowest in the horizontal meridian. These maps and the correlations among measures as a function of retinal position serve as a baseline so that we can examine disease effects throughout the retina. In addition, the development of vision rehabilitation programs focused on eccentric viewing training should consider the differential sensitivities of the peripheral retina.

The purpose of this study was to investigate atypical multifocal ERG (mfERG) responses for patients with diseases that can affect the photoreceptors. MfERGS were obtained from seven patients with retinitis pigmentosa (RP), three with progressive cone dystrophy (CD) and eight with diabetic retinopathy (DR). Both first- and second-order kernel responses were analyzed. The amplitudes and implicit times of the first-order responses were compared to those obtained from age-similar controls. For the first slice of the second-order response, the root-mean-square (RMS) and the signal-to-noise ratio (SNR) of each response were calculated. Achromatic visual fields were also obtained from each subject. For the three groups of patients, first-order responses with relatively large amplitudes, broad-shaped waveforms and markedly increased implicit times had non-measurable second-order responses. These responses were associated with areas of decreased visual field sensitivity. As RP, CD and DR affect the outer retina, the results are consistent with damage to the outer plexiform layer rather than damage to the inner retina.

PURPOSE To determine the influence of age on local electroretinographic responses in humans. METHODS Multifocal electroretinograms (mfERGs) were obtained from 62 normally sighted subjects ranging in age from 21 to 81 years. A stimulus array of 103 scaled hexagons was used to measure electrical signals within a retinal area approximately 46 degrees in diameter. Commonly reported mfERG methods were used to quantify the responses: peak-to-peak amplitudes and implicit times, scalar product amplitude, and amplitude and time scales derived from the algorithm of Hood and Li, published in 1997. RESULTS Regression analysis showed significant linear relationships of amplitude and timing measures with age. The rates of losses were 10.5% per decade for peak-to-peak amplitude, 11.7% per decade for scalar product amplitude, and 9.5% per decade for a-scale. The rate of amplitude reduction was highest in the central 3 degrees. Age had less influence on implicit time measures. The rates of timing losses were 1.4% per decade for the N1 component and 1.0% per decade for both the P1 component and the t-scale measure. Using predicted interval ranges, the age was calculated at which 50% of the expected values would fall below the lower 95% prediction interval band of younger subjects. CONCLUSIONS The age-associated mfERG alterations are presented to emphasize the importance of appropriate normative data in interpretation of mfERGs.

To compare the patterns of local cone and rod system impairment in patients with progressive cone dystrophy (CD) using psychophysical and electrophysiological techniques.Local cone system function was assessed by measuring cone system thresholds (visual fields) and cone-mediated multifocal electroretinograms (mfERGs). Rod system function was assessed by measuring rod system thresholds (visual fields) and rod-mediated mfERGs. The results in a group of eight patients with CD were compared with those in an age-similar control group.All the patients had abnormal cone system visual field thresholds and cone-mediated mfERGs. Cone system psychophysical thresholds were elevated for targets presented within the central 10 degrees, but were within normal limits for targets at peripheral locations. Cone-mediated mfERG measures of amplitude scale and time scale were abnormal for most of the hexagons tested. Most of the rod-mediated psychophysical thresholds and mfERGs were within normal limits. Rod system losses tended to be patchy and scattered throughout the area tested.There was poor correspondence among local measures of cone and rod system losses in these patients with CD. The results suggest that the spatial pattern of cone system losses in this disease differs from the spatial pattern of rod system losses.

To determine the manner in which attention is distributed among numerous locations in the visual space, we used a multifocal recording technique that allowed simultaneous recordings of evoked cortical activity from 12 visual field areas out to 23.6°. We found that multifocal visual evoked potential (mfVEP) amplitude was larger when a region of visual space was attended than when it was not attended. The magnitude of this effect was inversely related to visual field eccentricity and there was no attention-related modulation of VEP amplitude for the most eccentric region. In addition, we found that mfVEP amplitudes in the regions contiguous to the attended region could also be larger, depending upon their spatial relationship to the attended region. Specifically, amplitudes in more central regions on the `meridian of attention' were larger when the subject attended anywhere along that meridian.

To evaluate the contrast response of the visual system in retinitis pigmentosa (RP) under conditions designed to emphasize the parvocellular (PC) and magnocellular (MC) pathways.Visual evoked potentials (VEPs) were measured in 10 patients with RP and in 10 age-equivalent control subjects with normal visual acuity and color vision, by using an array of isolated checks that were presented against a steady yellow background. The checks were modulated sinusoidally, either in isoluminant chromatic contrast (5.6 Hz), to favor the chromatic PC pathway, or in luminance contrast (5.6 and 11.2 Hz), to favor the MC pathway. Response amplitude and phase at the stimulus (fundamental) frequency were derived from Fourier analysis, and contrast response functions were fit with a Michaelis-Menten equation to derive R(max), the maximum response amplitude, and sigma, the contrast necessary to produce R(max)/2.In the control subjects, the mean amplitude function for chromatic modulation increased approximately linearly with increasing contrast, whereas the function for luminance modulation increased sharply at low contrasts and saturated at contrasts above approximately 30% for both temporal frequencies, as expected. The patients with RP showed primarily a reduction in R(max) with little change in sigma in all testing conditions. The reduction in R(max) was equivalent for chromatic modulation and luminance modulation at 5.6 Hz, but was substantially lower for luminance modulation at 11.2 Hz.Contrast processing was impaired within both the MC and PC pathways in these patients with RP, but the degree of impairment within the MC pathway depended on temporal frequency. These VEP results are in general agreement with recent psychophysical studies of contrast sensitivity losses in patients with RP, and further they characterize contrast processing deficits in these patients at suprathreshold levels.

PURPOSE. To determine the extent of rod and cone photoreceptor dysfunction in patients with cone dystrophy using psychophysical and electrophysiological tests. METHODS. Ten patients with cone dystrophy participated. Rod and cone system psychophysical thresholds were measured as a function of retinal eccentricity. Bright-flash full-field electroretinograms were obtained under dark-adapted (rod-mediated) and light-adapted (cone-mediated) conditions. The a-wave data were fitted with a model based on photopigment transduction to obtain values for log R max (maximum response) and log S (sensitivity). b-Wave parameters were also examined by fitting a nonlinear, saturating function (the Naka-Rushton equation) to the rod-mediated responses. Oscillatory potentials were measured to the cone-mediated high-intensity flashes. RESULTS. On average, the rod-mediated psychophysical thresholds were elevated by 0.5 log unit. These threshold elevations did not differ significantly with retinal eccentricity. In contrast, cone-mediated psychophysical thresholds were elevated up to 3.0 log units. Threshold elevation was greatest in the central retinal locations. For rod-mediated conditions, the a-wave R max parameter was significantly reduced in three patients; the a-wave log S parameter was within normal limits. The rod-mediated b-wave R max parameter was reduced in six patients; log k was abnormal in one patient. For cone-mediated conditions, the a-wave R max parameter was reduced in six patients and the a-wave log S parameter was reduced in two patients. The cone system oscillatory potentials were abnormal in nine patients. CONCLUSIONS. Patients with cone dystrophy show different patterns of psychophysical rod versus cone system sensitivity losses with retinal eccentricity. The full-field electrophysiological data indicate that most of the patients had abnormal cone photoreceptor function. Some patients also showed rod photoreceptor abnormalities. The rod system changes were smaller than the cone system changes.

Sensitivity losses in patients with retinitis pigmentosa (RP) have been attributed to a decrease in photopigment density, to a reduction in the number of photoreceptors, and also to a change in temporal response properties of the receptors. The sensitivity losses in patients with macular degeneration have also been attributed to a loss of photoreceptors. To test these explanations for sensitivity loss we obtained electrophysiological and psychophysical temporal modulation transfer functions (MTFs) on normal subjects in response to varying stimulus luminances and retinal loci. These stimulus manipulations did not duplicate the changes observed in the temporal MTFs of patients. The temporal response properties of the receptors were tested electrophysiologically by manipulating stimulus presentation interval. The results provided evidence for sensitivity losses in RP patients being due to alterations in the temporal response properties of the receptors.

To assess local retinal function in patients with retinitis pigmentosa (RP), multi-focal ERGs and local thresholds (static visual fields) were obtained on eight RP patients with visual acuities of 2025 or better. All eight patients showed multi-focal responses with normal timing within the central 5 deg. However, there were few responses with normal timing in the areas outside the central 7.5 deg, except in the case of the only patient with a 30 Hz full-field response with normal timing. Since full-field ERGs are dominated by responses from the periphery, this finding supplies a foundation for the commonly observed delays in the full-field cone ERGs of patients with RP. With respect to amplitude, only two patients showed multi-focal responses with near normal amplitudes anywhere in the field. The loss of amplitude at any point was not a good predictor of visual sensitivity in the Humphrey visual field. On the other hand, all areas with normal timing had near normal sensitivity. Timing changes appear to be an early indication of local retinal damage to the cone system. Nearly all areas with sensitivity losses greater than 0.5 log unit, and some areas with near normal sensitivity, showed significantly delayed multi-focal ERGs. Finally areas with extreme sensitivity loss show multi-focal responses with a wide range of amplitudes and implicit times across patients, suggesting different mechanisms of disease action in different patients.

Contributions to the multifocal electroretinogram (ERG) from the inner retina (i.e. ganglion and amacrine cells) were identified by recording from monkeys before and after intravitreal injections of n-methyl dl aspartate (NMdlA) and/or tetrodotoxin (TTX). Components similar in waveform to those removed by the drugs were identified in the human multifocal ERG if the stimulus contrast was set at 50% rather than the typically employed 100% contrast. These components were found to be missing or diminished in the records from some patients with glaucoma and diabetes, diseases which affect the inner retina.

Focal electroretinograms (FERG), pattern electroretinograms (PERG), and visual evoked potentials (VEP) were studied in a group of 30 aphakic patients with cystoid macular oedema (ACME). When compared with a control group of age-matched aphakics, 35% of patients were found to have abnormal FERG responses and 53%--over half of whom had normal FERG responses--showed abnormal PERG amplitudes. Although most of the patients had associated optic disc leakage, VEP latencies were normal in 26 out of 30. These results may explain the more severe visual loss seen in some ACME patients where the ophthalmologically visible retinal changes do not seem sufficient to explain such reduction in vision.

Purpose: The authors examined electrophysiologic and psychophysical measures of retinal function in patients infected with human immunodeficiency virus (HIV) at different stages of infection, including patients with cytomegalovirus retinitis (CMVR). Methods: All patients had complete ophthalmologic examinations. Rod-mediated psychophysical thresholds were measured using a modified two-color dark-adapted perimetry technique. Rod-dominated full field flash electroretinograms (ERGs) were obtained as a function of flash intensity, followed by cone-dominated ERGs. The 26 patients infected with HIV (26 eyes) were categorized into three groups. Six patients were infected with HIV but had not progressed to acquired immunodeficiency syndrome (AIDS), and 14 had AIDS. Six patients had CMVR with less than 10% of the retina involved. The data were compared with results from age-similar control subjects. Results: Psychophysical thresholds as a function of retinal eccentricity were elevated for each of the three stages of HIV infection. The group of patients with CMVR had the greatest amount of threshold elevation and threshold elevation increased with retinal eccentricity. In addition, all three patient groups had abnormal electroretinographic findings. Patients with CMVR were affected more severely on all measures than were the other HIV-infected groups. Conclusions: Results reveal that a diffuse functional retinal pathology exists in eyes with the funduscopic appearance of localized peripheral CMVR. Additionally, patients infected with HIV, including those without cotton wool spots, may have abnormal retinal function.

The field of electrodiagnostics is rapidly expanding. Improved computing power has expanded our ability to control stimuli and to analyze the biologic signals elicited by them. Similar trends are also affecting other areas ranging from biochemistry and genetics to imaging of the retina and brain. Natural, fertile areas of study are the overlap of these factors. Thus, we had invited papers by Aina Puce and Paul Sieving directed toward structure and function relationships in the cortex and retina. Additionally, we had several sessions related to imaging and electrophysiology.

Estuarine crabs usually show hatching periodicities closely synchronized with tidal, lunar, or solar day periodicities. To define their timing, we monitored hatching activity either directly (by observing females during hatching) or indirectly (by measuring larval densities during nocturnal ebbing tides). Larval densities in the Newport River, at a site (Beaufort) near the ocean, revealed two patterns. Intertidal species (Uca spp., Panopeus herbstii) showed highest densities twice monthly, during the spring tides. Subtidal species (Neopanope spp., three pinnotherids, the blue crab Callinectes sapidus) showed larval densities which, on the average, were similar during all ebbing tides. We speculate upon the selection pressures that may have shaped these differences and propose a hypothesis to explain why the patterns are adaptive. Fiddler crabs were used to determine when, in relation to high tide (HT), hatching occurred. Most larval release in the laboratory and under field conditions occurred within 1 h after HT. To determine what environmental cue might synchronize semimonthly hatching rhythms in fiddler crabs, we compared the timing of larval release at two local sites where tidal amplitude pattern was identical but HT time differed each night by an average of 1.92 h. The results suggested that fiddler crabs respond to tidal amplitude and not the time interval between HT and the onset of darkness.