Reproducibility of activation maps for longitudinal studies of visual function by functional magnetic resonance imaging.

PURPOSE: To test the intra- and intersubject reproducibility of brain activation patterns that underlie visually guided saccades and word recognition in normally sighted subjects and patients with macular degeneration using functional magnetic resonance imaging (fMRI). METHODS: Ten normally sighted subjects and five patients with macular degeneration were asked to perform two visually guided saccade tasks and two word-recognition tasks during fMRI with behavioral monitoring. The fMRI measurements were repeated three times at intervals of at least 4 weeks between sessions. The intrasubject reproducibility of the brain activation patterns was examined in a model-independent manner by comparing the distributions of activation across the frontal, parietal, temporal, and occipital brain lobes using Intraclass Correlation Coefficients (ICCs). Intersubject reproducibility was examined by repeated-measure ANOVA. Results. Control subjects showed overall higher intrasubject reproducibility of brain activation patterns (75% ICCs > 0.5) than that of patients with macular degeneration (56% ICCs > 0.5). The intrasubject reproducibility for the patients improved when the target location was fixed, as in the word-recognition tasks (75% ICCs > 0.5), compared with the visually saccade tasks (37% ICCs > 0.5). Intersubject variability of brain activation patterns was strikingly high for both the control and patient groups. CONCLUSIONS: The fMRI method can serve as a reliable within-subjects measure of brain activation that has potential for measuring longitudinal changes in brain networks associated with rehabilitation training. Striking intersubject variability reflected at the level of lobes of the brain among control subjects with similar behavioral performance, suggests individual analysis is necessary when implementing longitudinal brain activation studies.

Reading rehabilitation of individuals with AMD: relative effectiveness of training approaches.

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.

Effect of depression on actual and perceived effects of reading rehabilitation for people with central vision loss.

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.

An FMRI study of word-level recognition and processing in patients with age-related macular degeneration.

PURPOSE: To compare the cortical networks that underlie word recognition and processing in patients with age-related macular degeneration (AMD) with those of normally sighted control subjects using functional magnetic resonance imaging (fMRI). METHODS: Six patients with bilateral geographic atrophy who were using an eccentrically located preferred retinal location were recruited. Six younger and six older control subjects were also recruited. Patients and control subjects were asked to perform a three-letter (3Let) and a six-letter (6Let) word recognition task during fMRI on a 3.0-Tesla MRI scanner. The fMRI tasks were two-condition, blocked-design paradigms in which central fixation was alternated with a word recognition task requiring a forced, two-choice reaction time living/nonliving judgment. RESULTS: When contrasted with controls, patients showed increased brain activation in a widespread cortical network that included regions identified as the frontal eye fields, both superior and inferior parietal lobules, and regions within the prefrontal cortex. Peak activation within these prefrontal regions was correlated with increased accuracy (r = 0.875, P = 0.024; r = 0.848, P = 0.033) and decreased reaction times (r = -0.861, P = 0.028; r = -0.842, P = 0.036) for the 3Let task within the group of patients. Correlations between peak activity and behavioral performance were also found in both the right (-0.818, P = 0.047) and left (r = -0.839, P = 0.037) superior parietal lobules for the 3Let task. Similar relationships were found for the 6Let task. CONCLUSIONS: Patients with AMD demonstrate increased prefrontal and parietal activation compared with controls. The authors posit that these increases reflect increased top-down involvement in basic word recognition to compensate for decreased sensory function.

Macular structure and vision of patients with macular heterotopia secondary to retinopathy of prematurity.

PURPOSE: To examine if vision in subjects with macular heterotopia (MH) secondary to retinopathy of prematurity (ROP) is related to anatomical macular structure. METHODS: Six subjects with MH who were between 18 years and 65 years of age and three age-matched subjects with normal vision were recruited for the study. Vision and macular structure of the better eye of the subjects with MH and the dominant eye of age-matched subjects with normal vision were assessed. High contrast visual acuity and contrast sensitivity were measured using Early Treatment of Diabetic Retinopathy Study and Pelli-Robson charts, respectively. The Micro Perimeter (Nidek Technologies MP-1) was used to assess macular sensitivity and fixation stability. Using optical coherence tomography, macular thickness and relative retinal thickness at fixation were measured. RESULTS: Subjects with MH had significantly reduced visual acuity and macular sensitivity compared with age-matched subjects with normal vision. In comparison with their age-matched counterparts, subjects with MH had significantly increased macular thickness and increased relative retinal thickness at fixation. A normal foveal architecture was absent in three subjects with MH (50%). CONCLUSION: Patients with MH secondary to ROP have increased macular thickness and reduced vision.

An FMRI study of saccadic and smooth-pursuit eye movement control in patients with age-related macular degeneration.

PURPOSE: To compare the cortical networks that underlie oculomotor function in patients with age-related macular degeneration (AMD) with those in normally sighted control subjects, using functional magnetic resonance imaging (fMRI). METHODS: Six patients with bilateral geographic retinal atrophy due to AMD (age range, 55-83 years) were recruited for the study. The visual acuities of the patients ranged from 20/76 (0.58 logMAR) to 20/360 (1.26 logMAR). An additional six younger (age range, 22-31 years) and six older (age range, 54-78 years) normally sighted individuals were recruited as control subjects. fMRI data were acquired on a 3.0-Tesla, scanner while subjects performed visually guided saccade (VGS) and smooth-pursuit (SmP) tasks. RESULTS: Contrasts between VGS and fixation on a stationary target identified a network of activation that included the frontal eye fields (FEFs), supplementary eye fields (SMA/SEFs), prefrontal cortex (PFC), intraparietal sulci (IPS), and the areas of the visual cortex (MT/V5, V2/V3, and V1) in control subjects and patients. A similar network was identified for comparisons between SmP and periods of fixation. Marked variability was observed in the performance of both tasks across all patients. For both tasks, the patients generally showed increased PFC and IPS activation, with decreased activation in visual cortex compared with the control subjects. The patients showed significantly increased activation of the FEFs and SMA/SEFs in the SmP task, compared with the control subjects. CONCLUSIONS: These data suggest that performance of both eye movement tasks required greater involvement of the cortical regions generally implicated in attention and effort in patients with AMD.

Detection of mosaic retinal dysfunction in choroideremia carriers electroretinographic and psychophysical testing.

PURPOSE: To test whether choroideremia carriers have a mosaic pattern of retinal dysfunction, as noted in carriers of X-linked recessive retinitis pigmentosa and X-linked retinoschisis. DESIGN: Prospective observational case series. PARTICIPANTS: Seven obligate choroideremia carriers (age range, 18-72) with visual acuity (VA) of 20/25 or better were recruited into the study. METHODS: The carriers underwent VA testing (Snellen chart), ophthalmic examination, Humphrey visual field (VF), and multifocal electroretinographic testing. The amplitude and implicit time scales were measured by the algorithm of Hood and Li. The amplitude measures (a scales) and implicit time measures (t scales) were reported abnormal when they were >2 standard deviations above the mean of age-similar normally sighted control subjects. MAIN OUTCOME MEASURES: Mapping of local 103 electroretinographic response amplitudes and implicit times. RESULTS: Only 1 of the 7 carriers showed abnormal Humphrey VF thresholds, whereas 6 of the 7 carriers showed a mosaic pattern of retinal dysfunction measured by multifocal electroretinographic testing. All 6 carriers showed statistically significant implicit time delays, whereas 4 carriers showed statistically significant amplitude reductions and implicit time delays (P<0.05 to P<0.0006). One carrier with a normal-appearing macula and normal Humphrey VF showed a cluster of statistically significant implicit time delays within the macula (P<0.05 to P<0.0006). The overall extent of local electroretinographic abnormalities corresponded to the severity of ophthalmoscopically apparent pigmentary changes. The one carrier with mild threshold elevation on Humphrey VF testing showed the most ophthalmoscopically apparent extensive fundus pigmentary changes. CONCLUSIONS: We demonstrated a mosaic pattern of retinal cone dysfunction in carriers of choroideremia. Our findings are consistent with the Lyon hypothesis of random X-chromosome inactivation. Multifocal electroretinographic testing is potentially sensitive to detect local retinal dysfunction in choroideremia carriers even in those with a normal-appearing macula and good VA.

Retinal dysfunction in carriers of bardet-biedl syndrome.

PURPOSE: To determine whether retinal dysfunction in obligate carriers of the Bardet-Biedl syndrome (BBS) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). METHODS: Six obligate carriers of the BBS were examined for the study. Examination of each carrier included an ocular examination and mfERG testing of one eye. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40 degrees 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 within a central 40 degrees area with the mfERG showed regions of reduced mfERG amplitudes in three of six carriers. Implicit time measurements in the 6 carriers were all normal except for those locations associated with abnormal amplitude reductions in 3 of the carriers. When present, retinal dysfunction was evident in the presence of a normal-appearing fundus. CONCLUSIONS: Multifocal ERG testing can demonstrate areas of retinal dysfunction in carriers of the BBS. This test may therefore be useful for identifying some heterozygous carriers of this disease.

Multifocal ERG findings in carriers of X-linked retinoschisis.

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 degrees 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 degrees 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.

Measuring outcomes of vision rehabilitation with the Veterans Affairs Low Vision Visual Functioning Questionnaire.

PURPOSE: To evaluate the sensitivity to change, in patients who undergo vision rehabilitation, of the Veteran Affairs (VA) Low Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have in performing daily activities and to evaluate vision rehabilitation outcomes. METHODS: Before and after rehabilitation, the VA LV VFQ-48 was administered by telephone interview to subjects from five sites in the VA and private sector. Visual acuity of these subjects ranged from near normal to total blindness. RESULTS: The VA LV VFQ exhibited significant differential item functioning (DIF) for 7 of 48 items (two mobility tasks, four reading tasks, and one distance-vision task). However, the DIF was small relative to baseline changes in item difficulty for all items. Therefore, the data were reanalyzed with the constraint that item difficulties do not change with rehabilitation, which assigns all changes to the person measure. Subjects in the inpatient Blind Rehabilitation Center (BRC) program showed the largest changes in person measures after vision rehabilitation (effect size = 1.9; t-test P < 0.0001). The subjects in the outpatient programs exhibited smaller changes in person measures after rehabilitation (effect size = 0.29; t-test P < 0.01). There was no significant change in person measures for the control group (test-retest before rehabilitation). CONCLUSIONS: In addition to being a valid and reliable measure of visual ability, the VA LV VFQ-48 is a sensitive measure of changes that occur in visual ability as a result of vision rehabilitation. Patients' self-reports of the difficulty they experience performing daily activities measured with this instrument can be used to compute a single number, the person measure that can serve as an outcome measure in clinical studies. The VA LV VFQ-48 can be used to compare programs that offer different levels of intervention and serve patients across the continuum of vision loss.

Perifoveal function in patients with North Carolina macular dystrophy: the importance of accounting for fixation locus.

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.

Assessing responses of the macula in patients with macular holes using a new system measuring localized visual acuity and the mfERG.

PURPOSE: To evaluate acuity and multifocal electroretinogram (mfERG) responses from the macula in affected and unaffected fellow eyes of patients with macular holes. METHODS: We tested 10 eyes with macular hole and 10 fellow eyes from 11 patients. We measured local visual acuity thresholds at 27 discrete locations within 21 degrees diameter using the Functional Fundus Imaging System (FFIS), a psychophysical system that measures visual acuity as a function of visual field location, and local ERG responses within 45 degrees diameter using the mfERG. RESULTS: In the affected eyes, the mean FFIS visual acuity thresholds were significantly elevated within the central 21 degrees diameter area, compared to a group of control eyes. No significant differences were found between the acuities of the fellow eyes compared to those of the control group. The amplitudes of the first positive peak of the mfERG were reduced in the central 7.8 degrees in affected eyes. In the central 2 degrees , 4 out of 10 affected eyes showed non-measurable ERG signals. The remaining six eyes showed significantly reduced mean amplitudes, but not delayed implicit times, when compared to the control group. For the fellow eyes, the mean amplitudes of the mfERG and implicit times did not differ from the means of the control eyes. CONCLUSIONS: Both local psychophysical and electrophysiological testing demonstrated retinal dysfunction extending beyond the site of the macular holes in some patients (three of the patients had central mfERG amplitudes falling within the normal range).

The effect of occlusive patching on visually-directed tasks.

PURPOSE: Occlusive patching is used to treat a variety of ocular conditions. A paucity of literature exists regarding the effects of occlusion on functional tasks and driving performance. We investigated the immediate effects of occlusive patching on a variety of visually dependent tasks as well as driving performance on a simulator. METHODS: Thirty normally sighted subjects were examined in a prospective randomized manner. All subjects underwent a complete medical history and eye examination. All subjects performed a variety of near tasks and drove a driving simulator with and without patching. The tasks included traditional clinical depth tests, tests of visual memory, scanning, and tracking, and gross and fine-motor abilities. All subjects filled out a questionnaire relating to their perception of the effects of patching on functional tasks and driving ability. RESULTS: Visual memory, scanning, tracking, and perceptual constancy were unaffected by patching. However, there were significant differences between the patched and unpatched conditions for four of five of the three-dimensional visual coordination tasks. Eight of 19 (42%) of the fine-motor tasks and 4 of 9 gross-motor tasks (44%) showed significant differences between the patched and unpatched conditions. A greater frequency of out of lane events and more abrupt braking profiles were seen when subjects drove monocularly rather than binocularly. CONCLUSIONS: Sudden occlusion immediately changes perceptual ability by decreasing visual field and eliminating stereoacuity. This has important implications for the performance of everyday tasks.

Eye-movement training for reading in patients with age-related macular degeneration.

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.

Comprehensive functional vision assessment of patients with North Carolina macular dystrophy (MCDR1).

PURPOSE: Previous studies indicated abnormal development of fixation toward the optic nerve head in patients with the inherited retinal disease North Carolina macular dystrophy (NCMD). The implication of this development on functional vision and structural characteristics has not been described. METHODS: The anatomical characteristics of five NCMD-affected individuals were assessed by measuring the retinal thickness of the macula using optical coherence tomography. The underlying physiologic health of the retina was assessed using the multifocal ERG. Psychophysical assessment of remaining vision in the affected areas was done with a new microperimetry system that measures functional visual acuity at 27 discrete locations and the Humphrey visual field analyzer. RESULTS: All patients had better areas of visual sensitivity toward the nasal macula. Follow-up examination showed no changes in the clinical appearance of the retina. Visual acuities ranged from -0.10 logMAR (Snellen equivalent, approximately 20/16) to 0.50 logMAR (Snellen equivalent, approximately 20/63) in the better eye. No significant changes in visual acuity were found over time. Local multifocal electroretinogram deficits were found in all patients. Patients with grade 2 or 3 disease had large patches of decreased amplitudes and delayed implicit times. Results of the anatomical, electrophysiological, and psychophysical tests were consistent. CONCLUSION: The electrophysiological and psychophysical deficits found in patients with more severe disease were consistent with an abnormal development of fixation from the anatomical fovea toward the optic nerve head with the placement of the lesion temporal to fixation (into the nasal visual field).

Driving performance of glaucoma patients correlates with peripheral visual field loss.

PURPOSE: To identify clinical vision measures that are associated with the driving performance of glaucoma patients who have visual field loss and visual acuity better than 20/100 and to compare the driving performance of glaucoma patients with the driving performance of a group of age- and sex-equivalent individuals without eye disease. PATIENTS: Forty patients with glaucoma and 17 normally sighted control subjects participated in this study. METHODS: Clinical vision data, consisting of visual acuity, letter contrast sensitivity, and visual fields, were collected. Driving performance was assessed by (1) an interactive driving simulator that measured 7 indices of performance (including number of accidents) and (2) the self-reported accident involvement for the past 5 years. MAIN OUTCOME MEASURES: Driving simulator performance and real-world, self-reported accident involvement. RESULTS: The number of accidents as measured on the driving simulator in the glaucoma group was significantly correlated with three Goldmann visual field measures: combined horizontal extent (rho = -0.47, P = 0.01), total horizontal extent (rho = -0.49, P = 0.007), and total peripheral extent (rho = -0.55, P = 0.002). There were no statistically significant correlations between the driving performance of the glaucoma group and the visual acuity or contrast sensitivity measures. When compared with the control group, a significantly greater proportion of the glaucoma group reported having at least one real-world accident within the past 5 years (Fisher exact test, P = 0.005). CONCLUSIONS: Visual field reduced to less than 100 degrees of horizontal extent may place patients with peripheral field loss at greater accident risk. A higher incidence of real-world and simulator accidents was found for the group with glaucoma.

Use of prisms for navigation and driving in hemianopic patients.

PURPOSE: (1) To compare the outcomes of orientation and mobility and driving training with Fresnel prisms and the Gottlieb Visual Field Awareness System for patients with homonymous hemianopsia, and (2) To determine whether the patients continue to use the optical enhancement devices at a 2-year follow-up point. METHODS: Patients with homonymous hemianopsia were provided with a rehabilitation program where they were fitted with prism lenses and trained to use them for navigation and driving. Telephone interviews were used to obtain information about device usage 2 years following the completion of the training program. RESULTS: Patients' performance was compared with a test-retest criterion in the visual skills areas of recognition, mobility, peripheral detection, scanning, tracking, and visual memory. Patients with hemianopic loss showed improvements in all of the visual skills categories, ranging from the highest improvements of 26% of tasks improved in the mobility category to 13% in the recognition category. The majority of the hemianopic patients reported using the devices at the 2-year follow-up interview. CONCLUSIONS: The patients with homonymous hemianopsia showed improvements in visual functioning using prism lenses, although these improvements were smaller than those found in previous studies with central or bilateral peripheral vision loss groups who were trained to use other optical enhancement devices for navigation and driving using a similar curriculum. However, given the evidence of increased risk of accidents for patients with peripheral vision loss, the safety of peripheral enhancement devices for driving must be thoroughly evaluated before their impact on public safety is known.

Use of Rasch person-item map in exploratory data analysis: a clinical perspective.

The National Institutes of Health (NIH) includes visual impairment in the 10 most prevalent causes of disability in America. As rehabilitation programs have the potential to restore independence and improve the quality of life for affected persons, NIH research priorities include evaluating their effectiveness. This paper demonstrates a clinical perspective on the use of the Rasch person-item map to evaluate the range and precision of a new vision function questionnaire in early analysis (prior to full sample). A self-report questionnaire was developed to measure the difficulty that persons with different levels of vision loss have performing daily activities. This 48-item Veterans Affairs Low-Vision Visual Functioning Questionnaire (VA LV VFQ-48) was administered to 117 low-vision patients. Preliminary analysis indicates that the questionnaire items are applicable to persons of differing abilities. The Rasch person-item map demonstrates that the field-test version of the VA LV VFQ-48 has good range and is well centered with respect to the person measure distribution. Construct validity and reliability are also demonstrated.

Relationship of retinal structural and clinical vision parameters to driving performance of diabetic retinopathy patients.

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.

Multidimensional visual field maps: relationships among local psychophysical and local electrophysiological measures.

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.