Faculty Bibliography

PURPOSE: To evaluate quantitatively the effects of tinted spectacle lenses on visual performance in individuals without visual pathology. METHODS: Twenty-five subjects were assessed by measuring contrast sensitivity with and without glare. Gray, brown, yellow, green, purple, and blue lens tints were evaluated. Measurements were repeated with each lens tint and with a clear lens, and the order was counterbalanced within and between subjects. Glare was induced with a modified brightness acuity tester. RESULTS: All subjects demonstrated an increase in contrast thresholds under glare conditions for all lens tints. However, purple and blue lens tints resulted in the least amount of contrast threshold increase; the yellow lens tint resulted in the largest contrast threshold increase. CONCLUSIONS: Purple and blue lens tints may improve contrast sensitivity in control subjects under glare conditions

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 logT=logT(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

OBJECTIVE: To test the hypothesis that the retinal pigment epithelial/photoreceptor complex is affected in patients with pigment dispersion syndrome and/or in patients with pigmentary glaucoma. METHODS: Electro-oculograms were recorded from patients with pigment dispersion syndrome, pigmentary glaucoma, ocular hypertension, and primary open-angle glaucoma and from control subjects. Electro-oculograms were recorded during 15 minutes of dark adaptation followed by 15 minutes of light adaptation. For each subject, dark-trough amplitudes, dark-trough latencies, light-peak amplitudes, light-peak latencies, and ratios of the light-peak amplitude to the dark-trough amplitude (Arden ratios) were calculated. RESULTS: A 1-way analysis of variance of the Arden ratios indicated significant differences among the groups of subjects. Results of a post hoc Newman-Keuls test revealed that the mean Arden ratios of patients with pigment dispersion syndrome and patients with pigmentary glaucoma were significantly lower than the mean ratios of the controls, the patients with primary open-angle glaucoma, and those with ocular hypertension. CONCLUSIONS: The results provide support for the hypothesis that the integrity of the retinal pigment epithelial/photoreceptor complex is affected in patients with pigment dispersion syndrome and in those with pigmentary glaucoma. Congenital and/or structural abnormalities of the retinal pigment epithelial/photoreceptor complex should be considered when models of the etiology of pigment dispersion syndrome are proposed

PURPOSE: To determine the correlation between the aesthetics of lens tints preferred for cosmesis and lens tints preferred for viewing. METHODS: Thirty-five subjects (mean age: 25; 49% male, 51% female) with no significant ocular pathology participated in the study. Median visual acuity was 20/20. Color vision testing was performed on each subject using Ishihara plates, and those with abnormal scores were excluded from the study. Subjects were shown nine pre-selected tinted lenses (50% transmittance) of variable wavelengths. These lenses were mounted on two separate color backgrounds, one white and the other approximating their skin tone. Subjects were asked to choose from each background which tinted lens they would most prefer to wear and which lens they would least prefer to wear. The subjects were then shown a series of eight pictures (four nature photographs and four paintings) with different dominant wavelengths. Subjects were asked to grade the aesthetic effect of a clear lens and each of the nine tinted lenses on the appearance of the pictures. Chromaticity coordinates were calculated for each lens and picture. RESULTS: The blue lens was the most frequently chosen preferred lens to wear, followed by green, purple, and gray. The least preferred lenses were yellow, brown, and pink. For viewing the nature photographs, the clear lens was preferred over any of the tinted lenses. For viewing the paintings, the purple lens was most preferred. The yellow lens was least preferred for both photographs and paintings. CONCLUSIONS: Younger individuals with no significant ocular pathology preferred viewing both nature photographs and paintings through tinted lenses that did not, or only slightly, altered the chromaticity of the image. Whereas a clear lens was favored over the tinted lenses for viewing the photographs, some tinted lenses (purple and pink) were preferred for viewing paintings. There was no correlation between the most favored lens tint chosen based purely on cosmesis and the most favored lens tint based on viewing preference. However, the least preferred lens tint for cosmesis and viewing was yellow

OBJECTIVE: Schizophrenia is associated with deficits in higher-order processing of visual information. This study evaluated the integrity of early visual processing in order to evaluate the overall pattern of visual dysfunction in schizophrenia. METHOD: Steady-state visual-evoked potential responses were recorded over the occipital cortex in patients with schizophrenia and in age- and sex-matched comparison volunteers. Visual-evoked potentials were obtained for stimuli composed of isolated squares that were modulated sinusoidally in luminance contrast, number of squares, or chromatic contrast in order to emphasize magnocellular or parvocellular visual pathway activity. RESULTS: Responses of patients to magnocellular-biased stimuli were significantly lower than those of comparison volunteers. These lower response levels were observed in conditions using both low luminance contrast and large squares that biased processing toward the magnocellular pathway. In contrast, responses to stimuli that biased processing toward the parvocellular pathway were not significantly different between schizophrenia patients and comparison volunteers. A significant interaction of group and stimulus type was observed in the condition using low luminance contrast. CONCLUSIONS: These findings suggest a dysfunction of lower-level visual pathways, which was more prominent for magnocellular than parvocellular biased stimuli. The magnocellular pathway helps in orienting toward salient stimuli. A magnocellular pathway deficit could contribute to higher-level visual cognitive deficits in schizophrenia

PURPOSE. To compare local cone and rod system function in patients with retinitis pigmentosa (RP) using electrophysiological and psychophysical techniques. METHODS. Cone-mediated multifocal electroretinograms (M-ERGs), cone system threshold visual fields, rod-mediated M-ERGs, and rod system threshold visual fields were measured in seven patients with RP. RESULTS. All the patients had normal cone system visual field thresholds and normal cone-mediated M-ERG implicit times within the central 5 degrees. Both cone-mediated responses were abnormal at some peripheral retinal locations. There were significant correlations among cone system amplitude, timing, and visual field loss. All the patients had some retinal areas where the rod-mediated M-ERG amplitudes were not measurable. In areas where they were measurable, these rod-mediated M-ERG responses were often within normal limits for amplitude and timing. In contrast to the cone system data, there were no significant relationships between rod-mediated M-ERG measures and rod system threshold elevations. The cone and rod system psychophysical thresholds showed regional correspondence; the amplitude-scale and time-scale measures of the M-ERG did not. CONCLUSIONS. The results indicate that there was better local correspondence between psychophysical and electrophysiological measures in the cone system than in the rod system in patients with RP. In addition, the psychophysical measures of cone and rod system function showed better correspondence than did the electrophysiological measures

PURPOSE: To assess the effects of focal photocoagulation on retinal function in the macular and perimacular areas in patients with diabetes who have clinically significant macular edema. METHODS: Eleven patients were assessed after focal laser treatment. Multifocal electroretinogram (ERG) and full-field ERG techniques were used to evaluate the effects of treatment on macular, paramacular, and peripheral retinal function. A modified visual field technique was used to obtain local threshold fields. The posttreatment results were compared with pretreatment results. Changes in local ERG response amplitudes and implicit times were calculated for each patient and presented as difference fields. The changes in local ERG responses were compared with the changes in local field sensitivity. RESULTS: After treatment, the results of the psychophysical tests suggested little or no change in visual function, but changes in retinal function were observed with the multifocal ERG technique. Local ERG responses showed increases in implicit time and decreases in amplitude, compared with pretreatment values. Timing was affected more than amplitude. CONCLUSIONS: The results suggest that focal treatment produces changes in retinal function, and these changes are not restricted to the treated macular area

PURPOSE: To evaluate the nature and extent of retinal dysfunction in the macular and surrounding areas that occurs in patients with diabetes with clinically significant macular edema (CSME). METHODS: Eleven patients were evaluated before focal laser treatment. Multifocal electroretinogram (ERG) and full-field ERG techniques were used to assess the effects of diabetic retinopathy and CSME on macular, paramacular, and peripheral retinal function. A modified visual field technique was used to obtain local threshold fields. The relationship between local sensitivity changes and local ERG changes was determined. RESULTS: Local ERG responses were significantly delayed and decreased in amplitude, and timing changes were observed in a larger area of the retina than amplitude changes. Visual field deficits were similarly widespread with marked sensitivity losses occurring in retinal areas with normal ERG amplitudes and in areas that appeared to be free of fundus abnormalities. Despite this similarity and the finding that retinal areas with elevated thresholds have timing delays, timing delays were not good predictors of the degree of threshold elevation. CONCLUSIONS: The results demonstrate the widespread nature of timing deficits and visual field deficits that are associated with CSME