The relationship between macular cell layer thickness and visual function in different stages of glaucoma.

PURPOSE: To determine whether there were differences in the structure-function relationship between early and advanced glaucoma, and study the association between thickness of discrete macular cell layers, the thickness of the retinal nerve fiber layer, and visual field sensitivity. METHODS: In all, 71 eyes of 50 subjects (28 glaucoma patients and 22 normal control subjects) were included. Thickness of macular retinal nerve fiber layer (mRNFL), macular inner retinal layer (mIRL), and macular outer retinal layer (mORL) were measured from Stratus optical coherence tomography macular scans, using our previously published segmentation algorithm. Visual sensitivity loss was determined by mean deviation (MD) using Humphrey Visual Field Analyzer. The mean thickness for each layer from the normal control subjects, early, and advanced glaucoma groups was compared. In addition, a mixed model analysis was used to explore the relationship between structure-function, allowing for possible interaction with glaucoma stage. RESULTS: The mean mRNFL thickness in early and advanced glaucoma patients was significantly less than measurements in normal subjects (P<0.01). The mean mIRL thickness in advanced glaucoma was significantly less than normal subjects (P=0.04). The mean mORL thickness in early and advanced glaucoma was not statistically significant different from that of normal subjects (P>0.8). There was no statistically significant difference in macular structure-function relationship between the two glaucoma groups (P>0.05). Mean mIRL thickness was significantly associated with MD (P=0.04). CONCLUSION: There was no significant difference in macular structure-function relationship between early and advanced glaucoma groups. Combined data from both glaucoma groups indicated that mIRL thickness was associated with visual sensitivity loss.

Lateral spread of adaptation as measured with the multifocal electroretinogram.

We examined whether lateral spread of adaptation can be observed in the electroretinogram in humans. Specifically, we tested whether the luminance level of a surrounding, nonmodulated annulus affects the multifocal electroretinogram (ERG) response of a modulated central area. Multifocal electroretinograms were recorded in response to an array of 37 unscaled hexagons subtending a retinal area of 38 deg x 35 deg. Responses were recorded in six control subjects. In the first series of experiments, only the center hexagon was modulated, while the surrounding 36 hexagons were held constant at either 0.45, 172, or 340 cd/m2. In a subsequent series of control experiments, modulation depth of the center hexagon was varied and the proximity of the surrounding hexagon systematically altered. For the center-modulated condition, response amplitude and implicit time for the first-order kernel response significantly decreased as a function of increasing surround luminance. Control experiments demonstrated that the effect of the surround illumination was not due to scattered light but was influenced by the proximity of the surrounding annulus. These results demonstrate that lateral adaptation influences can be measured using the multifocal ERG.