Ophthalmoscopic evaluation of the optic nerve head.

PURPOSE. To investigate the relationship between ganglion cell losses and visual field defects caused by glaucoma. METHODS. Behavioral perimetry and histology data were obtained from 10 rhesus monkeys with unilateral experimental glaucoma that was induced by argon laser treatments to their trabecular meshwork. After significant visual field defects had developed, the retinas were collected for histologic analysis. The ganglion cells were counted by light microscopy in cresyl violet-stained retina sections, and the percentage of ganglion cell loss (treated to control eye counts) was compared with the depth of visual field defect (treated to control eye thresholds) at corresponding retinal and perimetry test locations. Sensitivity losses as a function of ganglion cell losses were analyzed for Goldmann III, white and Goldmann V, and short- and long-wavelength perimetry test stimuli. RESULTS. The relationship between the proportional losses of ganglion cells and visual sensitivity, measured with either white or colored stimuli, was nonlinear. With white stimuli, the visual sensitivity losses were relatively constant (approximately 6 dB) for ganglion cell losses of less than 30% to 50%, and then with greater amounts of cell loss the visual defects were more systematically related to ganglion cell loss (approximately 0.42 dB/percent cell loss). The forms of the neural-sensitivity relationships for visual defects measured with short- or long-wavelength perimetry stimuli were similar when the visual thresholds were normalized to compensate for differences in expected normal thresholds for white and colored perimetry stimuli. CONCLUSIONS. Current perimetry regimens with either white or monochromatic stimuli do not provide a useful estimate of ganglion cell loss until a substantial proportion have died. The variance in ganglion cell loss is large for mild defects that would be diagnostic of early glaucoma and for visual field locations near the fovea where sensitivity losses occur relatively late in the disease process. The neural-sensitivity relationships were essentially identical for both white and monochromatic test stimuli, and it therefore seems unlikely that the higher sensitivity for detecting glaucoma with monochromatic stimuli is based on the size-dependent susceptibility of ganglion cells to injury from glaucoma.

Ganglion cell losses underlying visual field defects from experimental glaucoma

Effect of Corneal Polarization Axis on Assessment of Retinal Nerve Fiber Layer Thickness by Scanning Laser Polarimetry

Objective To correlate macular thickness and retinal nerve fiber layer (RNFL) thickness in normal and glaucomatous eyes using optical coherence tomography. Methods Complete examination, automated achromatic perimetry, and optical coherence tomography of the peripapillary RNFL and macula were performed. Exclusion criteria were visual acuity of less than 20/40, diseases other than glaucoma, and unreliable automated achromatic perimetry. Macular thickness measurements were generated using 6 radial optical coherence tomographic scans (5.9 mm) centered on the fovea, and mean and quadrantic macular thickness values were calculated. Results Fifty-nine eyes of 59 patients (29 normal and 30 glaucomatous) were enrolled (mean ± SD age, 56.7 ± 20.3 years; range, 20-91 years). All eyes with glaucoma had associated visual field loss (mean ± SD mean defect, −8.4 ± 5.8 d B). Mean macular thickness was significantly associated with visual field mean defect ( R 2 = 0.47; P R 2 = 0.32; P R 2 = 0.38; P P = .005) than in the unaffected quadrant (286± 27 µm). Mean RNFL thickness in the affected quadrant (89 ± 53 µm) was significantly thinner ( P = .009) than in the unaffected quadrant (121 ± 39 µm). Main Outcome Measures Mean total and quadrantic macular and RNFL thickness measurements. Conclusions Macular thickness changes are well correlated with changes in visual function and RNFL structure in glaucoma and may be a surrogate indicator of retinal ganglion cell loss.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/414993/ECS20034.pdf

Shah In Shahrokni

Papers

Association Between Quantitative Nerve Fiber Layer Measurement and Visual Field Loss in Glaucoma