The purpose of this study was to determine what contributions are made to the rat fullfield electroretinogram (ERG) by ganglion cells (GCs). To that end, the ERG was assessed longitudinally following optic nerve transection (ONTx). Additional studies were conducted using intravitreal injections of pharmacologically active substances. The ERG was recorded simultaneously from both eyes of anaesthetized adult Brown-Norway rats ( (1) both pSTR and nSTR components in the rat depend directly upon intact GC responses, and that amacrine cell contributions to these components are relatively small; (2) scotopic ERG response components to brighter flashes receive little influence from GCs; (3) the rat photopic ERG also reflects GC signals and may serve as an additional useful test of GC function; (4) TTX had dramatic effects on the rat photopic ERG that were not attributable to GC currents, but rather to voltage-gated sodium currents in amacrine or interplexiform cells; (5) a small residual negative STR persisted after ONTx that was likely to be generated by graded responses of third-order retinal cells, most likely amacrine cells.

Longitudinal SDOCT imaging can detect deep ONH changes in EG eyes, the earliest of which are present at the onset of HRT-detected ONH surface height depression. These parameters represent realistic targets for SDOCT detection of glaucomatous progression in human subjects.

Purpose-To understand better the influence of retinal blood vessels (BVs) on the interindividual variation in the retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT).Subjects and Methods-RNFL thickness profiles were measured by OCT in 16 control individuals and 16 patients. The patients had advanced glaucoma defined by abnormal disc appearance, abnormal visual fields, and a mean visual field deviation worse than − 10 dB.Results-In general, the OCT RNFL thickness profiles showed 4 local maxima, with the peak amplitudes in the superior and inferior regions occurring in the temporal (peripapillary) disc region. There was considerable variability among individuals in the location of these maxima. However, the 4 maxima typically fell on, or near, a major BV with the temporal and inferior peaks nearly always associated with the main temporal branches of the superior and inferior veins and arteries. In the patients' hemifields with severe loss (mean visual field deviation worse than − 20 dB), the signals associated with the major BVs were in the order of 100 to 150 µm.Conclusions-The variation in the local peaks of the RNFL profiles of controls correlates well with the location of the main temporal branches of the superior and inferior veins and arteries. This correspondence is, in part, due to a direct BV contribution to the shape of the OCT RNFL and, in part, due to the fact that BVs develop along the densest regions of axons. Although the overall BV contribution was estimated to be relatively modest, roughly 13% of the total peripapillary RNFL thickness in controls, their contribution represents a substantial portion locally and increases in importance with disease progression.

Purpose To test whether the minimum rim area assessed by spectral domain optical coherence tomography (SD-OCT), based on the shortest distance from Bruch's Membrane Opening (BMO) to the inner limiting membrane, corresponds more closely to retinal nerve fiber layer (RNFL) thickness and visual field mean deviation (MD) than current rim measures in early glaucoma. Design Prospective cross-sectional study. Methods 221 participants with non-endstage glaucoma or high-risk ocular hypertension performed standard automated perimetry, and received SD-OCT and confocal scanning laser ophthalmoscopy (CSLO) scans, on the same day. Rim area measured by CSLO was compared with three SD-OCT rim measures from radial B-scans: horizontal rim area between BMO and ILM within the BMO plane; mean minimum rim width (BMO-MRW); and minimum rim area (BMO-MRA) optimized within sectors and then summed. Correlations between these measures and either MD from perimetry or RNFL thickness from SD-OCT were compared using Steiger's test. Results RNFL thickness was better correlated with BMO-MRA (r=0.676) or BMO-MRW (r=0.680) than with either CSLO Rim Area (r=0.330, p<0.001) or Horizontal Rim Area (r=0.482, p<0.001). MD was better correlated with BMO-MRA (r=0.534) or BMO-MRW (r=0.546) than with either CSLO Rim Area (r=0.321, p<0.001) or Horizontal Rim Area (0.403, p<0.001). The correlation between MD and RNFL thickness was r=0.646. Conclusions Minimum rim measurements from SD-OCT are significantly better correlated to both RNFL thickness and MD than rim measurements within the BMO plane, or based on the clinical disc margin. They provide new structural parameters for both diagnostic and research purposes in glaucoma.

During acute IOP elevation, functional changes progress from the proximal to the distal retina. Alterations in ganglion-cell-related ERG potentials occurred at IOPs (30-50 mmHg) commonly observed in rat experimental glaucoma models. Nonspecific functional changes were observed at acute IOP above 50 mmHg, suggesting that IOP should be maintained below this level in experimental glaucoma models if selective ganglion cell injury is to be sought. Repeated IOP spikes above this level may cause permanent, nonspecific damage, perhaps via ischemic mechanisms. Thus, IOP should be monitored frequently in these models.