Progressive Thinning of Retinal Nerve Fiber Layer and Ganglion Cell-Inner Plexiform Layer in Glaucoma Eyes with Disc Hemorrhage

Association between Glaucoma Progression in Macular Ganglion Cell Complex and Disc Hemorrhage: Differences between Superior and Inferior Hemiretinas

Disc hemorrhage (DH) is often associated with glaucoma progression. A vertically asymmetrical pattern is typical of glaucoma progression, but it remains unclear whether the association between DH and glaucoma progression differs between the superior and inferior hemiretinas. We compared the thickness changes of the macular ganglion cell complex (GCC) in the hemiretinas of normal-tension glaucoma patients with or without DH, as well as between hemiretinas positive and negative for DH, during five years. Both the superior and inferior hemiretinas in the DH-positive group had a more negative GCC thickness slope in association with more DH counts compared to those in the DH-negative group. Conversely, only the inferior hemiretina exhibited a significant relationship between GCC thickness slope and DH counts when hemiretinas positive and negative for DH in the DH-positive group were compared. In the superior hemifield, the slope of the total deviation changes in the DH-positive hemifield of the DH-positive group was more negative compared to that of the DH-negative group. The association between DH and glaucoma progression in the macular GCC may be stronger in the inferior hemiretina, suggesting that more attention should be paid to DH in the inferior disc area as a sign of glaucoma progression.

Retinal Glutamate Neurotransmission: From Physiology to Pathophysiological Mechanisms of Retinal Ganglion Cell Degeneration

Glutamate neurotransmission and metabolism are finely modulated by the retinal network, where the efficient processing of visual information is shaped by the differential distribution and composition of glutamate receptors and transporters. However, disturbances in glutamate homeostasis can result in glutamate excitotoxicity, a major initiating factor of common neurodegenerative diseases. Within the retina, glutamate excitotoxicity can impair visual transmission by initiating degeneration of neuronal populations, including retinal ganglion cells (RGCs). The vulnerability of RGCs is observed not just as a result of retinal diseases but has also been ascribed to other common neurodegenerative and peripheral diseases. In this review, we describe the vulnerability of RGCs to glutamate excitotoxicity and the contribution of different glutamate receptors and transporters to this. In particular, we focus on the N-methyl-d-aspartate (NMDA) receptor as the major effector of glutamate-induced mechanisms of neurodegeneration, including impairment of calcium homeostasis, changes in gene expression and signalling, and mitochondrial dysfunction, as well as the role of endoplasmic reticular stress. Due to recent developments in the search for modulators of NMDA receptor signalling, novel neuroprotective strategies may be on the horizon.

Rates of Circumpapillary Retinal Nerve Fiber Layer Thinning and Capillary Density Loss in Glaucomatous Eyes with Disc Hemorrhage

PURPOSE

To investigate longitudinal changes in rates of optic nerve head circumpapillary retinal nerve fiber layer (cpRNFL) thinning and vessel density loss in patients with primary open-angle glaucoma with or without a history of disc hemorrhage (DH).

DESIGN

Observational cohort.

METHODS

In this longitudinal study, 34 eyes with DH and 134 eyes without DH that had ≥1.5 years of follow-up and 3 optical coherence tomography and optical coherence tomography angiography follow-up scans were enrolled. A linear mixed-effects model was used to compare the rates of cpRNFL thinning and vessel density loss between DH and non-DH eyes.

RESULTS

Rates of whole image capillary density loss were faster in the DH group compared with the non-DH group (mean difference [95% confidence interval] -0.32% [-0.59% to -0.04%] per year; P = .027). Faster mean rates of vessel density loss were found in the inferotemporal, inferonasal, and nasal sectors in eyes with DH than without DH (P < .05). There was no statistically significant difference in the global rate of cpRNFL thinning between the 2 groups (P = .679). The mean rate of cpRNFL thinning was faster in the DH group compared with the non-DH group only in the inferotemporal sector (mean difference [95% confidence interval] -1.01 μm (-1.62 μm to -0.40 μm) per year; P = .001).

CONCLUSIONS

Mean rates of vessel density loss between DH and non-DH eyes were different not only in the affected area but also in the other regions. In contrast, a significant difference in cpRNFL thinning between the 2 groups was detected only in the inferotemporal sector. Disc hemorrhage is an independent predictor of faster vessel density loss in glaucoma suspects and patients with primary open-angle glaucoma.