Abstract
Purpose :
Transient sub-ischemic intraocular pressure (IOP) spikes are likely to occur in a number of secondary glaucomas and after intravitreal injections. However, the impact of these IOP spikes on the physiology of individual retinal ganglion cells (RGCs) is poorly understood. Here, we explore how acute IOP spikes in mice affect RGC physiology both immediately after the spike and following 1 or 7 days of recovery.
Methods :
Acute IOP elevation was achieved in 12-week old wild type C57BL6J mice of both genders by injecting viscoelastic into the anterior chamber (van der Heijden, et al., 2016). IOP was measured immediately after the viscoelastic injection (d0) and after 1 (d1) and 7 days (d7) of recovery. Mice were dark adapted for at least 2 hours at d0, d1, or d7, after which retinas were collected and mounted on a 60-electrode multielectrode array (MEA) for electrophysiology. The identification of RGCs and characterization of their receptive fields (RFs) was performed as described (Tao, et al., 2019). Spatial and temporal RF characteristics were assessed under photopic conditions and compared among eyes from all three time points.
Results :
The average IOP after acute elevation was 49.8±1.9 mmHg. In all injected eyes that were not immediately used for MEA testing, IOP returned to normal (8.6±0.4 mmHg) by d1 and remained normal thereafter. 137, 87 and 82 RGCs at d0, d1, and d7, respectively, were included in the study. RGC spontaneous firing rate was decreased at d0 and d1, but returned to normal at d7. Photopic center RF size was decreased only at d0. The center RF peak time was increased at all time points. Photopic surround RF peak time and surround polarity also showed a range of effects across time points.
Conclusions :
Acute IOP spikes are a common part of clinical practice but have uncertain impact on RGC physiology. When exposed to a transient sub-ischemic IOP spike, mouse RGCs display marked changes in both center and surround RF properties, of which only some recover. These previously unappreciated findings suggest that IOP spikes may cause unrecognized pathology to RGCs which should be accounted for in clinical practice and which are deserving of further study.
This is a 2020 ARVO Annual Meeting abstract.