Optical Coherence Tomography Study of Experimental Anterior Ischemic Optic Neuropathy and Histologic Confirmation

Abstract

This was a serial SD-OCT quantification of acute and chronic changes following experimental AION, which revealed changes in the GCC similar to that of human AION, but over a time frame of weeks rather than months.

Changes in macular layers in the early course of non-arteritic ischaemic optic neuropathy

“…Histopathological studies in rodent models of AION indicate that an initial phase of swelling of the GCIP on day 1 is followed by thinning of the GCIP by weeks 2 and 4 [18]. This thinning is accompanied by significant loss of RGC bodies.…”

“…In previous interventional studies, patients were enrolled and treatment given to them if presentation was up to 2 weeks [14,20,21]. Since macular changes are already demonstrable at baseline and RGC death is already present at 2 weeks [18], it would be critical to administer any putative treatment as early as possible (hours from onset) and whilst documenting the state of the macula. This would mean that we ought to consider AION as an acute emergency similar to other ischaemic events such as stroke or myocardial infarction.…”

Subretinal fluid is common in experimental non-arteritic anterior ischemic optic neuropathy

“…We used a mouse photochemical thrombosis model of NAION that we have previously described, 14,15 and we have performed this injury model in hundreds of adult mice. To induce optic nerve head ischemia, we injected rose bengal (1.25 mM in phosphate-buffered saline, 2 ml/kg animal weight) intravenously through the tail vein, then exposed the optic disc to 15 consecutive laser spots with 400-mm diameter, 50-mW power, and 1-s duration using a frequency-doubled 532 nm Nd:YAG laser (Pascal, OptiMedica, Sunnyvale, CA, USA).…”

“…This has been achieved in mice, rats, as well as primates. [10][11][12][13][14][15] Subretinal fluid has not been described in the animal models of NAION.…”

Severe, Early Axonal Degeneration Following Experimental Anterior Ischemic Optic Neuropathy

“…[9][10][11][12] Following ischemia, RGC axons and soma are lost, and both axonal and somatic layer thinning can be measured in AION patients and to a certain extent in animal model using optical coherence tomography (OCT). [13][14][15][16][17] Many have used a laser-assisted photochemical thrombosis model to study axonal and somatic changes in RGCs after AION. [17][18][19][20][21][22][23] One day after AION induction, there is prominent swelling of the anterior optic nerve and abnormality of the visual evoked potential, indicating impaired axonal transport and blockade of signal transduction in the optic nerve.…”