Early detection of retinal alteration by visible and near-infrared optical co-herence tomography (vnOCT) in a dexamethasone-induced ocular hypertension mouse model

Abstract

Purpose: To apply a novel visible and near-infrared optical coherence tomography (vnOCT) in the dexamethasone-induced ocular hypertension mouse model, and test the capability of four optical markers, peripapillary retinal nerve fiber layer (RNFL) thickness, total retinal blood flow, VN ratio and hemoglobin oxygen saturation (sO2), in detecting retinal ganglion cell (RGC) damage in association with ocular hypertension.Methods: Twelve mice (C57BL/6J) were separated into a control (n=6) and a dexamethasone group (n=6) receiving twice daily saline or dexamethasone eye drops, respectively, for 7 weeks. Intraocular pressure (IOP) measurements were taken at baseline and weekly. Optical measurements by vnOCT were longitudinally taken at baseline, 4 weeks and 7 weeks. Following week 7, ex vivo RGC counting was performed by immunostaining. Results:The dexamethasone group showed a measurable rise in IOP by week 2. Despite the IOP differences between the dexamethasone and control groups, there was not a statistical difference in RNFL thickness or total blood flow over 7 weeks. The dexamethasone group did show an increase in retinal arteriovenous sO2 difference (A-V sO2) that was significant at week 4 and 7. The RNFL VN ratio showed a significant decrease at week 4 and 7 in dexamethasone group associated with a decreased RGC count.Conclusions: RNFL VN ratio and A-V sO2 are capable of detecting early retinal alterations in the dexamethasone-induced ocular hypertension mouse model. Data analysis suggests VN ratio and A-V sO2 are correlated with RGC loss secondary to ocular hypertension, while being independent of IOP.