Hyperreflectivity of Inner Retinal Layers as a Quantitative Parameter of Ischemic Damage in Acute Retinal Vein Occlusion (RVO): An Optical Coherence Tomography Study

PURPOSE: To investigate the reflectivity changes of inner retinal layers in acute retinal vein occlusion (RVO) on spectral-domain optical coherence tomography (SD-OCT) and to correlate these values with other known parameters of acute ischemic damage. PATIENTS AND METHODS: In this retrospective and observational case series, 230 eyes from 115 patients with acute RVO (central or branch) were categorized as ischemic or non-ischemic depending on fluorescein angiography (FA) images at baseline. Thickness and reflectivity of selected retinal layers were measured from SD-OCT images at baseline. Reflectivity values were correlated with other parameters of acute ischemic damage (best-corrected visual acuity (BCVA), retinal thickness, extent of macular edema, ischemic area on fluorescein angiography). The data were compared with contralateral eyes (controls). Prominent middle limiting membrane sign (p-MLM) was also registered. RESULTS: RVO reflectivity values differed significantly in all retinal layers compared to controls (P<0.001). Ischemic RVO eyes had higher optical intensity values for the innermost retinal layer (IMRL; P=0.008) and inner retinal layer (P=0.019) compared to non-ischemic cases. For all RVO eyes as well as central RVO, severity parameters like BCVA, central and total retinal thickness showed a strong correlation with the IMRL reflectivity. In branch RVO, BCVA remained significantly correlated with the IMRL reflectivity, while the thickness values showed significant correlation only for central foveal thickness in non-ischemic branch RVO type. The p-MLM was seen on OCT in 94% of the ischemic and in 66% of the non-ischemic RVO cases. CONCLUSION: Acute RVO leads to increased reflectivity of inner retinal layers with significantly higher values in the ischemic vs non-ischemic type. Increased inner retinal layers’ reflectivity correlated significantly with BCVA, retinal thickness of separate retinal layers, as well as ischemic area on FA. Quantitative non-invasive measurement of inner retinal layers’ reflectivity might be used to determine the extent of acute ischemic retinal damage in RVO.