Infra-red photography retinal abnormalities and inner nuclear layer microcystic retinal degeneration in eyes with band atrophy of the optic nerve

Abstract

Purpose: To investigate the occurrence of hyporeflective areas (HA) of fundus abnormalities on infra-red photography (IRP) and of microcystic retinal degeneration (MRD) in the inner nuclear layer (INL) of eyes with permanent temporal visual field (VF) defects and band atrophy (BA) of the optic nerve from compressive chiasmal lesions. To verify the possible associations between such findings and with the severity of VF loss on standard automated perimetry

Methods: Forty-six eyes (29 patients) with temporal VF defects and BA and 20 healthy subjects (38 eyes) underwent 24-2 VF testing (Carl Zeiss Meditec), IRR and fd-OCT cube scans (Heidelberg Inc). Forty-nine OCT scans of each patient were analyzed (examiner blinded for diagnosis) for the presence of microcysts in the INL. Another blinded examiner analyzed the presence of HA on IRP of the fundus. Agreement of the presence of MRD on OCT and HA on IRP were assessed. Correlation between the number of scans with microcysts, the area of abnormality on IRP and the severity of VF loss were verified.

Results: HA areas were found in 19 of 46 eyes with BA and in 2 of 38 controls (p<0.001, Chi square test). Microcysts on the INL were found in 23 BA eyes and 2 controls (p<0.001). When at least two scans with microcysts were required for defining the eye as having MRD, the abnormality was then present in 18 of 46 eyes with BA and in no controls. Using two abnormal scans as the definition of abnormality both HA areas and MRD were found in 10 eyes indicating a significant agreement between the two methods (p=0.01, kappa test). There was a significant correlation between the area of abnormality on IRP and the number of scans with microcysts on OCT (r=0.41, Spearman test, p=0.004). No statistically significant correlation was also found between the severity of VF loss and both the area of abnormality on OCT and the number of scans with microcysts on OCT

Conclusions: Hyporeflective abnormality on IRP and MRD occur in a large percentage of eyes with BA of the optic nerve and temporal hemianopia from chiasmal compression, probably due to a trans-synaptic degenerative process in the retina. However both abnormalities do not appear to be correlated with the severity of VF loss suggesting that factors other than degeneration may influence its development

Keywords: 612 neuro-ophthalmology: diagnosis • 613 neuro-ophthalmology: optic nerve • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)