Spectral-domain optical coherence tomography findings in chronic solar retinopathy.

Introduction

Solar retinopathy is a clinical entity caused by any form of sun gazing most commonly attributed to solar eclipse viewing.[1] Other common causes include sunbathing, religious ritual, involving sun gazing, psychiatric illness, and military activities.[1] Solar retinopathy causes central visual distortion/loss. Acute cases present with typical history of sun exposure and easy to diagnose, but chronic cases are of challenge. Spectral-domain optical coherence tomography (SD-OCT) is a great tool to provide details comparable to histological changes. Here, we are discussing a patient with solar retinopathy diagnosed with the help of SD-OCT.

Case Report

A 66-year-old female was referred to our center with complaint of no improvement of visual acuity in the left-eye after cataract surgery, which was done 6 months back. Her best-corrected visual acuity (BCVA) was 20/20 in the right eye and 20/40 in the left eye, respectively. The anterior segment examination was normal in both the eyes. Dilated fundus examination was performed, which showed dull foveal reflex with RPE changes in her left fovea. Fundus examination of the right eye was unremarkable. Fluorescein angiography showed a minimal leak at fovea during late phase in the left eye. SD-OCT scan of the left eye demonstrated central foveal thinning along with two hypo-reflective vertical band showing disruption in outer- and inner-segment junction along with photo receptor damage [Figure 1]. When SD-OCT was acquired in 3D mode and magnified for image analysis in detail, retinal pigment epithelium (RPE) disruption was seen at left vertical hypo-reflective band [Figure 2]. Vitreoretinal interface was found to be normal in both the eyes. After assessment of SD-OCT findings, patient revealed exposure to solar eclipse with naked eyes few years back.

Figure 1

SD-OCT line scan of the left eye showing central foveal thinning along with two hypo-reflective vertical band, which depict the photoreceptor damage and disruption of the inner-and outer-segment (IS–OS) junction

Figure 2

3-Dimensional SD-OCT scan demonstrating the RPE disruption at left vertical hypo-reflective band

Discussion

The retina is prone to get damaged by solar radiation exposure beyond its defense mechanisms. Thermal, photochemical, and photomechanical reactions are suggested to be the pathogenic mechanisms for solar retinopathy.[12]

SD-OCT showed a vertical band of hypo-reflectivity caused by damage to inner- and outer segment junction along with differential RPE disruption. These findings are in correlation with the previous histopathological studies showing pre-dominant damage to the outer-retinal tissue.[34] Our findings are in agreement with Hope-Ross et al.[3] who found outer-segment of photoreceptors to be more susceptible than RPE to solar radiation while histopathological report by Tso and Woodford have shown more of RPE changes.[4] Both the above studies have shown acute changes, but our case has chronic history of sun gaze during solar eclipse. This could be explained by either some RPE recovery (right vertical hypo-reflective band) after acute injury.

Although previous reports have demonstrated outer retinal injury with the use of stratus OCT (Carl Zeiss MediTec Inc., Dublin, CA),[5] SD-OCT is able to show the additional features such as possibility of partial RPE recovery or differential effect of solar radiation along with healthy adjacent retinal tissue due to its high resolution.

In conclusion, our results are in agreement with previous OCT and histopathological reports. We have shown that in long term, solar injury mainly confined to outer retina and there is possibility of RPE recovery. Uneven reflex blink response could be the cause of unilateral solar retinopathy in this case. To understand more about its acute effects and tissue changes in due course along with its clinical effects, there is need of SD-OCT evaluation to be done at different time points.