Acute solar retinopathy visual loss may resolve with time and patients may regain good visual acuity [7
]. Although return of good visual acuity may occur, some patients continue to experience visual deficiencies such as a small persistent central or paracentral scotoma due to chronic solar damage to the photoreceptors and the RPE leading to retinal atrophy and degeneration [3
]. Pathology may depend on the intensity, duration and light spectrum of solar exposure, ocular pigmentation, clarity of the ocular media and environmental conditions such as highly reflective surroundings and reduced atmospheric ozone [9
Solar retinopathy was first described using time domain OCT by Bechmann and colleagues where they found a hyper-reflective area at the fovea and all retinal layers were affected [12
]. Several studies using earlier modalities of OCT have shown transient increase in foveal reflectivity [12
], reduced reflectivity from the retinal pigment epithelium [3
] or disruption of the inner segment and outer segment of the photoreceptor layers [8
]; but each case series demonstrated that OCT retinal structural alterations may not be consistent in every case of solar retinopathy [2
]. Acute changes seen on OCT from solar retinopathy have been described to affect predominantly the outer photoreceptor segments and may even resolve with time [3
]. Patients with a chronic history (at least 1 year or more) of solar retinopathy exposure primarily have disruption between the inner and outer segments of photoreceptors [4
In the present study, utilizing the high definition imaging from the Spectralis SD-OCT (Heidelberg Engineering, Vista, California, USA), solar retinopathy was shown to specifically damage the inner and outer segment of the photoreceptors in both acute (Cases 1 and 2) and chronic (Case 3) presentations, without involvement of the RPE. In the literature review, RPE defects were more prominent in the acute exposure group based on the odds ratio (p = 0.04) and photoreceptor defects were found more often in the chronic exposure group (p = 0.02). While this was significant, RPE defects were still observed in the chronic exposure group and photoreceptor defects were also seen in the acute exposure group. Losses at the RPE layer may represent photochemical damage to the pigmented RPE layer [5
], and acute disruption of the outer segment layer from solar exposure may be secondary to loss of RPE function therefore indirectly affecting the photoreceptor segments [4
Not only are these OCT changes correlated with time from exposure to exam, time interval also affects visual acuity. Less than one year from exposure to examination showed better visual acuity when compared to more than one year from exposure (p < 0.001). It is possible that acute sun exposure causes damage to both the RPE and photoreceptor layers, and in chronic cases leads to permanent disruption of the inner and outer segments with photoreceptor cells demonstrating vesiculation and fragmentation of the photoreceptor lamellae [6
]. Presence of optically empty spaces or full-thickness disruption of the whole photoreceptor band just beneath the fovea may explain permanent visual loss, whereas involvement outside of the fovea does not affect vision [13
Based on our case series and literature review, our results suggest that the photoreceptor layer may be the layer most likely to be permanently damaged by solar retinopathy and lead to overall worse long-term vision. Lesions in the RPE layer, inner high reflective layer and outer photoreceptor segment layer did not affect best corrected visual acuity. Only the inner photoreceptor lesions were significantly related to worse visual acuity (p < 0.001). One explanation for this is that the high resolution Spectralis SD-OCT allowed for better characterization of the retinal layers affected compared to previous reports. More data gathered by Spectralis SD-OCT will continue to help address this issue. Of note, several papers from the literature review used a lower resolution time domain OCT, and error may have been introduced when defining the location of the lesions.
In conclusion, this present series of patients utilizing high definition SD-OCT imaging suggests that solar retinopathy OCT findings may occur primarily at the inner photoreceptor segment layers leading to foveal atrophy. Acute changes defined as less than one year from exposure to exam tend to affect vision less than more chronic photoreceptor changes in the inner photoreceptor layer or at the junction of the inner and outer photoreceptor layers. Limitation of our study includes the number of eyes evaluated but with continued use of SD-OCT, future studies can utilize this modality of OCT imaging to analyze larger numbers of patients with solar retinopathy and elucidate possible causes of visual loss and supplement clinical exams.