Retina Associates’ Case of the Month: February 2013

CODM Feb 13 Edited Colour Large

Author: Michael Chilov

Editor: Adrian Fung

Figure 1.
Bilateral well demarcated yellowish subfoveal lesions, larger in the right eye.

 

A 42-year-old male was referred complaining of bilateral central visual disturbance.

Case History

A 42-year-old Caucasian male presented to his optometrist complaining of distortion of his central vision for one week. When driving he had trouble reading the central characters of automobile number plates. There was no particular precipitant he could recall. His optometrist noted bilateral foveal lesions (Figure 1) and referred him for a further opinion.

Past ophthalmic history was unremarkable. He had no medical conditions and was not taking any medications. There was no known family history of eye disease.

Examination revealed bilateral, isolated, well-demarcated, round, yellowish subfoveal lesions, slightly larger in the right eye. There was no associated haemorrhage or retinal oedema. The remainder of the fundus examination was unremarkable. The anterior segments and intraocular pressures were normal.

What is your diagnosis?

Differential diagnosis

The differential diagnosis for bilateral foveal lesions includes:

  • Macular dystrophy (e.g. Best disease, pattern dystrophy or achromatopsia)
  • Bilateral vitreomacular interface disease (e.g. macular hole, vitreomacular traction syndrome)
  • Solar retinopathy
  • Cystoid macular oedema
  • Drug-related (e.g. Hydroxychloroquine toxicity)
Additional history and investigations

Macular optical coherence tomography (OCT) showed outer retinal hyperreflectivity, with increased signal at the junction of the ellipsoid layer (inner/outer segment junction) and RPE (Figure 2). This increased signal reflectivity extends subfoveally. There was no subretinal vitelliform material, nor evidence of macula hole or vitreomacular traction.

Fundus autofluorescence imaging demonstrated pinpoint hypoautofluorescent foveal lesions (Figure 3). Fluorescein angiography demonstrated bilateral window defects corresponding to the visible lesions (Figure 4). There were no other angiographic abnormalities.

 

Figure 2.
Right and left optical coherence tomography images demonstrating outer retinal signal disturbance at the fovea. There is increased signal reflectance at the ellipsoid layer (inner/outer segment junction) and disturbance of the RPE signal. The increased signal reflectivity extends subfoveally. There is no evidence of macular hole or vitreomacular traction and retinal thickness is normal.

 

Figure 3.
Fundus autofluorescence demonstrates hypoautofluorescent lesions at both foveae.

Figure 4.
The fluorescein angiogram demonstrated bilateral hyperfluorescent window defects.

On further direct questioning regarding solar eclipse, sun gazing or work related exposure the patient admitted to a long history of sun gazing. He would stare at the sun, at sunset, for up to 28 minutes in the expectation of spiritual benefit.

 

Diagnosis

Solar retinopathy.

Clinical Course

The diagnosis and causality were explained to the patient, with the extreme dangers of sun gazing emphasised. No intervention could be offered. The patient elected not to return for further follow up. He declared he would abandon sun gazing.

Discussion

Solar retinopathy results from photochemical and thermal injury to the photoreceptors and RPE. Most cases are reported after unprotected observation of a solar eclipse. It has also been reported in sun gazers, practicing staring at the sun for perceived spiritual fulfilment, schizophrenic patients, and those with vocational exposure such as pilots and astronomers.1,2 It is a tragic irony, that a number of important scientists including Galileo Galilei, the father of astronomy, and Gerhard Meyer-Schwickerath, the pioneer of retinal photocoagulation, have suffered solar retinopathy.1

History and a compatible examination are important in making the diagnosis, with patients reporting decreased vision, central scotoma, dyschromatopsia and/or metamorphopsia shortly after viewing the sun.2 A yellowish spot at the fovea, usually inferior or immediately adjacent to the foveal light reflex may be seen in the first few days after exposure.2 Over the next few weeks this may evolve into a reddish, well-demarcated cyst-like lesion followed by foveal hypopigmentation.2 The “burn” is usually larger in the dominant eye, as is the case in our right eye dominant patient.

OCT is useful in diagnosing solar retinopathy, especially when the history of exposure is difficult to elicit. Findings vary according to the severity and duration following the injury. In acute solar retinopathy, the reported OCT findings vary but typically involve the outer retina, photoreceptors and RPE, as in our case.5 This is consistent with the histopathology of two eyes enucleated within a week of onset of solar retinopathy.6 The reported OCT findings within a week of exposure include a defect in IS/OS5,7 and decreased reflectivity of the RPE.5,7,8 Sometimes the inner retina may be involved with full thickness hyperreflectivity,7-9 but retinal thickness remains normal5,7-9. Interestingly pathology specimens of solar retinopathy vary in the degree of RPE injury and this may explain the spectrum of OCT findings reported in the early stage of the injury. In established solar retinopathy the most consistent finding is of focal foveal signal loss in the ellipsoid layer (IS/OS junction).3 The OCT may also offer prognostic information, with an optically empty space in the foveolar photoreceptor band being associated with poorer visual prognosis.4 Differential diagnoses such as macular hole and vitreomacular traction syndrome can also be excluded by OCT.

Fundus autofluorescence demonstrates hypoautofluorescence due to loss of lipofuscin at the site of photoreceptor and RPE damage. This contrasts with vitelliform lesions such as in Best disease, where hyperautofluorescence from subretinal lipofuscin is expected. Fundus autofluorescence is also useful to detect extrafoveal abnormalities that might be observed in some retinal dystrophies or following drug toxicity. Fluorescein angiogram may be normal or demonstrate a window defect but is not believed to be as sensitive as OCT.3

The visual prognosis for solar retinopathy tends to be good with an often rapid improvement in vision and symptoms in the months following exposure. Most patients present with visual acuity 6/7.5 to 6/30, recovering to 6/6 to 6/9.1 However many still report a persistent small central scotoma.

 

 

Take home points
  • Solar retinopathy may present initially with well-demarcated bilateral yellowish foveal lesions.
  • Early optical coherence tomography findings demonstrate outer retinal disturbance, at the level of the photoreceptors and RPE, with a characteristic focal signal loss in the ellipsoid layer in established ases.
  • Visual prognosis is generally good although a small central scotoma may persist.
  • Eye care professionals should warn their patients and communities of the dangers of sun gazing, especially at times of solar eclipse.

 

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References
  1. Yannuzzi LA, Fisher YL, Slakter JS, Kreuger A. Solar retinopathy: A photobiologic and geophysical analysis. Retina 1989 9: 28-43.
  2. Agarwal A. Gass’ Atlas of Macular Diseases, 5th Ed. Elsevier, 2012.
  3. Jain A, Desai R, Charalel RA et al. Solar retinopathy: Comparison of Optical Coherence Tomography (OCT) and Fluorescein angiography (FA). Retina 2009 29: 1340-1345.
  4. Gulkilik G, Taskapili M, Kocabora S et al. Association between vision loss and optical coherence tomography findings in patients with late solar retinopathy. Retina 29: 257-261
  5. Cho HJ, Yoo ES, Kim CG, Kim JW. Comparison of spectral-domain and time-domain optical coherence tomography in solar retinopathy. Korean Journal of Ophthalmology 2011 25: 278-281.
  6. Hope-Ross MW, Mahon GJ, Gardiner TA, Archer DB. Ultrastructural findings in solar retinopathy. Eye 1993 7: 29-33.
  7. Hossein M, Bonyadi J, Soheilian R et al. Specral-domain optical coherence tomography features of mild and severe acute solar retinopathy. Ophthalmic Surgery, Lasers and Imaging 2011 42: Online:e84-86.
  8. Codenotti M, Patelli F, Brancato R. OCT findings in patients with retinopathy after watching a solar eclipse. Ophthalmologica 2002 216:463-466.
  9. Bechmann M, Ehrt O, Thiel MJ et al. Optical coherence tomography findings in early solar retinopathy. British Journal of Ophthalmology2000 84: 547-548.
Disclaimer

Care has been taken to confirm the accuracy of the information present and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the contents of the publication. Application of this information in a particular situation remains the professional responsibility of the practitioner; the clinical treatments described and recommended may not be considered absolute and universal recommendations.