Solar Retinopathy
Topics Details
Solar retinopathy (photo-retinitis, foveomacular retinitis, photomaculopathy, or eclipse retinopathy) is the retinal injury induced by direct or indirect exposure to light. Harmful effects of viewing sun are well recognised. Solar retinopathy may be due to looking at solar eclipse with or without telescope, sunbathing, religious gazing of sun, and use of psychotropic drugs.
The effect of light on retina is being recognised since the time of Plato, who gave description of eclipse blindness.
Photic (related to light) retinopathy is a generalised term used for retinal damage produced by light. This may be due to solar viewing or may be produced even by the use of operating microscope.
Photo-retinitis damages the retina through photochemical effects, associated with rise in temperature. Sustained viewing of sun for more than 90 seconds through a constricted pupil may exceed the threshold for damage of retinal tissues.
References
Yanoff Myron, Duker Jay S. Ophthalmology Fourth Edition. Elsevier Saunders 2014. P 461- 466.
http://eyewiki.aao.org/Solar_Retinopathy
Mild photochemical damage may not be symptomatic in patients.
Symptoms develop usually 1 to 4 hours after exposure to sun and is characterised by
- Pain around orbits.
- Diminution of vision (unilateral or bilateral).
- Central or paracentral scotoma (areas of decreased or obscure vision in the field of vision).
- Photophobia (increased sensitivity to light).
- Metamorphopsia (distorted vision).
- Chromatopsia (objects appear abnormally coloured e.g. erythropsia shows reddish colour).
- Afterimage (persistence of image even after removal of stimulus).
Control
Retinal damage to light is produced by either breakdown of the intrinsic protective mechanisms of the eye and/or to the external high risk conditions.
The development and severity of damage depends upon
Anatomic protective mechanisms of eye.
Area of tissue involved.
Wavelength of light.
Duration of light exposure.
Total energy exposure.
Mechanism
The mechanism of damage is primarily photochemical. This may be potentiated by rise in tissue temperature. Increased chorioretinal pigmentation facilitates light absorption, which increases the background retinal temperature. Retinal defences are broken by supra-normal exposure to light. Retinal phototoxicity was originally believed to be a permanent damage, but some visual recovery has been seen.
The extent of retinal injury and its possible recovery depends upon factors such as
Area of exposed retina.
Location of damage.
Spectrum, intensity and duration of light exposure.
Susceptibility of host.
Emmetropia or hypermetropia due to effective focusing of light on retina.
Systemic photosensitising agents such as tetracycline and psoralen, may predispose to damage due to light.
Diagnosis depends upon clinical history/symptoms, manifesting signs, and investigations.
Clinical signs
A small yellow spot with a grey margin may appear shortly after exposure in the foveolar or parafoveolar area. This disc shaped lesion is about 200?m in diameter which corresponds to retinal image of the sun. Mild cases may not show any lesion.
Histopathology
Acute solar lesion
Acute solar lesion shows injury to retinal pigment epithelium (RPE) with necrosis, irregular pigmentation, and detachment. Photoreceptors show minimal change only.
Weeks following acute damage
The yellow lesion is replaced by a permanent focal depression, with mottling of RPE or there may be lamellar hole. Vision may show some recovery, but scotoma and metamorphopsia may persist. Previous episodesof sun gazing show multiple areas of mottling in RPE.
Fluorescein angiography may appear normal or may show transmission defects. There may be leakage of fluorescein dye in acute cases.
Optical coherence tomography (OCT) shows disrupted reflectivity in outer retina, or fragmentation of highly reflective outer retina.
Amsler grid testing may delineate small central or paracentral scotoma.
Multifocal electroretinography (ERG) shows decrease in amplitude with normal latency of the recordings.
Differential diagnosis
- Welding-arc maculopathy.
- Light flash or arc, produced by high-voltage electrical short-circuiting.
- Other causes of lamellar depressions or holes like posterior vitreous detachment or trauma.
- Post-surgical photic retinopathy.
- Accidental laser exposure.
Remedy
In management, there is no specific therapy for solar retinopathy.
Oral corticosteroids have been used in acute lesions, but a beneficial effect is not being demonstrated conclusively.
Further episodes of solar viewing should be avoided. Eclipse viewing should be avoided unless there is proper protective eyewear. Solar filters with high quality of filtration of absolute visible, ultraviolet, and infrared light are recommended for viewing of eclipse.
Prognosis
Prognosis is guarded. Some improvement often occurs. Part of the defect usually remains, and the visual scotoma may persist permanently.
Many patients of solar retinopathy do not develop complications and return to normal vision with resolution of symptoms over weeks and months. Some patients may develop
- Permanent diminution of vision.
- Persistent metamorphopsia.
- Scotoma.
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