Solar retinopathy

• The sun or an eclipse should never be viewed with the naked eye. Children are especially vulnerable and must always be supervised during a solar eclipse.
• Solar retinopathy (also known as eclipse retinopathy) refers to photochemical injury to the macular tissue (central retina). It is commonly associated with sungazing or eclipse viewing.
• A short duration of exposure, as little as a few seconds of fixation on the sun, can cause solar retinopathy.
• It results in mild to moderate loss of central vision, which can be permanent.
• There is no proven treatment for solar retinopathy. The mainstay of management is prevention through patient education.
• The Royal Australian and New Zealand College of Ophthalmologists (RANZCO) advises that the only way to guarantee the prevention of solar retinopathy is to avoid all forms of direct sun viewing.
• The use of solar eclipse glasses carries certain risks. Patients who use these glasses must be counselled regarding safety and precautions, including the ISO 12312-2 standard.
• Suspected cases of solar retinopathy require urgent referral to an ophthalmologist for diagnosis, and to exclude treatable causes of central visual disturbance.

Aetiology and risk factors

Solar retinopathy is caused by prolonged or high intensity exposure of the fovea centralis (central point of the macula lutea, which is responsible for high-definition colour vision) to light energy. It is typically associated with sungazing or eclipse viewing, but may be caused by laser pointers, welding, endo-illumination during ophthalmic surgery and photographical illumination mechanisms.

Predisposing factors include young age, photosensitising drugs (tetracyclines), drugs known to cause macular toxicity (Plaquenil), psychiatric disease, illicit drug use, and pre-existing macular disease, e.g. age-related macular degeneration. Men have a slightly higher incidence of solar retinopathy than women.

Pathology

Retinal phototoxicity is thought to be caused by the formation of free radicals and reactive oxygen species from incident ultraviolet energy (longer wavelength UV-A, shorter wavelengths of visible light, and near infrared wavelengths). The duration of exposure can be as short as a few seconds. It is not caused by direct thermal injury.

Phototoxicity leads to disruption of the retinal pigment epithelium (RPE; layer of cells underlying and supporting the retina), as well as damage to the choroid (blood vessels underlying the RPE) and vesiculation and fragmentation of photoreceptors. Resolution of these signs has been observed in animal models from 10 days after injury.

Diagnosis

Diagnosis is based on history, fundoscopic examination and ophthalmic imaging.

• History: onset of symptoms is usually from hours to within 1-2 days of exposure. Symptoms include unilateral or (more commonly) bilateral blurred vision, central or paracentral blind spot, altered colour vision, visual distortion (straight lines appearing curved or kinked), micropsia (objects appearing smaller than normal), photophobia and frontotemporal headache. Ask about sungazing, eclipse viewing, welding without a protective helmet, exposure to laser pointers, recent intraocular surgery and past ophthalmic history.
• Signs: visual acuity may be reduced from the level of 6/7.5 to 6/36 or worse. Fundoscopy of both eyes with a hand-held ophthalmoscope should be attempted. Findings may range from no abnormalities in mild cases, to a yellow-white spot in the central macula, progressing to a reddish spot over days.
• Imaging: diagnostic imaging is performed by ophthalmologists and includes optical coherence tomography, fundus autofluorescence and fluorescein angiography.

Differential diagnoses

Other causes of acute central visual disturbance include central serous chorioretinopathy (typically occurring in middle aged men), neovascular (‘wet’) age-related macular degeneration (typically in people aged 70 years and over) and diabetic macular oedema (patients with type 1 or type 2 diabetes mellitus).

Management

There is no proven treatment for solar retinopathy.  Systemic corticosteroids have been tried without evidence of effectiveness. Patients should be counselled to abstain from further sungazing or eclipse viewing. Those with a history of mental illness or illicit drug use should be managed appropriately. Welders should be advised to wear appropriate (industrial grade) protective helmets or goggles.

• Corticosteroids: caution should be exercised, as systemic steroids are a risk factor for other macular disease (central serous chorioretinopathy), as well as cataract formation and raised intraocular pressure.
• Anti-oxidants: ophthalmology studies have shown a benefit from taking oral anti-oxidant supplements (available over-the-counter) to slow the progression of age-related macular degeneration (ARMD). While solar retinopathy shares some features of ARMD (damage to the RPE and outer retina), there have been no studies in humans showing a benefit from anti-oxidants for solar retinopathy.
• Driving and work: patients with acute visual disturbance should exercise caution with driving, even if their visual acuity (VA) meets the requirements for a private driver’s licence (VA of at least 6/12 in the better eye). Patients with a central or para-central scotoma, or with a VA of worse than 6/12 in the better eye should not drive. Symptomatic patients who operate heavy machinery or hold a commercial driver’s licence should abstain from work altogether until they have been assessed by an eye specialist.

Prevention and patient education

The safest way of observing the sun (used by astronomers) is to project the image onto a screen. Eclipses may also be watched on televised broadcasts. The RANZCO advises that the only way to guarantee the prevention of solar retinopathy is to avoid exposure through direct sungazing of any kind.

If people decide to use eclipse glasses, it is important to minimise the risks. Further advice is as follows:

• Some commercially available solar filters have shown good absorption of visible light, as well as ultraviolet and infrared light. Only filters that meet the ISO 12312-2 standard will provide macular protection when viewing the sun or an eclipse.
• It is strongly recommended that eclipse glasses and similar products are purchased from reputable vendors, checked to confirm that they show the ISO standard certification, and not used if they appear scratched, punctured, torn or otherwise damaged.
• Even if glasses state that they meet the ISO standard, it is recommended that people visit the manufacturers website, to confirm that there are no changes or updates to the certification of the product.
• Eclipse glasses should first be used to look at a lamp or light bulb, to ensure that it can’t be seen. Only the sun should be visible through genuine eclipse glasses.
• Children should always be supervised when using approved eclipse glasses.
• Eclipse glasses may be placed over the top of normal distance glasses.
• There are risks associated with all forms of direct viewing of the sun, even through solar filters, due to: possible manufacturing faults; the availability of filters that do not meet the ISO 12312-2 standard; incorrect usage of filters, such as putting them on too late, or removing them too early during an eclipse; the risk of ‘copycat’ sungazing through filters that do not meet the ISO 12312-2 standard; the risk of ‘sneaking a peek’ without shades, especially by children. Regular sunglasses, polaroid filters, dark glasses, welding glasses, X-ray film, photographic neutral density filters, red glass filters and homemade sun filters are not safe for observing the sun.
• The sun should never be observed through an unfiltered camera, telescope or binoculars of any kind, and nor should it be viewed through these devices while wearing eclipse glasses or another form of handheld solar viewer (concentrated solar rays could damage the filter and cause solar retinopathy).
• It is never safe to look at a partial eclipse, or the partial phases of a total eclipse, without approved eye protection.

Referral to ophthalmology

Patients with suspected solar retinopathy should be urgently referred to ophthalmology, to be seen as soon as possible (within days). In rural locations, it may be more practicable to refer to a local optometrist who may be able perform telehealth with ophthalmology (see below). Where referral to optometry is not possible, travel to Perth through PATS may be arranged.  RFDS transfer is not necessary for solar retinopathy. Solar retinopathy is not a contraindication to flying.

Tele-ophthalmology in Western Australia

Tele-ophthalmology is offered through the Lions Outback Vision service.

Book a telehealth consult:
Telephone: (08) 9381 0802
Fax: (08) 9381 0700
Email: info@outbackvision.com.au
Website: outbackvision.com.au/telehealth

Prognosis

Improvement in visual acuity may occur between one and six months after injury. Good visual acuity (6/9 or better) at the time of presentation is prognostic of better visual recovery. Other deficits such as visual distortion and central or paracentral scotoma may become permanent despite an improvement in overall visual acuity.