A solar eclipse occurs when the moon, partially or totally, passes over the sun.
Risk of Exposure
Looking directly at the sun at any time is never recommended because of the risk of retinal damage and this applies during an eclipse.
During most of a solar eclipse, at least part of the sun's rays remain visible, therefore the sun's rays can burn the eye's retina if a viewer looks directly at the eclipse.
The retina is the delicate lining at the back of the eye that contains layers of light-sensitive nerve cells used for seeing.
Retinal burns can cause temporary or permanent vision loss based on the degree of exposure.
Light-induced retinal injuries can occur without any feeling of pain and the effects of the injuries may not appear for at least several hours after the damage is done.
The sun’s reduced radiance during an eclipse makes it far more dangerous than a transit of Venus where the sun’s radiance is reduced by only one per cent.
During partial eclipse phases our normal “aversion response” to the bright sun is reduced risking prolonged, unprotected, direct viewing and eye damage.
It is important to recognise the dangers of looking directly at the eclipse.
There are risks associated with all forms of direct viewing whether using solar filters, unprotected viewing or viewing through optical instruments.
Solar Retinopathy can be divided into two clinical categories. There is no recognised treatment for either so prevention is paramount.
True retinal burns (thermal) occur when looking through an optical instrument that concentrates the sun’s rays.
The father of modern astronomy, Galileo Galilei and laser retinal surgery pioneer Gerhard Meyer-Schwickerath both suffered lesions from solar viewing with a telescope.
Photoretinitis (phototoxic) from direct viewing of the sun represents the bulk of viewer damage.
There is considerable variability in susceptibility between individuals that is not fully explained. Such factors as age, pupil size, ocular pigmentation, photosensitising drugs, recreational drugs, alcohol, antioxidants and macular pigment density have been proposed.
Children are at most risk
Children and teenagers are most vulnerable to solar retinopathy due to the transmission characteristics of their eyes, their lack of experience in using solar filters and incomplete understanding of the dangers.
Children need special protection from direct viewing.
Watching a solar eclipse via Indirect viewing with the back turned to the eclipse or viewing live streams via the internet are the only safe methods endorsed by the Royal Australian and New Zealand College of Ophthalmologists (RANZCO).
'Turn your back to the eclipse'
- Viewing the eclipse can cause permanent visual loss;
- damage occurs rapidly without any pain;
- loss of vision does not occur until after the eclipse;
- there is no treatment and children are especially at risk.
- The ASO advises against any direct viewing of the eclipse.
Read the article by Dr Rowan Porter written for the ASO Bulletin September 2012 - Turn your back to the eclipse