The stellar event of the year
You have most likely heard by now that all of the United States will have a solar eclipse on August 21st. The moon will cover part of the sun for 2 to 3 hours! It is projected that anyone within a narrow path from Oregon to South Carolina will experience a brief total eclipse. The moon will completely block the sun’s bright face for up to 2 minutes 40 seconds and day will turn into night! (Remember our good old optics friends the umbra and penumbra?!) Listed below is what the American Optometric Association, in partnership with the American Astronomical Society, has provided to safely view the eclipse.
Here are some guidelines for your patients to safely view a solar eclipse:
- The only safe way to view a partially eclipsed sun is through special-purpose solar filters, such as “eclipse glasses” or viewers that meet international standard ISO 12312-2 for safe viewing. Number 14 Welder’s glasses and solar filters over an objective lens of a telescope/camera are also appropriate. Sunglasses, smoked glass, unfiltered telescopes and polarizing filters are unsafe. If you can’t find eclipse viewers, build a pinhole projector to watch the eclipse.
- Before looking at the sun, cover your eyes with the eclipse viewers while standing still. Glance at the sun, turn away and then remove your filter. Do not remove the filter while looking at the sun.
- Only within the path of totality-and once the moon completely blocks the sun-can eclipse viewers safely be removed to view totality. Once the sun begins reappearing, however, viewers must be replaced.
- Following any experiences with discomfort or vision problems following the eclipse, encourage patients to schedule a medical eye exam for a comprehensive check-up.
Top ocular conditions related to solar eclipse viewing:
- Solar maculopathy- the Sun’s UV and IR light is still present and damaging even after a few minutes of being able to stare at the sun (more easily than on a regular day). Photochemical toxicity in the macula presents as a small yellowish-white spot with surrounding gray, granular pigmentation in the central fovea area that evolves into the pathognomonic circular red spot. The damage is via disruptions in the photo-oxidative pathway amongst the RPE and outer segments of the photoreceptor layer. Patients may experience mild-to-moderate visual acuity deficit (usually in the 20/40-20/60 range) and/or central or paracentral scotomata, along with metamorphopsia. It is appropriate to reassure the patient that recovery is spontaneous in nature and occurs over the course of 3-6 months after the inciting event, however, there is a slight percentage that visual recovery may be incomplete. No guidelines exist for the treatment of solar retinopathy. Several case reports of solar retinopathy have reported the use of steroids in the treatment of macular edema with equivocal results.
- UV keratopathy- The cornea absorbs most UV radiation. UV radiation damage to the corneal epithelium is cumulative, similar to the effects with dermal epithelium (sunburn). Ozone in the atmosphere effectively filters most of the harmful UV radiation of wavelengths shorter than 290 nm; natural UV sources, such as the sun, rarely cause injury after short exposures. However, unprotected exposures to the sun or solar eclipses
This was fun; when is the next one? The next total solar eclipse in the U.S. will occur on April 8, 2024!