Not all astronomical events live up to their hype. In December 1973, when I was a senior in high school, the comet Kohoutek was touted by the media as one of the most spectacular celestial events of the time and the “Comet of the Century.” It turned out to be no more than another twinkle in the sky, presumably due to its disintegration when it passed by the sun prior to flying by Earth.
The impending total solar eclipse of 2017, crossing from Oregon to South Carolina on Monday, August 21, 2017, is not likely to disappoint. It’s unlikely to be cloudy all across its continental transit and millions will be able to see the partial or total obscuration of the sun by the moon for their first and only time.
Ophthalmologists and other physicians, though, should be aware of the contributions solar retinopathy may make to visual symptoms as they take histories and perform physical examinations and imaging after that date. Despite widely available instructions regarding prevention of solar retinopathy, and even with excellent adherence with protective measures by the public, there are at least 3 reasons why many cases of macular damage might occur.
1. Population: This is the first total solar eclipse in 99 years to cross the entire continental United States and many more people will be exposed. Not only will the eclipse cross through major cities like Nashville, Tennessee, but many people will travel from larger population centers to smaller cities and towns across the country to be present at a spot where totality will occur.
2. Adherence: Only during the approximately 90 seconds of totality can the spectacular corona (aura of bright plasma) surrounding the sun be visualized with little if any discomfort and risk. If the cautious observer in an area of totality keeps an appropriate filter in place as the eclipse begins but then removes the filter at the time of totality, that observer must remember to put the filter back in place as soon as totality ends. Ninety seconds goes by quickly and it can be difficult to differentiate the corona from the sliver of the sun that appears as totality ends. That sliver, when viewed without protection, can lead to solar retinopathy. In areas of subtotal eclipse – most of the United States – there is no time when it is safe to view the sun without proper filters, and yet there surely will be some among the millions who are tempted to take off their filters when most but not all of the sun is being obscured by the moon.
3. Imaging: Imaging techniques have improved greatly and could increase detection of subclinical solar retinopathy—from the subtle small translucent lesion in the fovea, easily overlooked with direct ophthalmoscopy for the past 100 years to the very obvious lesions now visualized by spectral domain optical coherence tomography. Thus, even asymptomatic patients being evaluated for other ophthalmic problems may have lesions that might be related to solar retinopathy if a careful history determines that the patient was viewing the solar eclipse without protection.
Ophthalmologists should encourage patients and the public to enjoy an astronomical event of the century if they can, but they should do so wisely—the fovea cannot be replaced!