Sun. Feb 5th, 2023
This is what happens to your retina when you view an eclipse without protection

Americans are making their last dashes for eyeglasses and binoculars to see the rare total solar eclipse that will glide over the mainland US on Monday. Meanwhile, ophthalmologists are trying to clear up all the spinning debris clouding safety information about vision — and highlight the dangers of unsafe vision.

Everyone knows that watching a solar eclipse – or staring into the sun in general – can damage the eyes. But in a series of articles published Friday in JAMA and JAMA Ophthalmology, a group of ophthalmologists explain in detail how sunlight damages the retina, dispelling some misconceptions about viewing techniques for the rare event. They also provide a case study of what happens when you eyeball into an eclipse event.

David Calkins and Paul Sternberg of The Vanderbilt Eye Institute in Nashville, Tennessee, (which will experience a total solar eclipse) wrote one of the pieces JAMA Ophthalmology. In it, they point out that many people have the misconception that an eclipse allows for safe viewing of the sun — that the lunar disk will cover everything except the sun’s beautiful corona. This applies to the lucky ones along the path of the total solar eclipse, albeit only briefly. For those on the path of totality, the core of the Sun will not be obliterated for more than two minutes and 41 seconds. “However, for most people, at least part of the sun’s core will be visible during the event,” Calkins and Sternberg note.

If viewers of the total eclipse take their protection off, it’s important to have it back in place before the moon starts to move to the side. Otherwise you risk damage. Everyone else must be careful all the time.

Core sunlight is intense, at about 1,350 watts per square meter, they note. With the refracting nature of our eyes, this leads to a hefty dose to the tiny 1.5mm fovea – the central pit of the retina. This pit is full of photoreceptor cone cells responsible for seeing colors and giving us our sharp central vision.

Sunlight damages the eye in two different ways

Exposing your naked eyeball to sunlight causes solar retinopathy (also called photic retinopathy or solar retinitis), which involves two types of damage to the retina, specifically the fovea: burns and photochemical toxicity.

The first is perhaps the easiest to understand. Much of sunlight is near-infrared radiation (700 to 1,500 nanometers), which can cause heat and thus burns, Calkins and Sternberg note. Because our eyes don’t have pain receptors, we can scorch the fovea without noticing it while staring at the sun.

But, the eye experts write, a “more pressing concern” is photochemical toxicity. The large amount of visible light from the sun is gobbled up by photoactive materials in the eye that just itch to form free radicals and reactive oxygen species. These include heme proteins, melanosomes, lipofuscin and other chemicals. Once generated, free radicals and reactive oxygen species can attack many types of molecules and break down membranes, leading to tissue damage and cell death. Once retinal tissue is destroyed, it cannot regenerate.

The authors say a study of 45 people who damaged their eyes during a 1999 solar eclipse in the UK supports the idea that photochemical toxicity is a frequent cause of vision damage in solar retinopathy. In those cases, most of the damage was not permanent. Only four of the 45 reported persistent symptoms – discomfort and vision problems – after seven months.

But irreversible damage is of course more likely with longer and greater exposures. A case report published by Ta C. Chang and Kara Cavuoto of the University of Miami’s Bascom Palmer Eye Institute describes permanent injuries in a 12-year-old girl. She suffered severe vision loss after staring at the full sun for about a full minute. The eye experts presented images of her damaged retina, one of which was obtained by optical coherence tomography (OCT), a type of ultrasound for the eye that uses light to create cross-sectional tissue images. The images show bright pitted areas (see white arrows) in her fovea where photoreceptor segments have been obliterated by sun damage. At follow-up examinations, her vision had not improved.

infrared (A) and macular optical coherence tomography (OCT) (B) images demonstrating a hyperreflective spot in the fovea (arrowheads), presumably a disruption of the inner and outer photoreceptor segments with no evidence of underlying retinal pigment epithelial defects, consistent with bilateral solar retinopathy .
Enlarge / infrared (A) and macular optical coherence tomography (OCT) (B) images demonstrating a hyperreflective spot in the fovea (arrowheads), presumably a disruption of the inner and outer photoreceptor segments with no evidence of underlying retinal pigment epithelial defects, consistent with bilateral solar retinopathy .

The JAMA Network

Here’s how to prevent such damage

In JAMANeil Bressler, of Johns Hopkins University School of Medicine, and colleagues explain how to safely view the eclipse.

First, what not to do: Do ​​not view the eclipse with your naked eye or unfiltered telescopes, binoculars, sunglasses (yes, even if they are very dark), camera lenses or other optical devices. Don’t use anything that focuses light, even if you’re wearing eclipse glasses. NASA notes that the concentrated sun rays can damage the filter and get into your eyes.

To watch the eclipse safely, go to:

  • No. 14 welder goggles, available at welding supply stores.
  • Pinhole Projectors. It allows you to see the eclipse by projecting sunlight through a pinhole onto a visible surface (Note: it’s not just looking through a pinhole). Here you will find more information about this.
  • Aluminized Mylar filters / commercial glasses that have no damage or scratches. The American Astronomical Society says these must be verified by an accredited testing lab to meet the international safety standard ISO 12312-2. Beware, there are scammers out there. The AAS has a handy list of reputable versions on their website.

If you are concerned that your eyes have been damaged by sunlight, see an ophthalmologist immediately, who can diagnose you with a clinical evaluation and diagnostic tests, such as OCT.

JAMA2017. DOI: 10.1001/jama.2017.9495 (About DOIs).

JAMA Ophthalmology2017. DOI: 10.1001/jamaophthalmol.2017.2936

By akfire1

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