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Smartphone Use at Night May Result in Monocular ‘Blindness’

Transient vision loss due to optical adaptation of the eyes caused by reading smartphone with one eye

THURSDAY, June 23, 2016 (HealthDay News) — A short-lived optical sensation can lead some smartphone users to mistakenly believe they’ve lost sight in one eye, according to a research letter published in the June 23 issue of the New England Journal of Medicine.

The letter cites two case studies: a 22-year-old woman who’d suffered recurring bouts of nighttime vision loss in her right eye for several months, and a 40-year-old woman who would wake up with a loss of vision in one eye that lasted as long as 15 minutes.

Both women underwent several tests, including magnetic resonance imaging and echocardiograms, before doctors realized that the transient “blindness” was due to an optical adaptation of the eyes caused by reading a smartphone in the dark while lying on their side in bed. When one eye was occluded by the pillow and they were viewing the phone with the other eye, the occluded eye adapted to the dark and the viewing eye adapted to the light. When both eyes were uncovered in the dark, the light-adapted eye was perceived to be “blind,” an effect lasting several minutes.

“I have seen a dozen or so similar cases,” study author Gordon Plant, M.D. an ophthalmologist with Moorfields Eye Hospital in London, told HealthDay. “The reason I wish to make this known is because it leads to anxiety and unnecessary investigation because the patients — and their doctors — think they have had a transient ischemic attack.”

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