Looking at your smartphone while lying in bed at night could trigger a temporary loss of vision, according to a study published in The New England Journal of Medicine.
Although the symptoms can often be mistaken for a mini-stroke, experts at Moorfields Eye Hospital have noticed the symptoms, which usually last around 15 minutes, can be the result of looking at a screen in bed.
The study looked at two patients who attended the neuro-ophthalmology clinic at Moorfields Eye Hospital after experiencing recurring episodes of temporary vision loss.
A 22-year-old woman presented with a several months’ history of recurrent impaired vision in the right eye that occurred at night. The results of ophthalmic and cardiovascular examinations were normal. Vitamin A levels and the results of magnetic resonance angiography, echocardiography, and a thrombophilia screening were also normal.
The second case involved a 40-year-old woman who presented with a six-month history of recurrent monocular visual impairment on waking, lasting up to 15 minutes. The results of investigations for a vascular cause were again normal. Aspirin therapy had been commenced.
When the patients were seen at Moorfields Hospital neuro-ophthalmic clinic, detailed history taking revealed that symptoms occurred only after several minutes of viewing a smartphone screen, in the dark, while lying in bed (before going to sleep in the first case and after waking in the second). Both patients were asked to experiment and record their symptoms. They reported that the symptoms were always in the eye contralateral to the side on which the patient was lying.
Mr. Gordon Plant, consultant neurologist at Moorfields, explained that both patients typically looked at their smartphones with only one eye while resting on their side in bed in the dark – their other eye was covered by the pillow. While one eye adapts to the dark, the other gets used to the light of the device. When you open both eyes, the one that has been staring at the screen cannot cope with the darkness and can experience temporary perceived blindness.
It was hypothesised that the patients’ symptoms were due to differential bleaching of photopigment, with the viewing eye becoming light-adapted while the eye blocked by the pillow was becoming dark-adapted. Subsequently, with both eyes uncovered in the dark, the light-adapted eye was perceived to be “blind.” The discrepancy lasted several minutes, reflecting the time course of scotopic recovery after a bleach.
The study concluded that temporary blindness was ultimately harmless, and easily avoidable, if people stuck to looking at their smartphones with both eyes.
www.nejm.org/doi/full/10.1056/NEJMc1514294#t=article
