Smartphone usage at night linked to transient blindness: NEJM Study
Impaired vision medically understood as’ Transient monocular vision loss’ is not always thromboembolic. In other words if anyone goes through temporary blindness it may not be because of the obstruction of a blood vessel by a thrombus that has become detached from its original site.
This became evident with new observations made in the the Journal New England Journal of Medicine.
The study began on the note of two women who were suffering from night impairment of vision and were brought in and put under observation. Interesting facts came to light .One of them , a 22 year old, presenting recurrent faulty vision in the right eye in the night, was discovered with normal ophthalmic and cardiovascular condition. Her Vitamin A levels and the results of magnetic resonance angiography, echocardiography, and a thrombophilia screening were also normal.
The second, a case of a 40 year old woman, with a six month history of impaired vision on waking, when screened was also found normal. Her reports on vascular cause had no reason to worry. She was also undergoing aspirin therapy .
Contrary to these normalcy reports, the two when examined at a neuro –pothalmic clinic, revealed visionary impairment. The reason discovered was several minutes of viewing a smart phone screen in the dark and after waking up, in the two cases, individually.
Their observations of themselves revealed that the eye collateral to the side on which they lay in bed, suffered vision impairment.
The conclusion reached based on their observations was that vision impairment in both these cases was due to differential bleaching of photopigment.
It was observed that the viewing eye became used to the light exposure, while the other covered by a pillow, adapted itself to the darkness.
Subsequently, when both the eyes were opened in the dark, it took the light adapted eye some time to regain vision.The recovery of sight in this case is to be understood as the time required for scotopic recovery after the bleach.
A study approved by the research ethics committee, had two authors conduct an experiment on themselves . The authors monocularly viewed a smartphone screen at arm’s length and quantified the time course of recovery of sensitivity in the dark, both psychophysically and electrophysiologically
They concluded that visual sensitivity was appreciably reduced after smart phone usage. According to them it took several minutes for vision to return. This reduction of vision being measurable at the level of the retina.
Manufacturers are producing screens with increased brightness to offset background luminance and thereby allow easy reading.
Keeping the needs of the time in mind, an understanding of retinal physiology can reassure both patient and doctor and lead to avoidance of unnecessary anxiety and costly investigations.
You can refer to the study from the following link