Normal-tension glaucoma patients who work on their smartphones in low light conditions may experience transient IOP elevation, a study in the British Journal of Ophthalmology reports.

A team of Korean researchers also found patients who had trabeculectomy surgery had lower IOP fluctuations compared with those who were treated pharmacologically.

The study included 40 eyes of 40 normal-tension glaucoma patients who were taking medication to treat their condition and 38 eyes of 38 patients who had undergone successful trabeculectomy.

Participants read a sample text and then typed it on a smartphone under low-light (100 lux) conditions. The investigators then obtained several IOP measurements: at baseline, during smartphone work at five, 15 and 25 minute intervals, and then five and 15 minutes after subjects had completed the task.

The study found the baseline IOP readings weren’t significantly different between the two groups (medication group: 13.9±1.6mm Hg; trabeculectomy group: 13.6±1.7mm Hg). After five minutes of smartphone work, however, the medication group showed significantly elevated IOP (an 11.5% increase). IOP increased by 29.9% after 25 minutes of smartphone work. Five minutes after the medication group stopped working on their cell phones, their IOP dropped below the baseline (13.1±1.7mm Hg).

In the trabeculectomy group, investigators noted IOP was elevated by 9.4% after five minutes of work. However, their IOP didn’t increase over the course of the 25-minute work period, remaining about 10.3% above baseline. Five minutes after stopping work, researchers noted the trabeculectomy group’s IOP was restored to the pre-work level, around 14.0±1.9mm Hg.