Background/aims To investigate (1) the effect of reading or writing on a smartphone in terms of intraocular pressure (IOP) change in eyes with glaucoma, and (2) to determine whether previous glaucoma filtering surgery can affect IOP fluctuation during such work.

Methods Forty eyes of 40 medically well IOP-controlled normal-tension glaucoma (NTG) patients and 38 eyes of 38 NTG patients who had undergone successful trabeculectomy (TLE) were enrolled. The participants were instructed to read a sample text and to then type it on a smartphone under low-light [100 lux] conditions. Three IOP measurements were obtained: baseline; during smartphone work (5, 15 and 25 min); post-work (5 and 15 min).

Results Baseline IOP did not significantly differ between the two groups (medication group: 13.9±1.6 mm Hg; TLE group: 13.6±1.7 mm Hg; p=0.426). After 5 min of smartphone work, the medication group showed significantly elevated mean IOP (15.5±1.8 mm Hg;+11.5%; p<0.001), along with further increases over the course of 25 min (17.5±2.2 mm Hg;+25.9%; p<0.001). 5 min after halting work, IOP dropped below the baseline (13.1±1.7 mm Hg; p<0.001). For the TLE group, IOP also was elevated after 5 min (14.9±1.7 mm Hg;+9.4%; p<0.001); however, it did not show further increase over the course of 25 min of work (15.0±1.6 mm Hg;+10.3%). At 5 min after cessation of work, IOP had restored to the pre-work level (14.0±1.9 mm Hg;+2.8%; p=0.053).

Conclusion Working on a smartphone under low-light condition can incur IOP elevation in treated NTG patients. However, among the participants in this study, IOP fluctuation was much smaller in those who had undergone TLE.