Purpose: This study aimed to investigate the effect of reading-light color on intraocular pressure (IOP) and its fluctuation in the dominant and auxiliary eyes.
Design: Correlational research and analysis.
Subjects: Fourteen subjects, aged 20 to 25 years, with a diopter ranging from 0 to -8D, were included.
Method: Subjects were instructed to read a book with a 12-pt text under white light (5,500 K) and candlelight (1,700 K), separately, for 90 minutes. Their intraocular pressures (IOPs) under their own readable brightness were measured by using a tonometer (NIDEK NT-530P) every 30 minutes. The readable brightness, reading-light spectrum and the corresponding maximum permissible exposure-limit (MPE) were measured using a blue-hazard quantitative spectrometer (SRI-100).
Main Outcome Measure: IOP of subjects after reading books under white light and candlelight for 90 minutes.
Results: Colors of reading light indeed had profound effects on IOP, and their effects were very different for the dominant and auxiliary eyes. Under white light, the IOP in the dominant eye barely increased (P=0.6), but fluctuated significantly with the increase in reading time (P=0.04). In contrary, in the auxiliary eye, it did not fluctuate (P=0.28). Instead, it slowly increased with time (P=0.01, r=0.982).
Under candlelight, the IOP also fluctuated in the dominant eye, but to a less significant extent (P=0.045). Moreover, in the auxiliary eye, it did not increase, but gradually decreased with the increase in reading time (P=0.001, r=-0.997).
Furthermore, myopic diopter showed effects on the IOPs of both dominant and auxiliary eyes. In general, the IOP increased with the increase in myopic diopter. For subjects with mild or moderate myopia, the IOP in the dominant eye, either under white or candlelight, barely increased as the reading time increased, indicating a better IOP adjusting ability. As to the subjects with high myopia, their IOP increased with the increase in reading time, with a P value of 0.08 under white light and 0.05 under candlelight.
Conclusion: Different reading-light colors showed significantly different effects on IOP. Reading under blue-emission-free candlelight can effectively prevent the increase in IOP and reduce its fluctuation. Myopic diopter showed effects on the IOPs of both dominant and auxiliary eyes. In general, the IOP increased with the increase in myopic diopter.
Clinical trial registration: 110-136-F, 28-March-2023