Abstract
Purpose :
Late bedtime was identified as a risk factor for childhood myopia and disturbance to the sleep/wake cycle was found to induce myopia in chicks accompanied with altered axial length (AL) diurnal rhythms. This study explored the relation between participants’ habitual bedtime, diurnal changes in AL and refractive status.
Methods :
A total of 25 young, healthy adults (mean age ± SD: 25±4.75 years; 13 myopes, 52%; spherical equivalent mean ± SD: -1.45 ± 1.90D) attended seven consecutive visits over 24 hours. All participants had a best-corrected visual acuity of 20/20 or better, and no history of travelling across different time zones within one month before participating in the study. At each visit, noncycloplegic open-field auto-refraction (NVision-K 5001; Shin-Nippon, Japan) and ocular biometry (LenStar; Haag-Streit, Switzerland) of the right eye was conducted. Myopia was defined as spherical equivalent ≤-0.75D. Sleep habits including usual bedtime were assessed using questionnaires (Pittsburgh Sleep Quality Index, PSQI) at the first visit; those with a usual sleep time of 12am or later were categorised as late sleepers (n=16). Diurnal changes in AL were analysed using repeated measures ANOVA, where repeated visits were modelled as the within-patient factor and usual bedtime categories and refractive status (myopic/non-myopic) were used as between-subjects factors.
Results :
Significant time-related differences in AL were observed over the 24-hour period (p < 0.001). The diurnal patterns of AL were different between early versus late sleepers (p = 0.01). Specifically, while the patterns amongst early sleepers presented a bi-phase rhythm, such characteristic was less apparent for late sleepers. The maximum and minimum values of AL were detected at different times for the two groups, with late sleepers lagging four hours behind (Fig. 1). Additionally, late sleepers were more myopic compared to the early ones (-1.83±2.01D vs -0.78±1.55D, p = 0.04) after adjusting for age and gender.
Conclusions :
In this adult population, diurnal rhythm in AL varied between early versus late sleepers and late sleepers exhibited greater myopic refractive error. The effect of the variation in sleep and diurnal rhythm in AL needs investigation in children to determine if it has a role to play in the onset of myopia.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.