Abstract
Purpose :
Circadian variation in ocular biometry and intraocular pressure (IOP) is well documented and is thought to play an important role in refractive error development. While previous studies have compared emmetropic and myopic subjects, little is known about circadian variation in hyperopia. In this study, we examine the diurnal variation of ocular biometry and intraocular pressure in subjects with and without hyperopia.
Methods :
Pre-presbyopic adults (mean (±SD) age 24.00 ±3.89 years) participated; 18 subjects were hyperopic (MSE ≥ +1.25 DS; mean group MSE = +4.33 ± 2.24 DS) and 17 were non-hyperopes (MSE < +1.25 DS; group mean MSE = -1.44 ± 2.27 DS). Nine of the non-hyperopes were myopes. Subjects had the following ocular parameters measured at 6 equally spaced time points between 8am and 9pm: Choroidal thickness (ChT) in the nine regions defined by the EDTRS protocol across the central 30° of fundus, axial length (AL) and IOP.
Results :
Group mean AL increased through the morning until 1:12pm ± 13min, and decreased throughout the rest of the day, in both groups. Group mean IOP decreased throughout the day in both groups as well. Group mean sub-foveal ChT reached a minimum value at 3:41pm ±14 min in both groups. However, peripheral ChT was different between the groups: in the hyperopic group, mean peripheral ChT reached a minimum at 6:15pm±13min, while in the non-hyperopic group it reached a minimum at 1:12pm±13min. Diurnal variation amplitudes was not statistically different between hyperopes and non- hyperopes for AL (33.89 ± 16.85μm vs 35.29 ± 29.18μm), sub-foveal ChT (19.72 ± 9.29 μm vs 22.77 ± 11.44μm), peripheral ChT (15.12 ± 9.43μm vs 13.26 ± 5.8μm), or IOP (4.17 ± 1.82mmHg vs 4.82 ± 2.1mmHg).
Conclusions :
Diurnal variation of peripheral ChT in hyperopic subjects shows a phase-delay when compared to the non-hyperopic group. This phase-delay aligns the peripheral diurnal variation in ChT more closely to the diurnal variation in AL. This is consistent with ocular growth studies in young chicks (Nickla, 2006) and pre-presbyopic humans (Chakraborty et al., 2012) where ChT and AL cycles phase-align in order to slow their growth response to ocular defocus.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.