Ocular and Systemic Diurnal Rhythms in Emmetropic and Myopic Adults



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Purpose: Evidence suggests that diurnal rhythms and light exposure patterns may influence the development of refractive error. This study investigated diurnal variations in anterior and posterior segment biometry and assessed differences between myopic and emmetropic adults. Ocular and systemic diurnal rhythms were also examined in relation to objectively measured light exposure and refractive error.

Methods: Healthy subjects (n = 42, 23-41 years old) underwent biometry and spectral domain optical coherence tomography imaging (SD-OCT) every 4 hours (h) for 24 h. Subjects were in darkness from 11:00 pm to 7:00 am. Central corneal thickness, corneal power, anterior chamber depth, lens thickness, vitreous chamber depth, and axial length were measured. Thicknesses of the total retina, photoreceptor outer segments + retinal pigment epithelium (RPE), photoreceptor inner segments, and choroid for a 3mm and 6mm annulus were determined. Additional measurements taken at each time point included blood pressure, heart rate, body temperature, and intraocular pressure (IOP). Mean ocular perfusion pressure (MOPP) was calculated. Saliva was collected for melatonin and cortisol analysis. Subjects wore a light, sleep, and activity monitor for one week prior to measurements. Acrophase and amplitude for each parameter were compared between refractive error groups and relationship to light exposure was examined.

Results: All ocular and systemic parameters except anterior chamber depth demonstrated significant diurnal variations. Amplitude of axial length variation (35.71 ± 19.40 μm) was in antiphase to choroid variation (25.65 ± 2.01 μm, P < 0.001). The central 1 mm retina underwent variation of 5.03 ± 0.23 μm with a peak at 12 h (p < 0.001), while photoreceptor outer segment + RPE thickness peaked at 4 h and inner segment thickness peaked at 16 h. Diurnal variations in retina and choroid were observed in the 3 and 6 mm annuli. Melatonin increased following light offset with a peak at 3.19 h, while cortisol peaked after light onset at 8.86 h. IOP peaked at 11.24 h, with a variation of 4.92 ± 1.57 of mmHg, in anti-phase with MOPP, which peaked at 22.02 h. No parameter demonstrated a difference in diurnal rhythm between refractive error groups except for body temperature and MOPP.

Conclusion: Ocular and systemic diurnal rhythms were observed over 24 hours in adults. While differences in baseline parameters were found between refractive error groups, diurnal rhythms were not significantly different between myopes and emmetropes, except for body temperature and MOPP. Amplitudes of daily variations were not correlated with light exposure.



Myopia, Circadian rhythm, Choroid, Ocular biometry


Portions of this document appear in: Burfield, Hannah J., Nimesh B. Patel, and Lisa A. Ostrin. "Ocular biometric diurnal rhythms in emmetropic and myopic adults." Investigative ophthalmology & visual science 59, no. 12 (2018): 5176-5187.