Seasonal Variation in Diurnal Rhythms of the Human Eye: Implications for Continuing Ocular Growth in Adolescents and Young Adults

• Published in: Investigative ophthalmology & visual science Vol. 63; no. 11; p. 20
• Main Authors: Nilsen, Nickolai G., Gilson, Stuart J., Pedersen, Hilde R., Hagen, Lene A., Knoblauch, Kenneth, Baraas, Rigmor C.
• Format: Journal Article
• Language: English
• Published: Association for Research in Vision and Ophthalmology 25.10.2022; The Association for Research in Vision and Ophthalmology
• Subjects: Human health and pathology; Life Sciences; Sensory Organs; Visual Psychophysics and Physiological Optics; choroid; myopia; melatonin; circadian rhythm melatonin choroid ocular growth myopia; ocular growth; circadian rhythm
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.63.11.20

To investigate the diurnal rhythms in the human eye in winter and summer in southeast Norway (latitude 60°N).PurposeTo investigate the diurnal rhythms in the human eye in winter and summer in southeast Norway (latitude 60°N).Eight measures (epochs) of intraocular pressure, ocular biometry, and optical coherence tomography were obtained from healthy participants (17-24 years of age) on a mid-winter's day (n = 35; 6 hours of daylight at solstice) and on a day the following summer (n = 24; 18 hours of daylight at solstice). Participants wore an activity monitor 7 days before measurements. The epochs were scheduled relative to the individual's habitual wake and sleep time: two in the day (morning and midday) and six in the evening (every hour until and 1 hour after sleep time). Saliva was collected for melatonin. A linear mixed-effects model was used to determine significant diurnal variations, and a sinusoid with a 24-hour period was fitted to the data with a nonlinear mixed-effects model to estimate rhythmic statistics.MethodsEight measures (epochs) of intraocular pressure, ocular biometry, and optical coherence tomography were obtained from healthy participants (17-24 years of age) on a mid-winter's day (n = 35; 6 hours of daylight at solstice) and on a day the following summer (n = 24; 18 hours of daylight at solstice). Participants wore an activity monitor 7 days before measurements. The epochs were scheduled relative to the individual's habitual wake and sleep time: two in the day (morning and midday) and six in the evening (every hour until and 1 hour after sleep time). Saliva was collected for melatonin. A linear mixed-effects model was used to determine significant diurnal variations, and a sinusoid with a 24-hour period was fitted to the data with a nonlinear mixed-effects model to estimate rhythmic statistics.All parameters underwent significant diurnal variation in winter and summer (P < 0.002). A 1-hour phase advance was observed for melatonin and ocular axial length in the summer (P < 0.001). The degree of change in axial length was associated with axial length phase advance (R2 = 0.81, P < 0.001) and choroidal thickening (R2 = 0.54, P < 0.001) in summer.ResultsAll parameters underwent significant diurnal variation in winter and summer (P < 0.002). A 1-hour phase advance was observed for melatonin and ocular axial length in the summer (P < 0.001). The degree of change in axial length was associated with axial length phase advance (R2 = 0.81, P < 0.001) and choroidal thickening (R2 = 0.54, P < 0.001) in summer.Diurnal rhythms in ocular biometry appear to be synchronized with melatonin secretion in both winter and summer, revealing seasonal variation of diurnal rhythms in young adult eyes. The association between axial length and seasonal changes in the phase relationships between ocular parameters and melatonin suggests a between-individual variation in adaptation to seasonal changes in ocular diurnal rhythms.ConclusionsDiurnal rhythms in ocular biometry appear to be synchronized with melatonin secretion in both winter and summer, revealing seasonal variation of diurnal rhythms in young adult eyes. The association between axial length and seasonal changes in the phase relationships between ocular parameters and melatonin suggests a between-individual variation in adaptation to seasonal changes in ocular diurnal rhythms.