Circadian rhythms and myopia

Both environmental and genetic factors contribute to the complex etiology of myopia, yet the precise causes and mechanisms underlying myopia development remain unknown.1 There is accumulating evidence in humans for an association between myopia and disturbed sleep,2 but is the circadian system involved?

In animals, changing the light-dark cycle (and thus the circadian rhythm) interferes with normal eye growth.3 This is likely mediated by changes to the ocular rhythms,4 as well as altered levels of ocular dopamine and melatonin,5 both key circadian neurochemicals. These results point to an involvement of the circadian system in eye growth regulation and refractive error development,6 but the evidence in humans is less consistent.

A recent study in young myopic adults found that their circadian timing was significantly delayed compared to that of emmetropic adults, consistent with the finding that myopic individuals tend to go to bed later. While this study supports an association between circadian phase shifts and myopia in humans,7 other experiments have not reported a difference in circadian timing between refractive error groups.8,9

Comparisons of dopamine10,11 and melatonin7,12 levels between myopic individuals and non-myopic individuals have produced similarly mixed findings that are likely attributable, at least in part, to methodological differences between studies.

More research is needed to obtain a better understanding of the involvement of circadian processes in myopia, which may be key to expanding our knowledge of the mechanisms underlying myopia development. Further research in this area could help advance treatment practices and inform healthcare professionals on how to support myopic patients who struggle with disturbed sleep.

At Dopavision, we are developing a light-based technology that aims to treat myopia digitally. We are currently preparing to launch a clinical trial to investigate the ability of our approach to slow the progression of myopia in children and adolescents. Learn more about our light-based approach to myopia treatment at on our Science page.

References

1
Morgan, I. G., Ohno-Matsui, K., & Saw, S. M. (2012). Myopia. The Lancet, 379(9827), 1739-1748.

2Liu, X. N., Naduvilath, T. J., Wang, J., Xiong, S., He, X., Xu, X., & Sankaridurg, P. R. (2020). Sleeping late is a risk factor for myopia development amongst school-aged children in China. Scientific reports, 10(1), 1-11.

3Smith, E. L., Bradley, D. V., Fernandes, A., Hung, L. F., & Boothe, R. G. (2001). Continuous ambient lighting and eye growth in primates. Investigative ophthalmology & visual science, 42(6), 1146-1152.

4Nickla, D. L. (2013). Ocular diurnal rhythms and eye growth regulation: where we are 50 years after Lauber. Experimental eye research, 114, 25-34.

5Schaeffel, F., Bartmann, M., Hagel, G., & Zrenner, E. (1995). Studies on the role of the retinal dopamine/melatonin system in experimental refractive errors in chickens. Vision research, 35(9), 1247-1264.

6Chakraborty, R., Ostrin, L. A., Nickla, D. L., Iuvone, P. M., Pardue, M. T., & Stone, R. A. (2018). Circadian rhythms, refractive development, and myopia. Ophthalmic and Physiological Optics, 38(3), 217-245.

7Chakraborty, R., Collins, M. J., Kricancic, H., Moderiano, D., Davis, B., Alonso-Caneiro, D., … & Baskaran, K. (2021). The intrinsically photosensitive retinal ganglion cell (ipRGC) mediated pupil response in young adult humans with refractive errors. Journal of Optometry.

8Burfield, H. J., Carkeet, A., & Ostrin, L. A. (2019). Ocular and systemic diurnal rhythms in emmetropic and myopic adults. Investigative ophthalmology & visual science, 60(6), 2237-2247.

9Flanagan, S. C., Cobice, D., Richardson, P., Sittlington, J. J., & Saunders, K. J. (2020). Elevated melatonin levels found in young myopic adults are not attributable to a shift in circadian phase. Investigative Ophthalmology & Visual Science, 61(8), 45-45.

10Hussain, A., Gopalakrishnan, A., Muthuvel, B., Hussaindeen, J. R., Narayanasamy, A., & Sivaraman, V. (2021). Young adults with myopia have lower concentrations of neuromodulators-dopamine and melatonin in serum and tear. Experimental Eye Research, 209, 108684.

11Kearney, S., O’Donoghue, L., Pourshahidi, L. K., Cobice, D., & Saunders, K. J. (2017). Myopes have significantly higher serum melatonin concentrations than non‐myopes. Ophthalmic and Physiological Optics, 37(5), 557-567.

12Abbott, K. S., Queener, H. M., & Ostrin, L. A. (2018). The ipRGC-Driven Pupil Response with Light Exposure, Refractive Error and Sleep. Optometry and vision science: official publication of the American Academy of Optometry, 95(4), 323.