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Serum and aqueous melatonin levels in myopes and its relation to sun exposure

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First Author: S.Kumar INDIA

Co Author(s):    S. Kumar   N. Gupta   V. Gupta   T. Velpandian   P. Vashist   R. Tandon     

Abstract Details

Purpose:

To explore the role of ultraviolet light exposure and circadian rhythm by estimating ocular sun exposure as measured by Conjunctival Ultraviolet Autofluorescence (CUVAF) and quantifying serum and aqueous melatonin levels in myopes and non-myopes.

Setting:

Cross sectional study done at Dr R P Centre for Ophthalmic Sciences in New Delhi, India.

Methods:

60 emmetropes and 60 myopes aged 10-25 years were included in the study. An additional group of 32 myopes was also included for estimating the aqueous levels of melatonin which was collected during the phakic intraocular lens (IOL) surgery for correction of myopia. Demographic parameters, sun exposure questionnaires, morning serum melatonin, sleep pattern, degree of myopia, ocular biometry and area of CUVAF (objective biomarker for ocular UV exposure) were noted and analysed. Aqueous melatonin was estimated in 32 myopes who underwent phakic IOL surgery.

Results:

Serum melatonin was significantly higher (P=0.001) among myopes as compared to emmetropes. Day time sleepiness was reported more in the myopic subjects (P<0.0001). Lifetime sun exposure was significantly less in myopes than emmetropes (P= 0.001). The area of CUVAF was also significantly decreased (P<0.0001) among myopes as compared to emmetropes. Serum melatonin level showed a positive correlation with axial length (P=0.002) and degree of myopia (P=0.01). Aqueous melatonin was detectable in 20 of 32 (40.6%) patients with a median value of 2.101pg/ml. Aqueous melatonin showed a rising trend with degree of myopia but it was not statistically significant.

Conclusions:

This is a pioneer study demonstrating an inverse relationship between serum melatonin and ocular UV exposure as measured by CUVAF in myopic children and young adults. Ultraviolet exposure as measured by conjunctival autofluorescence area and through lifetime UV exposure questionnaires was significantly more in emmetropes than in myopes, thus signifying a protective role of UV exposure in myopia. Hence, this study establishes the link between quantitative assessment of ocular UV exposure (CUVAF) and biochemical alterations (melatonin) in young myopes (10-25 years). Light exposure and circadian rhythm play an important role in myopes.

Financial Disclosure:

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