Visual conditions affecting eye growth alter diurnal levels of vitreous DOPAC.

D L Nickla, S Sarfare, B McGeehan, W Wei, J Elin-Calcador, L He, S Dhakal, J Dixon, M G Maguire, R A Stone, P M Iuvone

Experimental eye research 2020 Nov

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In chicks, the diurnal patterns of retinal dopamine synthesis and release are associated with refractive development. To assess the within-day patterns of dopamine release, we assayed vitreal levels of DOPAC (3,4-dihydroxyphenylacetic acid) using high performance liquid chromatography with electrochemical detection, at 4-h intervals over 24 h in eyes with experimental manipulations that change ocular growth rates. Chicks were reared under a 12 h light/12 h dark cycle; experiments began at 12 days of age. Output was assessed by modelling using the robust variance structure of Generalized Estimating Equations. Continuous spectacle lensdefocus or form deprivation: One group experienced non-restricted visual input to both eyes and served as untreated "normal" controls. Three experimental cohorts underwent monocular visual alterations known to alter eye growth and refraction: wearing a diffuser, a negative lens or a positive lens. After one full day of device-wear, chicks were euthanized at 4-h intervals over 24 h (8 birds per time/condition). Brief hyperopic defocus: Chicks wore negative lenses for only 2 daily hours either in the morning (starting at ZT 0; n = 16) or mid-day (starting at ZT 4; n = 8) for 3 days. Vitreal DOPAC was assayed. In chicks with bilateral non-restricted vision, or with continuous defocus or form-deprivation, there was a diurnal variation in vitreal DOPAC levels for all eyes (p < 0.001 for each). In normal controls, DOPAC was highest during the daytime, lowest at night, and equivalent for both eyes. In experimental groups, regardless of whether experiencing a growth stimulatory input (diffuser; negative lens) or growth inhibitory input (positive lens), DOPAC levels were reduced compared both to fellow eyes and to those of normal controls (p < 0.001 for each). These diurnal variations in vitreous DOPAC levels under different visual conditions indicate a complexity for dopaminergic mechanisms in refractive development that requires further study. Copyright © 2020 Elsevier Ltd. All rights reserved.

Citation

D L Nickla, S Sarfare, B McGeehan, W Wei, J Elin-Calcador, L He, S Dhakal, J Dixon, M G Maguire, R A Stone, P M Iuvone. Visual conditions affecting eye growth alter diurnal levels of vitreous DOPAC. Experimental eye research. 2020 Nov;200:108226