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Tiffany Tran, Karla Villafan, Kevin Z Kwan, D Joshua Cameron; Myopia progression in adult Lrp2/Bugeye fish. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5473.
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© ARVO (1962-2015); The Authors (2016-present)
Myopia occurs when light is focused prematurely on the neural retina. Zebrafish are a reliable model in terms of human vision research because they mimic much of the human visual system physiologically. By using the Optokinetic Response (OKR), many variables can be determined for both binocular and monocular visual functions. We used the OKR to calculate the visual acuity for the Low-Density Lipoprotein Receptor-Related 2 (Lrp2)/Bugeye fish binocularly and monocularly and tracked visual changes throughout adulthood. We hypothesized that visual acuity would diminish over time; an indication of myopia increase; the visual acuity as well as eye/head ratio will be used to verify if this hypothesis is proven or not.
Zebrafish were raised under normal conditions. Zebrafish binocular and monocular visual acuity was measured using the optokinetic response in Lrp2/Bugeye and quantified in cycles/degree (c/d). Visual acuity was correlated to eye and head size due to the assymetric buphthalmia present in these fish. Initial visual acuities were taken at about 4 months of age before any of the fish showed noticeable buphthalmia. Subsequent measurements tracked myopia progression for each eye independently and also correlated the corresponding binocular vision. Statistical analysis was done using SPSS.
As we had seen previously with similarly aged adult zebrafish, Lrp2/Bugeye fish had initial average visual acuities at < 0.60 c/d but were quite variable. With each progressing month, the visual acuities increased, though as an eye became larger the visual acuities quickly diminished. Visual acuity and eye/head ratios determined at several weeks and then subsequent months and compared to baseline values. As with wild-type fish their VA continued to improve with age. However, fish whose eye(s) developed buphthalmia had a significant reduction in their VA. Many fish exhibited binocular summation that enabled them to see better with both eyes despite one eye being poorer than the other. While others, had binocular inhibition or showed partial summation.
Myopia is a condition that is caused by a plethora of factors. In this experiment, visual acuity measurements were determined using the OKR in adult zebrafish. Specifically, the Lrp2/Bugeye mutant fish displayed a progressive myopia development that can be tracked longitudinally using functional studies. This model may prove beneficial for future myopia studies.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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