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Peony C. Tam, Faydim Rassamdana, Kathleen Dang, D. Joshua Cameron; The Use of Optokinetic Response to Quantitatively Measure Visual Acuity in Adult Zebrafish. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5713.
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The optokinetic response (OKR) has been widely used to determine visual function in larval zebrafish. Previous reports have provided cycles per degree (cpd) measurements which enable a basic visual acuity measurement to be scored in larval zebrafish. This same procedure for adult zebrafish has posed a challenge in the past, but a simple method has now been developed to reliably conduct OKR testing in adult zebrafish and measure visual acuity in cpd.
The custom built OKR recording device consists of a 14.5 cm diameter rotating drum and microscope with adjustable light intensity settings. The microscope is equipped with a camera system that provides a live feed on an adjacent monitor that also allows for image capture and recording. The rotating drum has various speed settings in both clockwise and counterclockwise directions. The adult zebrafish are first anesthetized in tricaine and then placed on a small platform with the eyes and gills suspended over the edge. A thin sponge is placed over the body of the fish, and 3 pieces of foam, shaped to accommodate the fish, are pinned on top to keep it immobilized. A cylindrical tank that fits inside of the rotating drum has a magnet where the platform can be mounted. The fish is positioned so that the eyes are approximately 7.0 cm from each edge of the drum. The OKR measurements are taken using a range of black and white spatial frequency grating patterns.
By observing the OKR reflexive eye movements of the fish, the spatial frequency threshold was determined for each individual fish and their acuity was calculated in cpd (See Figure). The absolute spatial acuity for an average 5 month old wild type (AB) zebrafish is approximately 0.46 ± 0.18 cpd.
OKR is a successful objective quantitative measurement of visual acuity in adult zebrafish. Further data collection can be useful in determining reduced visual acuities in disease models of zebrafish. Current studies that rely on behavioral methods to assess vision can be expanded further with this new development in adult zebrafish OKR data analysis.
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