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Jake Sivak; Optics of the fish eye: Diverse and conserved characteristics. Journal of Vision 2005;5(12):30. doi: https://doi.org/10.1167/5.12.30.
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The fish eye consists of a single refractive structure, the spherical lens, which moves in accommodation. While very different than the mammalian eye, stimulus-response measures of accommodation demonstrate the lag/lead relationship found in humans.
Recent research has shown it is possible to induce form deprivation myopia in fish. Translucent goggles were directly sutured over the right eye of tilapia (Oreochromis niloticus), about 4 months old (26 – 63g) for 4 weeks to induce form deprivation myopia while the left eye served as an untreated contralateral control. Refractive state was measured by retinoscopy while ocular dimensions were determined from frozen sections and with ultrasound biomicroscopy. A scanning laser system was used to determine the optical quality of excised lenses. All the deprived fish eyes developed significant amounts of myopia ranging from −3.75 to −26.25 diopters (D), and averaging 10.27±1.14 D. The vitreous and anterior chambers of the treated eye are significantly longer axially. No significant change in optical quality was found between lenses of the myopic and non-myopic eyes. The fish recovered completely from the myopia five days after the goggle was removed. These results indicate that although lower vertebrates are capable of lifelong growth, their eyes are susceptible to form deprivation myopia. Thus, the visual environment is an important factor controlling ocular development in lower vertebrates, as well as in higher ones, and eye development is not strictly genetically determined. This study also indicates that lens growth and optical development is largely independent from the refractive development of the whole eye.
Ongoing research involves identifying differentially expressed retinal proteins from form - deprived myopic eyes. Ongoing work also indicates that that the tilapia eye can also respond to positive and negative defocus.
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