Inducing form-deprivation myopia in fish.
OBJECTIVE
To induce form deprivation myopia in fish and investigate the role of the lens in the development of refractive error.


METHODS
Tilapia (Oreochromis niloticus), approximately 4 months old and from 26 to 63 g, were divided into three groups. Translucent goggles were directly sutured over the right eye for 4 weeks to induce form-deprivation myopia; the left eye served as an untreated contralateral control. The refractive state was measured by retinoscopy. Ocular dimensions were determined from frozen sections and with ultrasound biomicroscopy, and a scanning laser system was used to determine the optical quality of excised lenses.


RESULTS
After 4 weeks of form-deprivation treatment, all the deprived fish eyes showed development of significant amounts of myopia ranging from -3.75 to -26.25 D, with the average amounting to -10.27 +/- 1.14 D. Eye dimension measurements show that the vitreous and anterior chambers of the treated eye are significantly longer axially than those of the contralateral eyes. No significant change in optical quality was found between lenses of the myopic and nonmyopic eyes. The fish recovered completely from the myopia 5 days after the goggle was removed.


CONCLUSIONS
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 are largely independent from the refractive development of the whole eye.
Shen
Wei
W
School of Optometry, University of Waterloo, Waterloo, Ontario N2L 2G1, Canada.
Vijayan
Mathilakath
M
Sivak
Jacob G
JG
D000818:Animals; D000867:Anterior Chamber / Q000473:pathology; D001837:Body Weights and Measures; D023681:Cichlids / Q000502:physiology*; D005556:Form Perception; D009216:Myopia / Q000209:etiology*; D012029:Refraction, Ocular / Q000502:physiology; D012683:Sensory Deprivation; D014822:Vitreous Body / Q000473:pathology