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S. Crewther, D. Crewther, M. Murphy, A. Barutchu; Differential Refractive Compensation following Intravitreal Injection of NMDA and Quisqualate in Hatchling Chicks . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2807.
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Purpose: To investigate the effects of inner retinal excitotoxins NMDA and Quisqualate (QUIS) on ocular growth and on refractive compensation to optically induced defocus in hatchling chicks. Single 200nmol injections of NMDA have previously been reported to lesion amacrine cells and QUIS to lesion amacrine and horizontal cells Methods: Thirty two hatchling chicks of Leghorn/Australorp strain were raised from 7-14 days in a normally lighted 12hr day light cycle controlled environment, wearing a right eye (±10D or 0 D) lens following administration of a single 5µl intravitreal injection of either 100nmol N-methyl-D- aspartate (NMDA) or 200nmol quisqualic acid to the right eye and 5µl injection of vehicle solution to the left eye. Effects on eye growth were monitored with retinoscopy and A-scan ultrasonography. Results: NMDA and QUIS differentially affected growth compensation to the ±10D lens induced defocus with a significant interaction effect between drug and lens type F(2,25) = 5.0, p = 0.015. Mean differential compensation for +10D and -10D lens wear following NMDA was +7.3 D and +1.5 D respectively. Mean differential compensation for +10 and –10D lens wear following Quis was +6.5 and –-8.3 D respectively. Conclusions: These excitotoxins, both purported to act on inner retinal sites differentially affect compensation to optical defocus. The effects vary according to lens and drug condition, reinforcing the notion that detection and response to defocus is initiated by separate, sign dependent mechanisms.
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