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A Fernandes, R Haque, M Tigges, PM Iuvone, SR Lambert; Altered Levels of Dopamine Metabolites and Vasoactive Intestinal Peptide (VIP) in Retinas of Aphakic Monkey Eyes . Invest. Ophthalmol. Vis. Sci. 2002;43(13):206.
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Purpose: Form deprivation during infancy induces excessive ocular elongation and myopia, associated with decreased dopamine metabolism and increased VIP levels in the retina. In contrast, neonatal aphakia causes stunted eye growth. The present study was conducted to determine whether retinal dopamine metabolism and VIP levels are altered in association with aphakia. Methods: Lensectomy and vitrectomy were performed on the right eye of rhesus monkeys at approximately one week of age; the contralateral eye was unmanipulated. Axial eye length was monitored by A-scan ultrasonography. Animals were sacrificed at 1-2 months of age, after the axial length difference between the aphakic and unmanipulated eye reached at least 0.5mm. The levels of retinal dopamine and its metabolites were measured by HPLC-ED. The levels of VIP were measured by radioimmunoassay. Results: Prior to surgery, the mean axial length of the left and right eyes of the subjects was identical. Following lensectomy, the aphakic eyes elongated more slowly than the fellow, unmanipulated eyes and, when the study was terminated, the operated eyes were significantly shorter. Lensectomy had no significant effect on steady-state dopamine levels in either central or peripheral retina. However, the dopamine metabolites, DOPAC and HVA, were significantly elevated in the central retina of aphakic eyes. DOPAC and HVA levels in the peripheral retina were similar in unmanipulated and aphakic eyes. VIP levels were significantly reduced in central, but not peripheral retinas of aphakic eyes, when compared to the unmanipulated eyes. Conclusion: Lensectomy, which reduces axial eye growth, alters retinal dopamine metabolite and VIP levels. The direction of this alteration is opposite to that produced by form deprivation, which increases axial eye growth. The results are consistent with the hypothesis that dopamine and VIP are components of the retinal pathway that regulates postnatal ocular growth.
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