Effect of a nitric oxide synthase inhibitor on lens-induced myopia

Purpose: It has still not been determined whether the retinal mechanism cau sing form-deprivation myopia (FDM) is different from that causing lens-indu ced myopia (LIM). We previously reported that FDM was blocked by an intravi treal injection of the nitric oxide (NO) synthase inhibitor, N-nitro-L-argi nine methyl ester (L-NAME), In this study, we investigated the effect of L- NAME on LIM in chicks. Method: The left eyes of B-day-old chicks were injec ted with 30 mul of nontoxic concentrations of L-NAME (less than or equal to 360 mM) or saline. The right eyes were injected with 30 mul of saline. A - 16 dpt lens was placed in front of the left eye for 6 days. Another group o f 6 chicks were injected with 180 mM L-NAME (left eye) and with saline (rig ht eye) before placing -16 dpt lenses in front of both eyes. After removing the lens, the refraction and the axial length were measured. The effect of L-NAME (180 mM) on the retina of a separate group of chicks was examined b y electroretinography 60 min after an intravitreal injection in non-LlM-tre ated eyes. Results: The eyes of chicks that were injected with 180 or 360 m M L-NAME were less myopic and had significantly shorter axial lengths than control eyes. A significant decrease of the On response and an increase of the Off response were observed. Conclusion: The injection of L-NAME into de veloping chick eyes that were then covered with a -16 dpt lens resulted in a modifications of retinal function and an inhibition of the development of myopia. These results, combined with the earlier findings, suggest that NO modulates a common retinal pathway that leads to both LIM and FDM. Copyrig ht (C) 2001 S, Karger AG, Basel.