Effect of a nitric oxide synthase inhibitor on lens-induced myopia.
OBJECTIVE
It has still not been determined whether the retinal mechanism causing form-deprivation myopia (FDM) is different from that causing lens-induced myopia (LIM). We previously reported that FDM was blocked by an intravitreal injection of the nitric oxide (NO) synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME). In this study, we investigated the effect of L-NAME on LIM in chicks.


METHODS
The left eyes of 6-day-old chicks were injected with 30 microl of nontoxic concentrations of L-NAME (< or = 360 mM) or saline. The right eyes were injected with 30 microl of saline. A -16 dpt lens was placed in front of the left eye for 6 days. Another group of 6 chicks were injected with 180 mM L-NAME (left eye) and with saline (right 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 by electroretinography 60 min after an intravitreal injection in non-LIM-treated eyes.


RESULTS
The eyes of chicks that were injected with 180 or 360 mM 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.


CONCLUSIONS
The injection of L-NAME into developing 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.
Fujikado
T
T
Department of Applied Medical Engineering, Osaka University Graduate School of Medicine, Osaka, Japan.
Tsujikawa
K
K
Tamura
M
M
Hosohata
J
J
Kawasaki
Y
Y
Tano
Y
Y
D000818:Animals; D002645:Chickens; D003261:Contact Lenses / Q000009:adverse effects*; D004596:Electroretinography; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007267:Injections; D009216:Myopia / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D012029:Refraction, Ocular; D012160:Retina / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester