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Sally A McFadden; L-Arginine inhibits myopia in the mammalian eye. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2278.
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Ocular growth is regulated by the sign of imposed defocus and likely involves amacrine cells. We have previously reported that one particular class of amacrine cell changes its expression of nNOS in a bidirectional manner, being upregulated in myopic eyes, and down regulated in hyperopic eyes in the guinea pig retina. We manipulated the expression of nNOS by administering L-arginine and show here that myopia was also inhibited.
Two groups of guinea pigs (n=20) were raised with a -6D lens on one eye from 5-12 days of age and twice daily were administered eye drops containing either 0.9% Saline or 1.7% L-Arginine (LA). Drops were given 1 hr after lights on and 6 hrs later in the middle of their day cycle. Lenses were removed during the drop administration which occurred under dim red light or in darkness. At 12 days of age, animals were cyclopleged and refractive error measured. Eye length was subsequently measured in anaesthetised animals using high frequency ultrasound.
At the end of lens wear period, the mean refractive error in untreated eyes did not differ between the two groups (LA: +5.2 ± 0.5 D; Saline: +5.1 ± 0.8 D, p = .88). Significant relative myopia developed in 10/10 animals given saline eye drops sufficient to compensate for the -6D of imposed defocus (Saline: -6.7 ± 0.5 D, p = 0.000). In contrast, 7/10 animals administered LA eye drops did not develop myopia in the lens-wearing eye and the relative myopia in these 7 animals (LA: -2.5 ± 0.7 D) or the mean across all 10 animals (LA: -3.6 ± 0.8 D) was significantly less than that in the saline treated animals (p = .000 and p = .007 respectively). The myopia induced by -6D lens wear was caused by a longer eye. Control eyes given saline eye grew by 115 ± 18 µm; while in animals given LA, the mean growth in ocular length was only 42 ± 17 µm. This reduction in ocular growth caused by LA was highly significant (p = .01), and no relative growth occurred in the 70% of animals which failed to develop myopia.
LA eye drops protect the eye from developing myopia in 70% of animals, where the mean myopia was 37% of that in control animals, and completely eliminated the excessive growth normally associated with myopia.
This is a 2021 ARVO Annual Meeting abstract.
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