By administering daily injections of Myanol a muscle relaxing agent containing a component 3-ortho-toloxy-1. 2-prorandiol, consecutively for 5 days to 40 patients with mild myopia under -3.0D (diopter), the author pursued what effects such injections would exert on the faculty of vision, the degree of myopia, and the accommodative enlargement of Mariotte's blind spot. 1. By the Myanol injection the faculty of vision has been markedly improved, showing in 59.2 per cent of the patients regaining the faculty of vision over 0.5 and in 27.6 per cent of them meked effect of restoring the faculty well over 1.0. 2. Most of mild myopia have been alleviated, and in 27.0 per cent the faculty of vision has been completely restored. The average refraction before the Myanol injections was -1.595D and it was brought down to -0.814D after the injection, 3. Myanol has a striking effect on myopia under -1.5D, but it demonstrates no effect on those above -1.75D. 4. As for the size of blind spot the Myanol inaection diminishes it mrkedly, and this seems to be due to the adjustment of spasmodic characteristics of Brucke's muscle. 5. By the Myanol injection the residual enlargement of blind spot and consensual enlargement in slight myopia are markedly diminished, lowering the residnal rate of the blind spot enlargement. This phenomenon appears to be due to the fact that the tension of Brucke's muscle is relaxed and thereby the muscle function is adjusted to its normalcy. 6. The fact that the degree of myopia is diminished and the faculty of vision is improved by adjusting the tension or dysfunctino of Bruck's muscle give a supporting evidence to Koyama's theory that myopia is caused by the dysfunction of Brucke's muscle.