Abstract
Purpose:
Recently, contact lenses for astigmatism have been developing for the contact lens users increased. 180°and 90°are the main axis in the contact lens for astigmatism, but there are no studies that analyze the demand for other astigmatic axis. So we undertook a thirteen and a half year large scale follow-up study of 120,000 eyes of Japanese patients who had a prescription for glasses to correct ametropia, analyzing the distribution of astigmatism axis according to spherical surface power and astigmatic power.
Methods:
The subject of this study are the 118,969 eyes of men and women (60,202 eyes of men; 58,767 eyes of women) in the age range 10 to 30, which have astigmatism and were prescribed glasses to correct ametropia at Okada eye clinic in Kanagawa, Japan from January 2001 to June 2014.
Results:
As a result of analysis, the most common axis found was 180° in 54,937 eyes (46.2%); the next most common was 90° in 17,288 eyes (14.5%); followed by 170° in 8,831 eyes (7.4%); 10° in 5,955 eyes (5.0%); and 160° in 3,624 eyes (3.1%). In this study, we divided the spherical surface power into 5 groups (High myopia (S < -6.00D); medium myopia (-6.00D < S < -3.00D); low myopia (-3.00D < S < -0.25D); emmetropia (-0.25D < S < +0.25D); hypermetropia (S > +0.25D)), and analyzed each group according to spherical surface power. The most common axis was 180° in every group, and as the myopia got stronger, the percentage with 180° got significantly higher (P<0.0001). The next most common axis was 170° in high myopia and medium myopia; and 90°in low myopia, emmetropia and hypermetropia. We also divided the astigmatic power into 5 groups and analyzed it according to astigmatic power. In every group 180° was the most common axis and next was, 170°in astigmatic power higher than -0.75D (C < -0.75D); and 90° in astigmatic power lower than -0.75D (C > -0.75D).
Conclusions:
As the result of this study, approximately 60% of the astigmatic axis were 180°or 90°. There other axis, 10°, 160°and 170°, occupy approximately 15% of the whole.<br /> In addition, it became clear that in the group in which spherical surface power is over S-3.00D or the astigmatic power is over C-0.75D, the demand for 170° axis is relatively high.