Bifocal control of myopia.

Forty-three native American bifocal wearers grouped by yearly age levels from 9 to 15 with a mixed group of 6 to 8 year olds are matched on beginning age, sex, beginning refractive error and ending age with 83 Native American control subjects. Similarly 226 Caucasian bifocal wearers are matched on the same criteria against 192 control subjects. Although the comparisons are made on each age group, the average annual rate of progression for the bifocal Native American subjects is -0.12 and -0.10 diopters in the right and left eyes respectively against a comparable rate of progression of -0.38 and -0.36 diopters for the control subjects. These differences are significant but not as significant as those found on the Causcasian subjects of -0.02 and -0.03 diopters right and left eyes against -0.53 and -0.52 diopters for the controls.