Tyr mutation results in increased IOP and altered diurnal changes A. Different cohorts of C57BL/6J mice that are homozygous for the spontaneous Tyrc-2J mutation have higher IOP than their normal counterparts at all tested ages. All groups consisted of male and female mice. B. IOP is not increased during the dark period of the day in Tyrc-2J homozygotes. The number of mice analyzed during the light period were: 2 month, 28 +/+, 29 c-2J/c-2J, 4 month, 20 +/+ and 20 c-2J/c-2J, 8 month, 15 +/+ and 15 c-2J/c-2J. Fourteen mice of each genotype were successfully analyzed during the dark period of the day.