“…Sample size estimates were calculated with two formulas [ 12 , 13 ] for the dichotomous outcome and one [ 14 ] for the continuous outcomes, using previously published population estimates for the main outcome severe Meibomian gland atrophy [ 15 , 16 ], and for the secondary outcomes tear lipid layer thickness [ 16 , 17 ], non-invasive tear breakup time [ 17 , 18 ], fluorescein tear breakup time [ 17 – 19 ], and SPEED score [ 17 , 20 ]. The highest sample size estimate for the main outcome of severe Meibomian gland atrophy, derived from the formula by Peduzzi, et al [ 12 ], and from population estimates of severe Meibomian gland atrophy by Napoli, et al [ 15 ], was 55 subjects in order to detect 3:1 odds of having severe Meibomian gland atrophy with 5% two-sided level of significance and 80% statistical power. The highest estimate among all outcomes was for fluorescein tear breakup time using the formula from Charan, et al [ 14 ] and population estimates from Yeh, et al [ 18 ] suggesting a sample size of 101 subjects to detect a minimum of a five-second difference in tear breakup time with 5% two-sided level of significance and 80% statistical power.…”