B

Reasoning: For a normally distributed variable, about 95 % of individual values lie within ±2 standard deviations of the mean. With a mean IOP of 30 mm Hg and SD of 1 mm Hg, the lower 95 % limit is 30 – 2 × 1 = 28 mm Hg [Streiner, 1996, PMID 8899234].