Percent Reduction from Tmax: What must we do before determining the percent reduction?

• A. Obtain a single post-treatment IOP
• B. Obtain multiple untreated IOP measurements
• C. Record office hours of testing
• D. Assess optic nerve head only

Answer: (B)

The essential step is to establish a reliable baseline Tmax from untreated IOP readings. IOP fluctuates with time of day and across visits, so a single pre-treatment measurement might not capture the true maximum. By taking several untreated measurements, you get a stable Tmax to use as the reference. Once Tmax is known, you calculate percent reduction after treatment as (Tmax − post-treatment IOP) ÷ Tmax × 100%. This baseline is what lets you quantify how much the IOP has truly fallen. Recording office hours or just assessing the optic nerve head don’t provide the necessary numerical baseline, and a lone post-treatment reading can’t define reduction from Tmax.