A modified Müller's muscle-conjunctival resection procedure was performed to correct minimal to mild blepharoptosis with good levator function. A semilinear formula was used to excise specific amounts of Müller's muscle for different amounts of blepharoptosis. This formula was modified by less than adequate responses with the phenylephrine test. The phenylephrine test was also used to unmask contralateral ptosis so that bilateral surgery or less resection on the primarily ptotic eye could be planned. This modified technique and formula provides an approach to better quantitate minimal to mild ptosis surgery and yield more predictable results.