Unilateral ptosis and eye dominance.

We studied the relationship between eye dominance (Scobee test) and upper lid level (MRD) in 54 patients with unilateral ptosis or asymmetric bilateral ptosis (> or = 2 mm difference in MRD) using the phenylephrine test. A contralateral lid drop was measured in 12/54 patients after instillation of 2.5% phenylephrine in the more ptotic eye and occurred in both congenital (3) and acquired (9) ptosis cases. A contralateral lid drop was seen in 7/14 (50%) patients whose ptosis was greater in the dominant eye and in 5/40 (12.5%) patients whose ptosis was greater in the nondominant eye (p = .01). Contralateral lid drops > or = 1 mm were present in 7/54 patients, and 6/14 (43%) of them had greater ptosis on the dominant side and 1/40 (2.5%) on the non-dominant side (p = .001). There was no association between contralateral pseudoretraction and either visual acuity or severity of ptosis. These results suggest that levator muscle tone is influenced by eye dominance when ptosis is present. The preoperative evaluation of unilateral or asymmetrical bilateral ptosis cases should include the Scobee and phenylephrine tests to unmask contralateral upper lid pseudoretraction.