Patients with Y patterns (pseudo-overaction of the inferior oblique muscle) have normal ocular alignment in primary position and downgaze, but the eyes diverge in upgaze. These patients appear to have overacting inferior oblique muscles, but the deviation is thought to be due to anomalous innervation of the lateral rectus muscles in upgaze. Clinical characteristics that help identify this form of strabismus include the following: the overelevation is not seen when the eyes are moved directly horizontally, but it becomes manifest when the eyes are directed horizontally and slightly into upgaze; there is no fundus torsion; there is no difference in vertical deviation with head tilts; and there is no superior oblique muscle underaction.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.