Abstract:
Background and Purpose: A- and V-patterns are commonly encountered with cyclovertical muscle palsies. Inferior oblique (IO) muscle palsy produces an Apattern caused mainly by the decreasing abducting action of the IO in upgaze and an increasing abducting action of the superior oblique in downgaze. V-pattern association with an IO palsy has not been, to our knowledge, reported before. The purpose of our paper is to report a patient with IO palsy and a paradoxical Vpattern and explain the proposed pathophysiology behind the V-pattern. Case Report: We report a 67 year-old female with a 3 year history of diplopia. She met the Bielschowsky-Parks' three-step test to identify an IO muscle palsy, and she showed all the usual criteria of an IO muscle palsy except for a paradoxical V-pattern. Conclusion: Many forces affect patterns in cyclovertical muscle palsies. A Vpattern in IO palsy can be explained by the spread of comitance resulting in inhibitional innervational pseudo-palsy of the superior rectus muscle resulting in V-exotropia or in inhibitional palsy of the contralateral superior oblique muscle resulting in V-esotropia. © Strabology Quarterly.