Myasthenia gravis (MG) is a neuromuscular disorder that affects skeletal muscles, in particular, the extraocular muscles. Response variability is a hallmark sign. Detailed findings are described in a patient with MG in which the presenting sign was accommodative insufficiency. Objective accommodative findings were recorded 3 years before the onset of myasthenia, soon after the initial diagnosis was made, and then after the treatment commenced with pyridostigmine. In addition, clinical measurements were obtained periodically at different times of the day for various binocular motor functions, including near point of convergence, phoria, fusional and accommodative amplitudes, and relative accommodation. The disease adversely affected all accommodative and vergence findings, with fatigue being the primary disturbance. The therapeutic administration of pyridostigmine improved static measurements of accommodation and vergence and reduced asthenopia. The objective dynamic measurements of accommodation, vergence, and versions were less affected. These findings provide a clear demonstration that both intrinsic and extrinsic ocular muscles may be affected in the prepresbyopic myasthenic patient.