Hyperopia and loss of accommodation following ciliary muscle disinsertion in the cynomolgus monkey: physiologic and scanning electron microscopic studies.

Twenty-three cynomolgus monkeys underwent 360-degree disinsertion and retrodisplacement of the ciliary muscle in one eye. Ten to 12 weeks after unilateral disinsertion, resting refraction in the "disinserted" eyes was more hyperopic than in the opposite eyes by 1.12 +/- 0.21 (mean +/- S.E.M.) diopters (p less than 0.001). Accomodative responses to intramuscular pilocarpine (2 or 3 mg/kg) were 0.90 +/- 0.14 (mean +/- S.E.M.) diopters in the disinserted eyes and 13.88 +/- 0.79 diopters in the opposite eyes. The induced hyperopia and loss of accommodation in the disinserted eyes seemed permanent, persisting for at least 14 months in one monkey and 29 months in three monkeys tested periodically after disinsertion. By light microscopy, the ciliary muscle in the disinserted eyes appeared normal and was contracted by pilocarpine. Scanning electron microscopy of the accommodative apparatus revealed retrodisplacement of the ciliary muscle, ciliary processes, and zonular plexus in the disinserted eyes. Structural alterations in the zonular apparatus seemed insufficient to account for the physiological findings. Hyperopia and loss of accommodation following ciliary muscle retrodisplacement are consistent with a new theory of zonular action during accommodation.