The effect of cataract extraction on the contractility of ciliary muscle.

PURPOSE To evaluate the changes in the pilocarpine-induced contractility of the ciliary muscle in eyes with presbyopia before and after cataract extraction using ultrasound biomicroscopy (UBM). DESIGN Prospective interventional case series. METHODS A clear corneal phacoemulsification and posterior chamber intraocular lens (AcrySof SA60AT; Alcon Laboratories, Fort Worth, Texas, USA) was implanted in 23 eyes in 15 subjects. UBM was performed with and without instilling 2% pilocarpine, as well as before and two months after cataract extraction. The mean (+/- standard deviation) age was 65.33 +/- 6.09 years (range, 56 to 75 years). The increase in the axial length of the ciliary body (CBAXL) was used as a surrogate indicator of the centripetal ciliary muscle contraction during accommodation. Images of the ciliary body were compared visually using Adobe Photoshop 7.0 (Adobe Systems Inc., San Jose, California, USA). RESULTS The CBAXL value with and without pilocarpine before cataract extraction was 1.708 +/- 0.165 mm and 1.689 +/- 0.187 mm, respectively, which was not significantly different (P = .261). The CBAXL value with and without pilocarpine after cataract extraction was 1.998 +/- 0.375 mm and 1.675 +/- 0.279 mm, respectively, which was significantly different (P < .001). The visually compared configurations of the changes in the ciliary body were compatible with the analysis of the measured parameters. CONCLUSIONS Pilocarpine induced only subtle movement of the ciliary body before cataract surgery. However, after cataract extraction, it induced significant centripetal movement of the ciliary body compared with that without pilocarpine. This shows that a lenticular sclerotic component may influence both lens movement and the contractility of the ciliary muscle, and is believed to be related to the presbyopia.