Ultrasound biomicroscopic changes during accommodation in eyes with accommodating intraocular lenses: pilot study and hypothesis for the mechanism of accommodation

PURPOSE: To document ciliary body constriction and movement with the Crystalens AT-45 intraocular lens (IOL) (eyeonics) using ultrasound biomicroscopy.SETTING: Eye Clinic, Department of Neurological and Visual Sciences, University of Verona, Verona, Italy.METHODS: Patients with no preexisting ocular conditions other than cataract who agreed to return for follow-up were considered. Twenty eyes of 14 patients with a best corrected visual acuity of 5/10 or worse and a refractive error (spherical equivalent) of +/-1.0 diopter (D) had implantation of a Crystalens AT-45 accommodating IOL. Six patients had bilateral implantation. Ultrasound biomicroscopy was performed postoperatively at 1 and 6 months. Before and during accommodation, the anterior chamber depth (ACD) was measured to assess the endothelium-IOL distance and measure the scleral-ciliary process angle to determine whether there was anterior rotation of the ciliary body. The uncorrected distance acuity, best corrected distance acuity, uncorrected near acuity, distance corrected near acuity, best corrected near acuity, and accommodative amplitude were determined. Analysis was done to determine whether there was a correlation between the accommodative amplitude and the percentage variation in the ACD and scleral-ciliary process angle.RESULTS: All surgical procedures were uneventful. The mean uncorrected distance acuity at 1 month was 0.8 +/- 0.14 (SD) and remained stable at 6 months. Three of 20 eyes (15%) and 8 of 20 eyes (40%) had a Jaeger acuity of J1 and J3, respectively, without additional power correction. During accommodation, the mean reduction in ACD was 0.32 +/- 0.16 mm at 1 month and 0.33 +/- 0.25 mm at 6 months. The mean narrowing of the scleral-ciliary process angle was 4.32 +/- 1.87 degrees at 1 month and 4.43 +/- 1.85 degrees at 6 months. There was a correlation between accommodative amplitude and a decrease in the ACD (r=0.404) and a decrease in scleral-ciliary process angle (r=0.773).CONCLUSIONS: Anterior displacement of the Crystalens IOL and corresponding anterior rotation of the ciliary body occurred during near vision. The IOL displacement and rotation were proportional to the accommodation capacity.