Anterior segment changes during accommodation in eyes with a monofocal intraocular lens: high-frequency ultrasound study

PURPOSE: To analyze anterior segment structure changes during accommodative stimuli after monofocal intraocular lens (IOL) implantation using 2 ultrasound biomicroscopy (UBM) systems. SETTING: Department of Ophthalmology, University of Verona, Verona, Italy. METHODS: Twenty-six eyes (23 patients) with 1 of 4 monofocal IOL types were studied. Five to 9 months postoperatively, the patients were examined by high-frequency UBM using the HiScan system (Optikon 2000 SpA) and UBM 840 system (Carl Zeiss Meditec). Anterior chamber depth (ACD), iris-zonule distance, anterior chamber angle (ACA), scleral-ciliary process angle, and iris-ciliary process angle were measured using both systems. The iris-ciliary process distance and scleral spur perpendicular-sulcus distance were measured with the UBM 840 system and the sulcus-sulcus distance and capsular bag-IOL position with respect to ciliary process apex, with the HiScan system. Two experienced examiners performed all measurements. RESULTS: All parameters except the horizontal iris-ciliary process distance and vertical ACA measured by the UBM 840 system and horizontal ACA by the HiScan system showed significant variation during accommodation. An anterior shift of the IOL-capsular bag ciliary processes--sulcus-zonular iris complex was observed. A simultaneous centripetal shift of ciliary bodies and processes, shown by a reduction in sulcus and capsular bag diameter, was also observed. CONCLUSION: Anterior segment structures demonstrated accommodative movement on UBM after implantation of standard monofocal IOLs.