Ultrasound biomicroscopic study of anterior segment changes after phacoemulsification and foldable intraocular lens implantation.

Purpose: To report quantitative changes in the anterior segment configuration after clear corneal incision phacoemulsification and foldable intraocular lens (IOL) implantation by means of ultrasound biomicroscopy (UBM).
Design: Prospective, nonrandomized, comparative (self-controlled) trial.
Participants: Twenty-one eyes of 19 patients with senile or presenile cataracts and no other ocular illness.
Methods: Patients were examined with UBM before and 1 and 3 months after surgery. At each UBM examination, axial images of the anterior chamber and radial sections of the angle at the superior, lateral, inferior, and medial quadrants were obtained.
Main Outcome Measures: Central anterior chamber depth (ACD), iris-lens contact distance, iris-lens angle (ILA), angle opening distance at points 250 (AOD250) and 500 microm (AOD500) from the scleral spur, trabecular-iris angle (TIA), iris thickness 500 microm from the scleral spur (IT), trabecular-ciliary process distance (TCPD), iris-ciliary process distance (ICPD), iris-zonule distance, iris-sclera angle (ISA), and ciliary process-sclera angle (CPSA). After surgery, central anterior chamber depth was also measured from the cornea to the IOL (ACD) and from the cornea to the pupillary plane (ACD2). Each variable was measured twice in different days by the same observer.
Results: The variables IT, TCPD, ICPD, IZD, and CPSA did not significantly change after surgery (P > 0.01). Central anterior chamber depth increased approximately 30% after surgery (approximately 850 microm; P < 0.001), by both measurement methods used (ACD x ACD and ACD x ACD2). Anterior chamber angle significantly increased, by approximately 50% of the initial value, by the three measurement methods used: AOD250 (P <or= 0.002), AOD500 (P < 0.001), and TIA (P <or= 0.003). The ISA increased by approximately 10 degrees (30%) after surgery (P < 0.001). The ILCD and ILA did not exist after surgery, except in two eyes.
Conclusions: After phacoemulsification and foldable IOL implantation, UBM revealed that the iris diaphragm shifted backward, deepening the anterior chamber by approximately 850 microm and widening its angle by approximately 10 degrees. These findings may be of clinical significance in eyes with angle-closure glaucoma or with occludable angles.