Stereopsis in bilaterally pseudophakic patients

PURPOSE: To investigate the stereoacuity in patients who have had implantation of a monofocal intraocular lens (IOL) in each eye and to identify the principal risk factors for impaired stereoacuity. SETTING: Hayashi Eye Hospital, Fukuoka, Japan. METHODS: One hundred patients scheduled for bilateral phacoemulsification and monofocal IOL implantation were recruited. Near stereoacuity was measured approximately 2 weeks after surgery using the Titmus test. Various parameters that may be associated with stereoacuity in pseudophakic patients were measured using the New Aniseikonia Test (Handaya Corp.). Parameters included age, visual acuity, spherical equivalent, astigmatism, axial length, pupil diameters, IOL decentration and tilt, and aniseikonia. Stepwise multiple regression analysis was performed to identify independent predictors of impaired stereoacuity. RESULTS: The mean stereoacuity was 57.1 seconds of arc +/- 36.9 (SD); 90 patients (90%) had a good stereoacuity (ie, 100 seconds of arc or better). Simple regression analysis showed that a larger difference in spherical equivalent between fellow eyes and older age was significantly associated with poor stereoacuity. The best final model (R(2) = 0.375) in the multiple regression analysis identified a greater difference in spherical equivalent to be the most significant predictor of impaired stereoacuity, followed by older age and a larger pupil diameter. CONCLUSIONS: Ninety percent of patients with bilateral pseudophakia had useful stereoacuity. The main risk factor for poor stereoacuity was a greater difference in the spherical equivalent between the eyes, followed by older age and a larger pupil diameter. These results indicate the need for an accurate preoperative IOL power calculation.