Experimental study of different intraocular lens designs implanted in the bag after capsulorhexis

Abstract

Objective: To analyze experimentally in cadaver eyes several models of commercially available posterior chamber intraocular lenses (IOLs) to determine their stability, fixation, and behavior in the capsular bag in relation to their overall size, optic diameter, shape, material, and haptic configuration.Setting: Eye Bank and Department of Ophthalmology, University General Hospital of Alicante, Spain.Methods: Thirty-three IOLs of different sizes, shapes, and designs, divided in two series and five groups, were implanted successively in 31 cadaver eyes. All the proceedings were videotaped, and measurements were made on the television screen with the picture static. Main outcome measures were the diameters of the lens, the empty capsular bag, and the capsulorhexis; capsular distension by the IOL haptics; extent of haptic arc of contact with the capsular equator; and IOL mobility in the bag.Results: The stability of and stretching caused by the IOLs varied greatly depending on their overall size, haptic flexibility, and the extent of the arc of haptic contact with the capsular equator. Lenses between 13.5 and 14.0 mm had good stability but stretched the capsule excessively. The J-loop haptic configuration produced a spindle-shaped bag deformity that might come in contact with the ciliary processes in the physiologic eye. Among IOLs designed for in-the-bag implantation after capsulorhexis, the two smaller than 12.0 mm were unstable, permitting excessive mobility in the capsular bag. Except for IOLs with a 5.0 mm optic, all 12.0 mm IOLs had reasonable stability, little or no mobility within the capsular bag, and good short-term centering. Lenses with a broad angulation at the haptic-optic junction, to about 90 degrees, achieved the largest arc of contact with the equator and behaved as lenses with larger optics. The Pharmacia 808 performed best.Conclusion: After capsulorhexis and extracapsular cataract extraction, 12.0 mm, poly(methyl methacrylate), one-piece IOLs with modified C-shaped loops, 90 degree angulation at the haptic-optic junction, and an optic diameter between 6.0 and 6.5 mm performed best in the capsular bag.