Surgical correction of severe myopia with an angle-supported phakic intraocular lens

Purpose: To evaluate the effectiveness, predictability, and safety of a fou rth-generation angle-supported anterior chamber phakic intraocular lens (IO L) in patients with severe myopia. Setting: Refractive Surgery and Cornea Unit, Alicante Institute of Ophthalm ology, Miguel Hernandez University School of Medicine, Alicante, Spain. Methods: In this prospective study, 23 eyes (16 patients) with a mean preop erative myopia of -19.56 diopters (D) +/- 1.76 (SD) (range -16.75 to -23.25 D) were implanted with the ZSAL-4 phakic IOL. Basic examinations were perf ormed before and after surgery in all patients. Eighteen eyes were also stu died by clinical specular microscopy, and the endothelium was analyzed for cell density, coefficient of variation in cell size, and hexagonality. The location of the IOL in the anterior chamber was evaluated in 10 eyes by A-s can biometry. To evaluate haptic geometry, a theoretical mechanical model w as used. The follow-up was 24 months in ail patients. Results: Uncorrected visual acuity was 20/40 or better in 13 eyes (56.0%) 1 2 months after surgery and in 14 eyes (60.8%) at 24 months. Best spectacle- corrected visual acuity improved 0.19 at 12 and 24 months (0.1 = 1 line) fr om preoperative values. The efficacy index was 1.12 at 24 months and the sa fety index, 1.45. The mean postoperative spherical equivalent was -0.65 +/- 0.65 D at 24 months. The postoperative spherical equivalent was within +/- 1.00 D of emmetropia in 19 eyes (82.6%) at 12 and 24 months. The mean endot helial cell loss was 3.50% at 12 months and 4.18% at 24 months. The coeffic ient of variation in cell size decreased from 0.34 before surgery to 0.28 a t 24 months after surgery. The IOL was located 0.79 +/- 0.24 mm in front of the crystalline lens. Postoperative complications included night halos in 6 eyes (26.1%) at 12 and 24 months and pupil ovalization in 4 eyes (17.4%), Intraocular lens rotation was observed in 10 eyes (43.5%) at 24 months. Tw o eyes (8.7%) developed a slight inflammatory response during the first 6 m onths. Our mechanical model predicted that the compression forces against t he angle structures were greater at the first footplate than at the second. Conclusions: implantation of the ZSAL-4 IOL in the anterior chamber of phak ic eyes was effective and predictable in correcting severe myopia. However, the ZSAL-4 did not prevent pupil ovalization, IOL rotation, or low-grade p ostoperative uveitis. improvements in haptic design following our mechanica l model could decrease these haptic-related complications. (C) 2000 ASCRS a nd ESCRS.