Lens offers good results for high myopic correction

March 1, 2006

The anterior chamber width is one of the most important parameters when selecting patients for implantation of the anterior chamber phakic IOL.

The Vivarte IOL has an optic that is 5.5 mm in diameter, an overall diameter of 12, 12.5, or 13 mm, depending on the model, and a refractive index of 1.47. The IOL, which was specially designed for patients with high myopia, can correct from –7.0 to –25 D in 0.5-D increments. The soft optic and the haptics are made of hydrophilic acrylic.

Dr. Piovella, director of Centro de Microchirugia Ambulatoriale, Monza, Italy, underscored the importance of patient selection. All patients in this study had a minimal anterior chamber depth of 3.2 mm, an endothelial cell count greater than 2,500/mm2, were less than 50 years of age, and had an open angle, no angle hyperpigmentation, and no vessels in the angle in order to avoid a decentered pupil.

Precise white-to-white preoperative measurement must be done using the IOL Master (Carl Zeiss Meditec). This ensures that eyes that are out of range of the IOL size are identified. The white-to-white measurement can range from 11 to 12.50 mm, 1 mm added for the surgical limbus or the white-to-white can be 10.50 to 12 mm, with 0.5 mm added for clear cornea. Acceptable anterior chamber widths range from 11.50 to 13 mm.

Different size lenses

The width of the anterior chamber will determine which Vivarte IOL can be implanted: the Vivarte 120 with anterior chamber depths from 11.5 to 12 mm, the Vivarte 125 with depths from 12.1 to 12.5 mm, and the Vivarte 130 for depths from 12.6 to 13 mm. Dr. Piovella advised a final check of the intraoperative measurement using a surgical sizer.

He and his colleagues conducted a study in which 34 eyes of 20 patients were included. The mean patient age was 34.8 ± 7.6 years. The mean best preoperative spectacle-corrected visual acuity was 0.7 ± 0.3; the mean spherical equivalent (SE) was –15 ± 3.7 D; the preoperative IOP was 13.2 ± 3 mm Hg. The mean white-to-white measurement was 12.3 ± 0.3 mm and the mean endothelial cell count was 2,655 ± 396 cells/mm2.

Dr. Piovella described his surgical technique. Topical anesthesia was applied to all eyes preoperatively. A temporal incision was made in 26 eyes and a superior incision in eight eyes; all incisions were 2.5 mm. The viscoelastic Healon GV (Pfizer) was used. A final white-to-white measurement was done with the internal sizer. The incision was enlarged at the time of IOL implantation to 3.75 mm. No iridectomy was performed; the iris protects the lens during Vivarte implantation. The final step was irrigation/aspiration for viscoelastic removal.

Dr. Piovella reported that the mean implantable contact lens power was –15.00 ± 3.7 D (range: –9 to –22 D). Twenty-seven eyes (79%) received the Vivarte 125, four (12%) received the Vivarte 130, and three (9%) received the Vivarte 120. The mean anterior chamber width measured with the surgical sizer was 12.3 ± 0.3 mm.