麻豆传媒

CHICAGO -- Posterior chamber phakic intraocular lens (IOL) implantation safely and predictably improves visual acuity over 5 years in patients with high myopia or high myopic astigmatism who are not candidates for LASIK, photorefractive keratectomy or PRK.

A retrospective observational case series with the use of an implantable collamer lens (ICL) demonstrated satisfactory refractory outcomes, with most patients achieving 20/40 or better vision without the use of glasses or contact lenses, and good predictability at evaluation 5 years postoperatively in carefully selected patients, said from Iran University in Tehran. The ICL is highly biocompatible, allowing transmission of gases and nutrients.

He presented the 5-year follow-up data at the 2016 meeting.

"This study shows that if we have a complete preoperative evaluation and choose the right patient and the right lenses, and use proper surgical method and postoperative care, this technique is safe, predictable, and effective for this type of refractive error," he said.

Phakic ICL procedures were introduced to address the unsuitability of patients with high myopia or high astigmatism for laser vision correction. A phakic IOL implanted between the cornea and lens has several theoretical advantages, said Hashemian, including immediately stable vision, the ability for the IOL to be removed or exchanged, easy adjustment with complementary fine-tuning corneal surgeries, and high predictability. It also allows the crystalline lens to retain its function and may improve the natural properties of the optical system to enhance the quality of the retinal image.

All patients undergoing the phakic ICL procedure at the University of Tehran undergo extensive eye examination to determine candidacy, Hashemian emphasized. "We have to have a complete anterior segment analysis to choose the patients for this procedure," he said. The examination includes refractive measurements, standard slit-lamp exploration of the anterior segment, careful examination of the fundus under complete mydriasis, topography, endothelioscopy, applanation tonometry, ultrasound central corneal pachymetry and ultrasound biomicroscopy, among others.

Some of the patients eligible for phakic ICL are those with myopia > -6.0 D to -8.0 D, hyperopia >=4.0 D, myopic astigmatism (cylinder > -1.0 D), post-corneal grafts, post intra-corneal segment implantation, and pseudophakia (as a piggy-back lens).

Sixty eyes of 31 high myopic patients who had an ICL or toric ICL have been followed for 5 years following the procedure. The mean age of the patients at the time of surgery was 26.8 years. Criteria for inclusion were:

• Age 20 to 45 years
• Stable manifest refraction (0.50 D 6 months apart)
• Ametropia not correctable with excimer laser surgery
• Unsatisfactory vision with (or intolerance to) contact lenses or glasses
• An endothelium to anterior crystalline central distance >2.8 mm
• Irido-corneal angle aperture >30˚
• Endothelial cell count >2,500 cells/mm2 at 20 years of age and >2,000 cells/mm2 at 40 years of age
• No ocular pathology
• No previous ocular surgery

Five years postoperatively, the mean spherical equivalent was -1.53 D, a change from -11.74 D preoperatively, and the mean cylinder was -0.82 D, a decrease from -2.35 D preoperatively. Mean Snellen decimal corrected visual acuity increased from 0.58 preoperatively to 0.76 at 5 years postoperatively, and the mean uncorrected visual acuity changed from <0.1 to 0.61. Some 56.7% of eyes achieved 20/40 or better uncorrected visual acuity.

Sixty percent of eyes had 20/40 or better acuity with correction prior to surgery, which improved to 80% after the procedure.

Twenty percent of patients achieved corrected visual acuity of 20/120 to 20/50 that could be attributed to underlying retinal problems. But these patients still had better vision after surgery compared with before surgery, said Hashemian.

"In addition, astigmatism decreased significantly to nearly clinically insignificant values," he said.

The safety of the procedure is exemplified by the small declines in endothelial cell count, he said. Endothelial cell count decreased from 2,698 cells/mm2 at baseline to 2,514 cells/mm2 at 1 year and to 2,418 cells/mm2 at 5 years. The amount of endothelial cell loss has been reduced since the introduction of a newer design of phakic lens in 2014, Hashemian indicated. Realignment of the toric ICL was necessary in two eyes. No patient experienced cataract or glaucoma over the 5 years of follow-up.