Toric ICL promising for high myopia with astigmatism

March 15, 2005

San Diego—With data available from up to 1 year of follow-up in an ongoing FDA multicenter clinical trial, the toric ICL (STAAR Surgical) is demonstrating favorable efficacy, safety, and predictability for the correction of myopic astigmatism, said Capt. Steven C. Schallhorn, MD.

"We are seeing phenomenal clinical outcomes, exceptional accuracy in both the sphere and cylinder correction considering the high levels of myopia and cylinder treated, stability that is achieved early and maintained, and no immediate safety issues so far," reported Dr. Schallhorn, director, cornea and refractive surgery, Naval Medical Center, San Diego.

The analyses were based on 133 eyes of 96 patients; 61 eyes were seen at the 6-month visit and 18 eyes were seen after 12 months. Patients eligible for the study had between –3 and –20 D of myopia with between –1 and –4 D of cylinder. Surgery was performed on fellow eyes at least 6 weeks after the implant was placed in the first eye.

"The standard deviation of the MSE was also less than 0.5 D at all times, which further demonstrates the excellent predictability of the refractive outcomes," Dr. Schallhorn said.

The uncorrected visual acuity (UCVA) analyses showed that about 90% of eyes achieved UCVA of 20/20 or better. The efficacy analysis showed average postoperative UCVA was slightly better than the preoperative best spectacle-corrected visual acuity (BSCVA).

"These are phenomenal results for a single procedure for high myopia, and the efficacy outcomes are a testament to how well the emmetropia was targeted and how well the cylinder was corrected," Dr. Schallhorn commented.

Stringent criteria were used to assess refractive stability up to 6 months-the last timepoint for which sufficient data are available. Those analyses showed refractive results were stable at 1 week and were maintained thereafter.

The cylinder analyses revealed about 90% of eyes had ≤1 D of residual cylinder. In addition, there was excellent correlation between intended cylinder correction and vector-achieved cylinder (R2 = 0.85), indicating the implant performed well in correcting lower and higher levels of cylinder.

Assessments of the stability of the cylinder axis indicated that the lens does not appear to be rotating over time. In almost all eyes, the cylinder axis shifted <15° between 3 and 6 months, and only about 3% of eyes had a >30° shift in their cylinder correction.

"Surgeons use an alignment process and are very careful in positioning the lens intraoperatively. However, if it rotates, the cylinder power will be altered and that is a potential complication," Dr. Schallhorn said.

Patients on average achieved a 1-line gain in BSCVA beginning at 1 week, which was slightly greater than what would be expected from a minification effect alone. From 1 month onward, there were no patients with a >1-line loss from preoperative BSCVA.

Other safety data showed no eyes with inflammation persisting beyond the 1-month visit, an IOP increase from baseline >10 mm Hg, corneal decompensation, or corneal edema. A small anterior subcapsular cataract developed in a single eye, but it has remained stable and the patient's UCVA is 20/20.

Dr. Schallhorn also compared the results from toric ICL implantation with those achieved in a LASIK study performed at his center, and he concluded that the toric ICL appears better than conventional LASIK for the treatment of high myopia with astigmatism.

The patient populations in the two studies were well matched for age, although the mean preoperative myopia was about 1 D more in the toric ICL cohort.