Accumulating data demonstrate favorable performance of toric ICL

Dr. Neuhann is director, AaM Augenklinik am Marienplatz, Munich, Germany. In 1999, he was the first surgeon worldwide to implant a TICL. The device obtained CE approval in Europe in 2003, was approved for marketing in Canada in June 2005, and is currently undergoing FDA review.

To date, more than 4,000 of the lenses have been implanted, and results from clinical trials and clinical practice experience show the TICL is associated with rapid return of excellent vision, accurate refractive results that are maintained from postoperative day 5 onward, and no serious complications when selected eyes undergo careful preoperative biometry to guide lens selection and to make sure they meet the anatomic criteria for implantation.

Cylindrical power correction

The TICL is a single-piece implant with a central concave/convex optical zone that varies in diameter from 4.65 to 5.50 mm across its entire spherical dioptric power range. It is available in half-diopter increments for both spherical power correction (range, –3.0 to –23.0 D) and cylindrical power correction (range, +1.0 to +6.0 D) The foldable implant can be placed through a 3.5-mm or smaller clear corneal incision.

Appropriate candidates for TICL implantation are patients ranging in age from 20 to 55 years with at least –3.0 D of myopia accompanied by 1.0 to 5.0 D of symmetrical corneal astigmatism. Eyes should have an anterior chamber depth of at least 2.8 mm (endothelium to anterior crystalline lens surface) and a minimum endothelial cell count of 2,000 cells/mm² . To avoid problems with halos, glare, regression, and secondary glaucoma, the scotopic pupil size should be smaller than the diameter of the TICL optic. TICL length is chosen based on the white-to-white (WTW) measurement, which should be between 11.0 and 13.0 mm. Available TICL lengths are 11.5, 12.0, 12.5, and 13.0 mm.

WTW measurement

"The WTW measurement was considered the most critical factor for proper sizing of this implant, but for years there were only topographers with objective WTW measurement available. Based on work presented by Dan Reinstein, MD, we know today that the sulcus to sulcus distance is not related to the WTW distance, and we and others are now using ultrasound biomicroscopy to measure the actual sulcus diameter for better TICL sizing," Dr. Neuhann said.

Lens power calculation was originally performed by the manufacturer using data submitted on subjective refraction, automated keratometry, and corneal topography. Beginning in 2002, an electronic calculation program became available that allows surgeons to perform power calculations for their own patients.

Dr. Neuhann reported outcomes for his own TICL series of 84 eyes with myopia ranging from –4.0 to –14.0 D and regular astigmatism between 1.5 and 8.0 D. In that cohort, for which mean follow-up is about 3 years, 92% of eyes have uncorrected visual acuity (UCVA) of 20/40 or better, no eyes have lost 2 or more lines of best spectacle-corrected visual acuity (BSCVA), while about 40% benefited with a 1- to 4-line gain in BSCVA.