Los Angeles-Intracorneal ring segments (Intacs, Addition Technology Inc.) carry hope of success for patients with keratoconus, especially when the channels for the ring segments are created using the IntraLase femtosecond laser (IntraLase Corp.).
"The goal of implanting Intacs should be primarily to make patients who are con- tact lens intolerant contact lens tolerant and thus prevent a corneal transplant," said Yaron Rabinowitz, MD, director of ophthalmology research, Cedars-Sinai Medical Hospital, Los Angeles.
"A second goal is that the procedure may allow for transition from rigid to soft toric contact lenses and may allow for improved visual acuity with spectacles only," he continued.
Dr. Rabinowitz credits his interest in Intacs to a study reported in 2001 by Joseph Colin, MD, from Bordeaux, France.
In his first attempts at implanting Intacs using a mechanical technique, Dr. Rabinowitz reported that he was impressed with the results in the first 10 eyes.
"My results were very similar to those of Dr. Colin in that the uncorrected visual acuity (UCVA) improved three lines and the best-corrected visual acuity (BCVA) improved by 2.4 lines," he said.
The procedure improved even more for him when he began to do the implants using the IntraLase femtosecond laser to create the channels. He demonstrated how the laser creates the small circular ring in 8 seconds and the vertical cut in 4 seconds. The Intacs segments can then be implanted under the microscope very easily.
"This is a very simple procedure, once you learn a couple of tricks and master the learning curve," Dr. Rabinowitz stated.
He explained that the best measurement to use for the channel width is 0.4 mm.
"In fact, the narrower the channel is made, the more of an effect you get," he explained. For oval cones, he uses asymmetric Intacs (0.25 and 0.35 mm), for nipple cones symmetric Intacs (0.35 mm), and for mild cones just one Intacs segment.
The results reflect the improved technique.
The average UCVA improved 3.42 lines and the BCVA improved 3.35 lines, Dr. Rabinowitz explained.
"When I compared these results with those of the patients who underwent the mechanical procedure, in virtually all parameters the IntraLase group did better than the mechanical group," he reported.
Following the procedure, he reported that in the IntraLase group 85% of his patients achieved contact lens tolerance; two patients were not able to tolerate contact lenses and one patient developed an infection. In the mechanical group, 70% achieved contact lens tolerance, two patients underwent transplants because of fluctuating vision, and one ring segment was explanted because it was too shallow.
"The advantage of using the IntraLase laser compared with performing the procedure mechanically is that at 6 months following the procedure the UCVA and the BCVA are better than those in any study in the literature to date in which the mechanical procedure was done," Dr. Rabinowitz said. "Further follow-up is needed to determine if the 6-month data are comparable to the 12-month data. No explants of the Intacs were required. Finally, the depth of placement can always be guaranteed."
In addition to those advantages, the overall patient satisfaction was high in the IntraLase group. The time required to perform the procedure decreased from 20 minutes when done mechanically to 5 minutes when done with the IntraLase. There is less pain associated with the IntraLase procedure and quicker visual recovery.