3-year CK outcomes for presbyopia show good refractive stability

No eyes lost lines of BCVA, and no significant astigmatism was induced

Issue: March 10, 2008

ByBob Kronemyer

A 3-year follow-up study of near-plano presbyopes who underwent conductive keratoplasty to decrease their dependence on reading glasses showed that the procedure provides refractive stability.

Jason E. Stahl

“As far as I know, this is the longest published outcomes,” study author Jason E. Stahl, MD, said. “Stability of the conductive keratoplasty procedure during the 3 years of followup was also more stable than I had anticipated.”

Dr. Stahl assessed not only the stability of the refractive error in the CK eye, but also the stability in the nontreated eye. “From the 1-year to the 3-year follow-up period, there was essentially a +0.18 D change in the nontreated eyes,” he told Ocular Surgery News. “This finding was not significantly different from the +0.25 D change that we observed in the CK-treated eyes during the same period.”

There is a natural hyperopic shift in this age group (mean age of study patients was 51 years) that has been reported in longitudinal population-based studies, he said.

“In our study, patients were still functioning well at near vision at 3 years but certainly not seeing as well as at 1 year,” Dr. Stahl said. “Still, the majority of patients were at J3 and functioning without glasses for most of their distance and near tasks.”

Data for nine patients

Ten patients (six women, four men) originally underwent the nonlaser, radiofrequency-based thermal keratoplasty procedure in one eye. However, one patient was lost to follow-up after the 1-year exam. “This patient has not responded to our request for him to come in,” Dr. Stahl said.

Dr. Stahl performed all of the procedures with the ViewPoint CK system (Refractec), and they represent his first 10 CK cases ever. “It is important to note that these procedures were performed with the original standard pressure technique,” he said.

The patients’ refractive stability was supported by keratometry readings. “There was no significant change in the mean keratometry from 1 year to 3 years,” Dr. Stahl said about the follow-up study, which appeared in the Journal of Refractive Surgery. “In other words, the steepening that we added with the CK procedure has not been lost. There has not been a relaxation, so to speak, of the collagen-shrinkage procedure.”

Preoperatively, the mean keratometry on videokeratography was 43.5 D, as opposed to 45 D at 1 year and 3 years. “This shows we are not getting a loss of the CK effect in the cornea,” he said.

Predictability also remained high. At 3 years postop, 100% of eyes were within ±1 D, 78% were within 0.75 D, 44% were within 0.5 D and 22% were within 0.25 D of the intended correction.

Two newer techniques

Since Dr. Stahl performed the CK procedure with the traditional pressure technique, two newer techniques have been developed: the light pressure technique, also known as a neutral pressure technique, and the template-guided technique, which is a throwback to the standard pressure technique. “Until there is a similar type of longitudinal study, we probably won’t know if these new techniques are better,” Dr. Stahl said.

He said he believes that the light pressure technique is easier to perform because the surgeon starts further out at the 7-mm optical zone rather than at the 6-mm treatment zone.

“Therefore, there is less possibility of inducing astigmatism,” he said. “However, because you have less pressure, I think you could end up with an overcorrection and more regression.”

The template approach also involves less pressure, but the Keratoplast tip is designed to penetrate deeper. “This would likely provide better long-term stability than the neutral pressure technique,” Dr. Stahl said.

Cylinder change minimal

Using the standard technique, no eyes lost lines of best corrected visual acuity at 1 and 3 years, and there was no significant induction of astigmatism. In addition, there was no significant change in cylinder. “The absolute change from preop to 1 year was 0.22 D, and at 3 years it was 0.06 D,” Dr. Stahl said. “No eye had an increase greater than 0.75 D in cylinder 3 years after surgery.”

One of the keys to successful CK is centration and properly centering it over the pupil. “Proper placement of the CK spots is also important,” he said. The template method can be helpful to less experienced surgeons by increasing the likelihood of perfect placement of every CK spot.

For more information:

Jason E. Stahl, MD, can be reached at 5520 College Blvd., Suite 201, Overland Park, KS 66211; 913-491-3330; fax: 913-491-9650; e-mail: jstahl@durrievision.com. Dr. Stahl has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.

Reference:

Stahl JE. Conductive keratoplasty for presbyopia: 3-year results. J Refract Surg. 2007;23:905-910.

Bob Kronemyer is an OSN Correspondent based in Elkhart, Ind.