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Five-year results in one cohort show CK effect regressed in hyperopes
A subset of patients enrolled in an FDA study experienced regression by 5 years.
Mean spherical equivalent regressed significantly at 5 years follow-up after conductive keratoplasty in hyperopic patients using the conventional CK technique, according to long-term results in one cohort of patients in a multicenter clinical trial.
Jason S. Ehrlich, MD, PhD, spoke about long-term results with CK for hyperopia at the American Society of Cataract and Refractive Surgery annual meeting in San Francisco.
He discussed the results in the Stanford University cohort of the multicenter clinical trial for Food and Drug Administration premarket approval of CK with the ViewPoint CK system from Refractec. The multicenter study, the results of which were published in 2002 in Ophthalmology, included 355 eyes at 13 centers. At 1 year, results from the trial were “very promising,” Dr. Ehrlich said during his presentation. The FDA-approved labeling of CK calls CK a temporary procedure, with treatment of presbyopia lasting 1 to 3 years.
Uncorrected visual acuity was better than 20/40 in 92% of patients, with a mean manifest refraction spherical equivalent within ±1 D of emmetropia in 90% of patients. About 90% of patients were within ±1 D of the intended refraction of plano.
However, when a smaller cohort of the study was examined by Stanford University researchers at 24 months postop, the mean spherical equivalent was 0.48 D, signifying a mean regression of 0.29 D toward the mean preoperative refraction of 1.6 D, he said. At 5 years, the mean refraction in patients still available for follow-up demonstrated further regression, Dr. Erlich said.
These results suggest that while CK appears to safe, it also appears to be effective only initially, Dr. Erlich said. Patients should be informed of the possibility of regression, he said.
“The treatment seems to regress significantly toward the preoperative baseline refraction over long periods of study, so probably patients should be counseled that the CK effect may be temporary,” Dr. Ehrlich said.
Stanford cohort results
The prospective Stanford University study looked at surgeries performed by a single surgeon. The university enrolled 25 eyes of 14 patients in the initial multicenter study. Mean age of the patients was 55.5 years.
“We subsequently have been following the Stanford cohort since the FDA study,” Dr. Ehrlich said. “This is the longest long-term follow-up for CK that we’re aware of, at least in the U.S. The goal of the current study was to evaluate the long-term safety, efficacy and stability of CK in mild to moderate hyperopia.”
Patients in the cohort had ±0.25 D of sphere and ±0.25 D of cylinder with no retreatment, he said. At 24 months post-op, 18 of the original 25 eyes were still included in the follow-up data.
At that time, 64% of those tested had 20/20 or better uncorrected visual acuity; 95% had 20/40 or better uncorrected visual acuity, Dr. Ehrlich said.
The latest data that Dr. Ehrlich and colleagues have collected is for 11 eyes of seven patients with an average of 55 months follow-up, nearly 5 years, with a range of 35 to 75 months. The preop characteristics of those 11 eyes were similar to the original study group as a whole, Dr. Ehrlich said.
The mean preop spherical equivalent was 1.47 D; at 24 months, it was 0.57 D, he said, which was similar to the 0.48 of the original cohort as a whole.
“As we get out to 60 months, there’s a significant regression toward the preop spherical equivalent refraction,” he said.
Regarding safety, Dr. Ehrlich said 27% of the 11 patients at the last follow-up were seeing 20/20 or better uncorrected and 64% were seeing 20/30 or better. One eye had developed a significant cataract, which is not surprising considering the cohort’s age group, Dr. Ehrlich said. The mean cylinder was more than ±0.25 D, he said.
Cohort limitations
Dr. Ehrlich said the long-term study in this cohort had limitations. It included only one surgeon at one center. Another limitation was the relatively small number of patients in the cohort, which grew smaller with each follow-up, he said.
The study also did not include patients treated with the more recently introduced LightTouch CK technique, he said. In addition, results were not stratified by preop central or peripheral corneal thickness. This could significantly influence treatment results, Dr. Ehrlich said.
“We do have that data, so we’re going to go back and look at that,” he said.
For more information:
- Jason S. Ehrlich, MD, PhD, can be reached at Stanford University, School of Medicine, Department of Ophthalmology, 300 Pasteur Drive, Room A157, Stanford, CA 94305-5308; 650-387-5714; e-mail: jehrlich@stanford.edu.
- Refractec, maker of the ViewPoint CK system, can be reached at 3 Jenner, Suite 140, Irvine, CA 92618; Web site: www.refractec.com.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.