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Refractive surgery offers alternative for some children with amblyopia
Larger randomized clinical trials are needed before refractive surgery can be deemed safe and effective in children, surgeon says.
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Refractive surgery may prove to be a safe and effective approach to treating pediatric anisometropia, but it cannot be considered the primary treatment until longer-term clinical studies are conducted, a review of studies to date suggests.
Evelyn A. Paysse, MD, presented a summary of refractive surgical treatment options for pediatric anisometropia and other vision problems during the Pediatric Subspecialty Day at the annual American Academy of Ophthalmology meeting in Chicago.
“The problem right now is that all studies to date have had small patient numbers, and we really can’t make any definite conclusion,” Dr. Paysse said. “I think that a large, multicenter, randomized clinical trial is needed with large patient numbers and a control group of standard therapy.”
Earlier intervention may result in better visual acuities in patients who are less visually mature, Dr. Paysse said, but it is necessary to be cautious when considering refractive surgery in young patients.
“Caution at this point is the most important word I can say about this because we know that the pediatric eye is not just a small adult eye,” she said. “It reacts differently to surgical interventions, such as corneal transplants, cataract surgery, IOLs, and the cornea after refractive surgery in children may respond differently as well over time.”
The uncertainties in pediatric refractive surgery include the amount of response to treatment in pediatric eyes and the possibility of corneal haze, she said.
“The effect on the growing eye is unclear,” Dr. Paysse said. “In our own study we now have about a 4-year follow-up, but when we first started doing this we were concerned that PRK could lead to more corneal haze than in adults.”
More complex
Refractive procedures in children are more complex than they are in adults, Dr. Paysse said. Centration is an issue because under general anesthesia the patient cannot fixate, she pointed out.
“First of all, there’s a problem of cooperation,” Dr. Paysse said. “Children don’t fixate well oftentimes, and they’re not cooperative to sit at the machine, so this often requires general anesthesia. The anesthetic inhalational agents can interfere with the laser so you have to take precautions for that, but they are definitely able to be controlled for.”
Age is an important factor in the decision to perform refractive surgery.
“From birth to 2 years of age the eye goes through remarkable power changes,” she said. “It loses about 20 D of power from corneal flattening and lens changes, and it reaches almost the adult level by 2 years of age,” Dr. Paysse said. “So probably 2 years of age would be the earliest that we should consider performing refractive surgery in children.”
Treating amblyopia
The most research to date on refractive surgery in children has been done in anisometropic amblyopia, Dr. Paysse said.
“We know that anisometropia of more than 4 D, if it goes uncorrected, will lead to amblyopia 100% of the time, and also that compliance decreases as anisometropia increases,” she said.
There is no consensus on the minimum degree of anisometropia at which surgery should be considered, she said.
“About 4 D is where we’ll probably be thinking about treating,” she said. “Conventional treatment with anisometropic amblyopia consists of spectacle or contact lens correction and forced use of the amblyopic eye. This is a seemingly simple strategy; however, it’s wrought with problems in anisometropic patients for various reasons.” Problems with conventional treatments can include aniseikonia, diplopia and the increased risk of microbial keratitis in contact lens users, she said.
Data on about 130 patients who have undergone excimer laser treatment for pediatric anisometropia have been published by various authors, Dr. Paysse said, and their reports show good refractive correction, mild to moderate acuity improvement and minimal complications.
Included in that 130 eyes are 11 that Dr. Paysse and colleagues have reported on as part of a prospective pilot study of PRK. Patients in the study, which now has 4 years of follow-up, are 11 children who had severe anisometropia at a mean age of 6 years. These patients, eight of whom were myopic and three hyperopic, were non-compliant with conventional therapies, Dr. Paysse said.
Mean preop refractive error was 10 D in the myopic group and almost 5 D in the hyperopic group, she said. One patient had a preop refraction of –21 D.
“Even so, the maximum treatment dose for the myopic group was 11.5 D,” Dr. Paysse said. “The reason we chose that was because there have been reports of increased haze with higher treatment doses in adults, and we didn’t want that to happen in our children.”
At 3 years’ follow-up, half of the myopic group and all of the hyperopic group were within 2 D of target refraction, she said.
“Our 3-year data show that we have stable, predictable refractive correction,” Dr. Paysse said. “The higher myopic patients responded more to our treatment dose than expected, which was helpful, and they are closer to emmetropia because of that.”
For Your Information:
- Evelyn A. Paysse, MD, can be reached at Baylor College of Medicine, Texas Children’s Hospital, 6621 Fannin, MC 640.00, Houston, TX 77030; 832-822-3230; fax: 713-796-8100; e-mail: epaysse@bcm.tmc.edu.
Reference:
- Paysse EA, Hamill MB, et al. Photorefractive keratectomy for pediatric anisometropia: safety and impact on refractive error, visual acuity and stereopsis. Am J Ophthalmol. 2004;138(1):70-78.
- Daniele Cruz is an OSN Staff Writer who covers all aspects of ophthalmology.