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Researchers seek a way to control myopia progression in children
Clinicians faced with myopic children have focused on several treatment options, the most promising of which appear to be bifocal spectacles and rigid gas-permeable (RGP) contact lenses. However, experts say that because myopia affects such a large portion of the population, much more research in this area is needed.
“The best study that has been done so far in terms of bifocals and their ability to control myopia progression was George Fulk’s,” according to Karla Zadnik, OD, PhD, of The Ohio State University College of Optometry.
In Dr. Fulk’s study (Fulk GW, Cyert LA, Parker DE. A randomized trial of the effect of single-vision versus bifocal lenses on myopia progression in children with esophoria. Optometry and Vision Science. 2001;77(8)), 82 myopic children ages 8 to 11 years were randomized to either single-vision spectacles (40 children) or flat-top bifocals (42 children). This resulted in a 20% treatment effect over approximately 2.5 years, Dr. Zadnik said. “The average progression in the group that wore single-vision spectacles was 1.25 D. In the bifocal group, it was just less than 1 D,” she told Primary Care Optometry News.
COMET study
Dr. Zadnik also said that the COMET study, the Control of Myopia Evaluation Trial, is 2 years into the 3-year planned follow-up period. This trial is much larger and is funded by the National Eye Institute, as was Dr. Fulk’s work. “We will have to wait and see, but the federal funding brings with it a certain rigor in the conduct of the studies that we haven’t had in the field for a long time,” she said.
The children in the COMET study (more than 400) are randomized to either single-vision spectacles or progressive-addition lenses.
The CLAMP study
The Contact Lens and Myopia Progression Study (CLAMP) randomized children to either hard (RGP) or soft contact lenses. The lead investigator, Jeff Walline, OD, MS, is a senior research associate at The Ohio State University College of Optometry and a graduate student of Dr. Zadnik’s.
One year of follow-up has been completed in the 3-year study, which is looking at 116 children, ages 8 to 11 years. “In the past, one of the problems with all of the RGP lens studies has been that there’s a higher dropout rate in the contact lens group because the kids can’t get used to wearing them,” said Dr. Zadnik. “In the CLAMP study, everybody had to get accustomed to hard contact lenses before they were randomized to either hard or soft, so the dropout occurred before the children were assigned to their treatment group.”
Dr. Zadnik believes that this will make the results more valuable.
The Singapore Study
The pilot results of the Singapore study showed that myopia progression was suppressed in children wearing RGP lenses as compared to their spectacle-wearing counterparts. The authors reported in the Singapore Medical Journal that after 3 years of follow-up on about 100 of the 300 children in the study, the mean increase in myopia was 0.42 D in those wearing RGPs vs. 0.78 D in the spectacle-wearing children.
The final results from all 300 children with 2 D to 4 D of myopia are expected soon.
Inconclusive results
Dr. Walline told Primary Care Optometry News that, by and large, the results of bifocal studies are conflicting. “Some say they work, and some say they don’t, but the effect is never that large,” he said. “With single vision spectacle lenses, you expect kids to progress about 0.5 D per year, but we don’t see any prevention of myopia or considerable slowing of the progression with bifocal lenses.”
Dr. Zadnik said it is safe to say that bifocals and RGPs appear to show some promise with mild to moderate retardation of myopia progression. “We don’t know if they would actually be able to keep myopia from beginning,” she said. “It is really up to the community and patients and their parents to determine if the benefits outweigh the risk or the hassle. If you had to decide whether your child was going to wear bifocals and you knew it was only a 20% treatment effect, would that be worth it to you?”
Vision therapy
At the American Academy of Optometry meeting in Orlando in December 2000, Bill B. Rainey, OD, MS, and colleagues presented results of a longitudinal study designed to investigate the effects of vision therapy on myopia progression. Children with at least 0.50 D of myopia were randomly assigned to either vision therapy (VT) or control. Both groups received single-vision lenses with the manifest subjective refraction prescribed. Subjects in the VT group were evaluated every 2 months and were instructed to perform each of three different VT procedures daily for 3 weeks. Forty-one children (27 control, 14 VT) completed 1 year, and 34 children (24 control, 10 VT) completed 3 years.
Myopia progression rates were no different between the groups, nor did lag of accommodation change for either group. Researchers concluded that the accommodative and vergence VT procedures used in the study had no effect on progression rates or accommodative lag in myopic children.
“The results of the study were a bit disappointing, as we had hoped that VT would have some effect on slowing myopia progression,” Dr. Rainey said. “Further controlled study is definitely needed. However, for now, I would not be able to recommend VT as a treatment for myopia.”
He added that “anecdotal and empirical justifications for such use of VT clinically can only serve to provide more ammunition to those who choose to disparage and deprecate the use of VT for other, more appropriate diagnoses.”
Myopia acquired?
Cary Herzberg, OD, in private practice in Aurora, Ill., believes that most cases of myopia he sees today are acquired. He sees a direct correlation between higher myopia rates and several recent developments: the introduction of the soft contact lens and the use of computers.
“It used to be that people in their 20s and 30s never came in for eye check-ups after they got out of college, because their eyes didn’t change,” Dr. Herzberg said. “All of a sudden, I started seeing patients every 6 months for increases in prescriptions. So I asked myself what the common denominator was. The patients would tell me that they just got a new computer.”
According to Dr. Herzberg, the advent of the soft lens led to a dramatic decrease in doctors fitting hard lenses. “Hard lenses are effective for controlling myopia, but the soft lenses just don’t do that at all. So I think that these two events have had a huge impact on the progression of myopia as we see it today,” he said.
Stay tuned
Five years from now, Dr. Zadnik said, there will be more clinical studies on the control of myopia to help practitioners better advise their patients about the options.
“One of the things I tell people,” Dr. Zadnik said, “is to stay tuned, because this is a really active area of research right now, with a significant amount of government funding. What we find out in the next 5 years may alter how we practice. Optometrists take care of nearly 75% of the United States’ myopes. I think it’s something that everybody needs to stay on top of in terms of reading the results of these studies and understanding what they mean for our patients.”
For Your Information:
- Karla Zadnik, OD, PhD, can be reached at The Ohio State University College of Optometry, 338 West 10th Ave., Columbus, OH 43210; (614) 292-6603; fax: (614) 292-4705; e-mail: zadnik.4@osu.edu.
- Jeff Walline, OD, MS, is a senior research associate at The Ohio State University College of Optometry. He can be reached at 338 West 10th Ave., Columbus, OH 43210; (614) 292-6603; fax: (614) 292-4705; e-mail: walline.1@osu.edu.
- Bill B. Rainey, OD, MS, can be reached at the School of Optometry at Indiana University, 800 East Atwater Ave., Bloomington, IN 47405; (812) 855-8241; fax: (812) 855-7045; e-mail: brainey@indiana.edu.
- Cary Herzberg, OD, can be reached at 2956 Ogden Ave., Aurora, IL 65105; (630) 851-3338; fax: (630) 851-2740; e-mail: Drherz@aol.com.