NEI Clinical Studies
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Correction of Myopia Evaluation Trial (COMET)
- To evaluate whether progressive addition lenses (PALs) slow the rate of progression of juvenile-onset myopia (nearsightedness) when compared with single vision lenses, as measured by cycloplegic autorefraction. An additional outcome measure is axial length, as measured by A-scan ultrasonography.
- To describe the natural history of juvenile-onset myopia in a group of children receiving conventional treatment (single vision lenses).
Myopia (nearsightedness) is an important public health problem, which entails substantial societal and personal costs. It is highly prevalent in our society and even more frequent in Asian countries; furthermore, its prevalence may be increasing over time. High myopia contributes to significant loss of vision and blindness. At present, the mechanisms involved in the etiology of myopia are unclear, and there is no way to prevent the condition. Current methods of correction require lifelong use of lenses or surgical treatment, which is expensive and may lead to complications. The rationale for this trial, the Correction of Myopia Evaluation Trial (COMET), arises from the convergence of research involving (1) the link between accommodation and myopia in children and (2) animal models of myopia showing the important role of the visual environment in eye growth. A contribution of this research is that blur is a critical component in the development of myopia. The primary aim of COMET, to evaluate the efficacy of progressive addition lenses, a noninvasive intervention, in slowing the progression of myopia, follows from this line of reasoning. These lenses should provide clear visual input over a range of viewing distances without focusing effort by the child. The comparison of myopia progression in children treated with PALs versus single vision lenses will allow the quantification of the effect of PALs on myopia progression during the followup period.
The COMET is a multicenter, randomized, double-masked clinical trial to evaluate whether PALs slow the progression of juvenile-onset myopia as compared with single vision lenses. The study is a collaborative effort that involves a Study Chair at the New England College of Optometry; four clinical centers at colleges of optometry in Boston, Birmingham, Philadelphia, and Houston; and a Coordinating Center at the State University of New York at Stony Brook.
The sample size goal, 450 children with myopia in both eyes who met specific inclusion and exclusion criteria, was attained with the enrollment of 469 children in one year. Children were identified from school screenings, clinic records, and referrals from local practitioners. Eligible children were randomly assigned to receive progressive addition or single vision lenses. Participating children are being examined at 6-month intervals following baseline, for at least 3 years, to measure changes in refractive error and to update prescriptions, according to a specified protocol. A dilated examination to evaluate the study outcome measures is performed at the annual study visits. A standardized, common protocol is used at all centers.
The primary outcome of the study is progression of myopia, defined as the magnitude of the change relative to baseline in spherical equivalent refraction, determined by cycloplegic autorefraction. The secondary outcome of the study is axial length measured by A-scan ultrasonography.
Children between the ages of 6 and 12 years with myopia in both eyes (defined as spherical equivalent between -1.25 D and -4.50 D in each eye as measured by cycloplegic autorefraction), astigmatism less than or equal to 1.50 D, and no anisometropia (defined as a difference in spherical equivalent between the two eyes greater than 1.0 D) were eligible for inclusion. Exclusion criteria included visual acuity greater than 20/25, strabismus, use of contact lenses, birth weight less than 1,250 grams, use of bifocal or progressive addition lenses, or any conditions precluding adherence to the protocol.
Patient Recruitment Status
Completed. Child recruitment began in September 1997 and was completed in September 1998.
Current Status of Study
The mean age of the 469 COMET children at baseline is 9.3 years (range 6-11 years); 52 percent are female. This group of children is ethnically diverse, according to a self-report, with 46 percent white, 26 percent African-American, 14 percent Hispanic, and 8 percent Asian. Mean residual accommodation measured twenty minutes after instillation of two drops of tropicamide (1 percent) was found to be small (0.38D in the right eye and 0.30D in the left eye). Thus, tropicamide (1 percent) is an effective cycloplegic agent in myopic children. Baseline mean (± sd) cycloplegic refractive correction in COMET children is -2.38 D (± 0.81) in the right eye and -2.40 D (± 0.82) in the left eye. Young children have significantly less myopia than older children, but the amount of myopia does not differ by gender or ethnicity. Mean axial dimensions are: 4.0 ± 0.2 mm (anterior chamber), 3.4 ± 0.2 mm (lens), 16.8 ± 0.7 mm (vitreous chamber), and 24.1 ± 0.7 mm (axial length). Girls have significantly shorter eyes than boys. Mean corneal radii are 7.73 mm (horizontal) and 7.59 mm (vertical). Ninety-five percent of the children have a ratio of axial length to corneal radius greater than 3.0. These baseline measures provide cross-sectional data on a large group of ethnically diverse myopic children and will serve as a basis for examining changes that occur over a minimum of three years of follow-up.
Use of PALs compared with SVLs slowed the progression of myopia in COMET children by a small, statistically significant amount only during the first year. The size of the treatment effect remained similar and significant for the next 2 years. The results provide some support for the COMET rationale—that is, a role for defocus in progression of myopia.
The small magnitude of the effect does not warrant a change in clinical practice.
Gwiazda J, Marsh-Tootle W, Hyman L, Norton T, and the COMET group: Baseline refractive and ocular component measures of children enrolled in the Correction of Myopia Evaluation Trial (COMET). Invest Ophthalmol Vis Sci, in press.
Gwiazda J, Hyman L, Hussein M, Everett D, Norton TT, Kurtz D, Leske MC, Manny R, Marsh-Tootle W, Scheiman M, and the COMET Group: A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. Invest Ophthalmol Vis Sci 44: 1492-1500, 2003.
Hyman L, Gwiazda J, Marsh-Tootle W, Norton T, and the COMET Group: The Correction of Myopia Evaluation Trial (COMET): Design and baseline characteristics. Controlled Clinical Trials 22: 573-592, 2001.
Manny R, Hussein M, Scheiman M, Kurtz D, Nieman K, Zinzer K, and the COMET Study Group: Tropicamide (1%): An effective cycloplegic agent for myopic children. Invest Ophthalmol Vis Sci 42: 1728-1735, 2001.
Jane Gwiazda, Ph.D.
New England College of Optometry
424 Beacon Street
Boston, MA 02115
Telephone: (617) 236-6234
Fax: (617) 369-0188
Leslie Hyman, Ph.D.
M. Cristina Leske, M.D., M.P.H.
Division of Epidemiology
Department of Preventive Medicine
University Medical Center
Stony Brook, NY 11794-8036
Telephone: (516) 444-7525
Donald Everett, M.A.
National Eye Institute
National Institutes of Health
Executive Plaza South, Suite 350
6120 Executive Boulevard MSC 7164
Bethesda, MD 20892-7164
Telephone: (301) 496-5983
Fax: (301) 402-0528
Last Updated: 3/25/2003