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This article was reviewed by Donny Won Suh, MD
Results from the Hyperopia Treatment Study 1 (HTS1) have proven to be inconclusive after three years of follow-up in young children with moderate hyperopia treated with glasses compared with observation. A small-to-moderate benefit or no benefit of immediate glasses was seen compared with observation.
The study rationale was that 4% to 14% of children have moderate to high levels of hyperopia, a scenario that carries a significantly increased risk for development of strabismus and amblyopia. Based on previous studies, it is controversial whether glasses should be prescribed immediately for children with moderate myopia to prevent amblyopia and strabismus from developing.
The alternative is observation until signs of decompensation become apparent followed by prescribing of glasses, according to Donny Won Suh, MD, chief of pediatric ophthalmology, University of Nebraska Ophthalmology, Children’s Hospital and Medical Center, Omaha.
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Dr. Suh and Marjean Kulp, MD, were protocol chairpersons of the HTS1 that sought to determine the visual acuity (VA) and alignment benefits, if any, of immediate eyeglass prescription compared with observation for children from 1 to less than 3 years of age who had +3.0 to +6.0 D of hyperopia after a follow-up period of three years.
The 106 study patients with anisometropia and mild astigmatism and no apparent strabismus were randomly selected to either having eyeglasses prescribed immediately or observation and followed every six months for three years. During follow-up, if decompensation became apparent in the observation group, glasses and other appropriate treatments were prescribed.
Criteria included decreased distance VA, decreased stereoacuity, and heterotropia. During follow-up, investigators were alert to any signs of permanent damage.
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Failure versus deterioration
Failure was not the same as deterioration, Dr. Suh noted. Failure was defined at the end of the study and had to be confirmed both in and out of refractive correction to answer the question about whether harm had been done by waiting to prescribe glasses or other treatments. On the other hand, deterioration could have occurred at any follow-up examination before the end of the study and defined in randomized treatment.
The criteria to define deterioration were as follows during unmasked testing in randomly selected correction and confirmed during retesting by a masked examiner:
> Measurable heterotropia;
> Presence of a VA or stereopsis below age-normal values in patients 3 and older,
> Significant, or marked parental concern.
When deterioration was identified, cycloplegic refraction was performed and new glasses were prescribed if patients were under observation. For patients randomly selected for eyeglasses, a full cycloplegic refraction was performed to determine if the esotropia improved. The patients then were released to receive care that included patching, atropine, and/or surgery and followed.
In the primary study, failure was defined as harming the VA, stereoacuity, or alignment, in the presence of the following with/without trial frames and then confirmed by a masked test and retest: measurable heterotropia, VA and stereoacuity below age-normal values, or a previous strabismus surgery, Dr. Suh explained.
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Dr. Suh reported that 34% and 21% of patients, respectively, failed in the observation group and the glasses group, a difference of -13% (95% confidence interval, -31%-4%).
“The results mean that if the study was repeated in a similar population, the difference can be up to 31% and in favor of eyeglasses,” he said. “However, the other extreme was also possible, with 4% in favor of observation. There was no significant difference in the failure rate at three years between the two groups.”
Patients who failed at three years did so because of failure of stereoacuity. Failure occurred in 30% in the observation group and 10% in the glasses group. The results for strabismus and VA were similar.
When patients were analyzed by different degrees of hyperopia, +2.5 to <+4.0 D, +4.0-+5.0 D, and >+5.0-+6.07 D, a greater difference was seen in the low hyperopia group, with about 30% failing observation and about 10% failing glasses, Dr. Suh noted.
Regarding deterioration before three years, 33% deteriorated in the glasses group and 58% in the observation group. “This was the expected finding before the study,” he said.
The reasons for deterioration were similar to those for failure, with the observation group having greater deterioration than the glasses group.
Analysis on the effect on emmetropization at three years showed that the patients in the observation group had a very slight nonsignificant decrease in hyperopia, 0.16 D.
The first key take-home point was that 58% of the observation group met the criteria for deterioration, in that they required glasses. About 50% had been followed for three years without signs of deterioration in VA, stereopsis, and strabismus.
The second take-home point showed that the failure rates in the two groups did not differ significantly, but there was a 13% difference favoring glasses.
“For children who are from 1 to 3 years of age with uncorrected moderate hyperopia (+3 to +6 D spherical equivalent), our estimates of failure after three years of every six-month follow-up did not allow definitive recommendations,” Dr. Suh concluded. “However, the results were consistent with a small-to-moderate benefit or no benefit of immediate glasses compared with careful observation, with glasses if deterioration occurs. Further studies are needed to answer the question.”
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Donny Won Suh, MD
Dr. Suh has no financial interest in this technology. This study was sponsored by the National Eye Institute.