Elsevier

Ophthalmology

Volume 108, Issue 2, February 2001, Pages 343-347
Ophthalmology

Does cryotherapy affect refractive error?: Results from treated versus control eyes in the cryotherapy for retinopathy of prematurity trial1,

Presented in part at the annual meeting of The Association for Research in Vision and Ophthalmology, May 1998, Fort Lauderdale, Florida.
https://doi.org/10.1016/S0161-6420(00)00527-3Get rights and content

Abstract

Purpose

To evaluate the effect of cryotherapy on refractive error status between ages 3 months and 10 years in children with birth weights of less than 1251 g in whom severe retinopathy of prematurity (ROP) developed in one or both eyes during the neonatal period.

Participants

Two hundred ninety-one children in whom severe ROP developed during the neonatal period.

Intervention

Cryotherapy for ROP.

Main outcome measures

Cycloplegic Refraction

Methods

The children underwent repeated follow-up eye examinations, including cycloplegic retinoscopy, between 3 months and 10 years after term due date. Refractive error data from all eyes that were randomized to cryotherapy were compared with data from all eyes that were randomized to serve as controls. Refractive error data were also compared for a subset of children who had both a treated and a control eye that could be refracted.

Results

At all ages, the proportion of treated eyes that were unable to be refracted because of retinal detachment, media opacity, or pupillary miosis was approximately half the proportion of the control eyes that were unable to be refracted. When data from all eyes that could be refracted were considered, the distribution of refractive errors between fewer than 8 diopters (D) of myopia and more than 8 D of hyperopia was similar for treated and control eyes at all ages. The proportion of eyes with 8 D or more of myopia was much higher in treated than in control eyes at all ages after 3 months. In the subset of children who had a treated eye and a control eye that could be refracted, distributions of refractive errors in treated versus control eyes were similar at most ages.

Conclusions

In both treated and control eyes, there was an increase in the prevalence of high myopia between 3 and 12 months of age. Between 12 months and 10 years of age, there was little change in distribution of refractive error in treated or control eyes. The higher prevalence of myopia of 8 D or more in treated eyes, as compared with control eyes, may be the result of cryotherapy’s preservation of retinal structure in eyes that, in the absence of cryotherapy, would have progressed to retinal detachment.

Section snippets

Patients

The study population consisted of the 291 children who participated in the randomized trial of cryotherapy for ROP. All were born between January 1, 1986, and November 30, 1987, with birth weights less than 1251 g. During the neonatal period, 240 of the infants developed bilateral severe (threshold) ROP, defined as a minimum of five contiguous or eight cumulative clock hours of stage 3+ ROP in zone 1 or zone 2. In these infants, one eye was randomly assigned to undergo cryotherapy and the other

Spherical equivalent refractive errors

Figure 1 shows the distribution of spherical equivalent refractive errors for all treated (dark bars) and all control (hatched bars) eyes at the 10 test ages. At all ages, the proportion of eyes that could not be refracted is approximately twice as great in the control group as the treated group, as reported previously.11, 13 Among eyes that could be refracted at 3 months, the distribution of refractive errors in treated eyes was similar to that for control eyes. At all other test ages, the

Discussion

When evaluating any therapeutic method, the clinician must consider possible adverse results of the treatment. It has been suggested that cryotherapy increases the likelihood of high degrees of myopia in eyes with severe ROP.4 The comparison of refractive errors in all eyes that underwent cryotherapy and all eyes that served as controls is presented in this paper. Figure 1 indicates that, at all 10 follow-up ages, the distribution of refractive error in the range from less than 8 D of myopia to

References (16)

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    Wu and coworkers reported cataract formation in 1% of eyes following IVB injection for ROP.9 CRYO-ROP and ET-ROP trials and some other studies reported that myopia and high myopia increased significantly after ablation of peripheral retina for the treatment of ROP.23–27 Gelonek et al. compared the refractive outcomes following IVB injection and laser photocoagulation.28

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Supported by the National Eye Institute, Bethesda, Maryland (cooperative agreement no. U10 EY05874).

1

A listing of cooperative group participants can be found in Archives of Ophthalmology 1996;114:417–24.

2

Reprint requests to CRYO-ROP Study Headquarters, Oregon Health Sciences University, Department of Ophthalmology, L467, 3375 SW Terwilliger Boulevard, Portland, OR 97201-4197 (Earl A. Palmer, MD).

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