Elsevier

Ophthalmology

Volume 109, Issue 5, May 2002, Pages 936-941
Ophthalmology

Article for CME Credit
A comparison of laser photocoagulation with cryotherapy for threshold retinopathy of prematurity at 10 years: part 2. Refractive outcome1 ,

https://doi.org/10.1016/S0161-6420(01)01015-6Get rights and content

Abstract

Objective

To compare the refractive outcome of eyes treated with cryotherapy for threshold retinopathy of prematurity (ROP) with eyes treated with laser photocoagulation.

Design

Extended follow-up of a randomized controlled clinical trial.

Participants

One hundred eighteen eyes from 66 patients were randomly assigned to receive either cryotherapy or laser photocoagulation for threshold ROP. Twenty-five patients (44 eyes treated) were available for follow-up examination 10 years later.

Intervention

Cycloplegic autorefraction or retinoscopy was performed. Immersion ultrasound biometry (A-scan) was also performed, and an autokeratometer was used for keratometry. If an A-scan could not be tolerated or the patient was not cooperative, a B-scan through-the-lid biometry was performed. Corneal thickness was measured using optical coherence tomography.

Main and secondary outcome measures

Refractive error. In addition, anterior chamber depth, lens thickness, and axial length were measured. Central corneal thickness measurements and keratometric readings were also obtained.

Result

Eyes treated with cryotherapy were significantly more myopic than those treated with laser photocoagulation. When comparing patients with bilateral treatment, the mean spherical equivalent (SE) of eyes treated with laser was −4.48 diopters (D) compared with a mean SE of −7.65 D for eyes treated with cryotherapy (n = 15 pairs of eyes, P = 0.019). Cryotherapy-treated eyes had a mean axial length of 21.7 mm versus 22.9 mm for laser-treated eyes (P = 0.024, n = 12 pairs of eyes). The anterior chamber depth and lens thickness averaged 2.86 mm and 4.33 mm, respectively, in the cryotherapy-treated eyes compared with 3.42 mm and 3.95 mm in the laser-treated eyes (P < 0.001, n = 12 pairs for both measurements). There were no statistical differences in anterior corneal curvature and central corneal thickness between the two treatment modalities. Crystalline lens power bore the strongest correlation to refractive outcomes in both laser-treated (r = 0.885, P < 0.001) and cryotherapy-treated eyes (r = 0.591, P = 0.026). Although keratometric readings were higher than normal values in these eyes, there was no correlation to the degree of myopia.

Conclusions

Laser-treated eyes were significantly less myopic than cyrotherapy-treated eyes. Lens power seemed to be the predominant factor contributing to the excess myopia.

Section snippets

Materials and methods

The study population and initial randomization and treatment intervention protocol are described in the preceding report.

Refraction

When considering only patients who had bilateral treatment and favorable outcomes, those treated with laser had a mean SE of −4.48 diopters (D) (standard error of the mean [SEM] = 1.2D), whereas cryotherapy-treated eyes had a mean SE of −7.65 D (SEM = 1.6), (P = 0.019, n = 15 pairs of eyes). However, when all eyes, including fellow eyes of blind or untreated eyes were considered, mean SE for laser-treated eyes was −4.56 D (SEM = 1.1 D) and mean SE for cryotherapy-treated eyes was −7.41 D (SEM =

Discussion

In our previous report,6 we noted that eyes treated with laser photocoagulation had less myopia compared with eyes treated with cryotherapy. The goal of the current phase of this study was to determine the refraction of each of these patients approximately 10 years after treatment, with specific attention to the role of the cornea, AC depth, and axial length of the eye.

After 10 years of follow-up, the laser-treated eyes were significantly less myopic than their cryotherapy-treated counterparts,

Acknowledgements

The authors thank Andrew Smith, PhD, for his extensive statistical assistance with this article.

References (17)

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Cited by (0)

Supported by an unrestricted grant from Research to Prevent Blindness, New York, New York, and by a grant from Iridex Corporation, Mountain View, California.

1

None of the authors has any financial or proprietary interest in any of the techniques or equipment discussed in this article.

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