CLINICAL SCIENCES Development of Astigmatism and Anisometropia in Preterm Children During the First 10 Years of Life A Population-Based Study Eva K. Larsson, MD, PhD; Gerd E. Holmstro¨m, MD, PhD Objective: To assess the development of astigmatism 1 D or more at 21⁄2 years of age and cryotreated severe and anisometropia to 10 years of age in preterm chil- retinopathy of prematurity were risk factors for astigma- dren, previously included in a population-based study tism at 10 years of age, and that anisometropia of2Dor on the incidence of retinopathy of prematurity. more at 21⁄2 years of age was a risk factor for anisome- tropia at 10 years of age. Methods: Cycloplegic retinoscopies were performed in 198 preterm children at 6 months, 21⁄2 years, and 10 years Conclusions: The development of astigmatism and an- of age. We analyzed the development of astigmatism of isometropia showed a similar course, regardless of stage 1 diopter (D) or more and anisometropia of1Dormore. of retinopathy of prematurity. The retinoscopy findings at 6 months of age were of no value in predicting astig- Results: The amount and prevalence of astigmatism de- matism and anisometropia at 10 years of age, but the re- clined between 6 months and 21⁄2 years of age and then fraction at 21⁄2 years of age was. Retinoscopy at about 21⁄2 remained stable. We found no difference in the course years of age in all preterm children may be useful for de- of astigmatism at different ages with regard to stage of tecting astigmatism and anisometropia that will persist retinopathy of prematurity. The amount of anisometro- in children of school age. pia increased, but its prevalence remained unchanged. Multiple regression analyses showed that astigmatism of Arch Ophthalmol. 2006;124:1608-1614 PHTHALMOLOGICAL STUD- The aim of the present study was to as- ies of preterm (prema- sess the development of astigmatism and turely born) children anisometropia in this preterm cohort dur- have resulted in recom- ing the first 10 years of life and to deter- mendations that they mine whether it was related to the stage need follow-up examinations, to find those of ROP. We also wished to discuss which O 1,2 in need of extra help. However, such fol- children should be included in a pro- low-up programs are expensive and must gram to follow up refractive errors. be based on accurate knowledge of the prevalences of ophthalmological disor- METHODS ders in preterm and full-term children. Only a few population-based studies of A previous study by Holmstro¨m et al10 prospec- children from birth to school age have been tively determined the incidence of ROP in pre- performed in which the children have also term children in Stockholm County. The study been screened for retinopathy of prema- was population based and included 260 chil- turity (ROP) in the neonatal period.3-7 The dren with a birth weight of 1500 g or less, which results reveal a higher prevalence of re- was the inclusion criterion. The infants had ges- fractive errors in preterm than in full- tational ages at birth of 24 to 35 weeks. One hun- term children. dred five children (40.4%) had ROP, and 28 In Stockholm County, Sweden, a co- (10.8%) had received cryotherapy. The crite- hort of preterm children (born September rion for treatment was stage 3 ROP in at least 4 1, 1988, through October 31, 1990) that contiguous clock hours in zone II, even in the absence of plus disease. All children who ful- was screened prospectively for ROP was fol- filled this criterion were treated.10 Author Affiliations: lowed up with retinoscopies at 6 months, Two hundred forty-eight of the preterm chil- 7,8 Department of Ophthalmology, 21⁄2 years, and 10 years of age. The de- dren were followed up ophthalmologically for Uppsala University Hospital, velopment of spherical equivalent refrac- 3.5 years,8,11 and 216 of them were asked to re- Uppsala, Sweden. tive error has recently been reported.9 turn at 10 years of age.7,12 The dropouts have (REPRINTED) ARCH OPHTHALMOL / VOL 124, NOV 2006 WWW.ARCHOPHTHALMOL.COM 1608 ©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 Table 1. Demographic Data of 198 Preterm Children by ROP Group* Severe ROP Characteristic Total Group No ROP Mild ROP Untreated Cryotreated No. of RE/LE 198/197 121/123 42/36 12/14 23/24 No. with data for most severe ROP 118 41 15 24 No. M/F 94/104 57/61 21/20 7/8 9/15 Gestational age, mean (SD), wk† 29.1 (2.3) 29.8 (2.3) 28.3 (1.8) 28.3 (1.9) 27.5 (2.2) Birth weight, mean (SD), g† 1162 (221) 1212 (206) 1136 (233) 1121 (192) 988 (200) Abbreviations: LE, left eye; RE, right eye; ROP, retinopathy of prematurity. *Data are presented as number of children, unless otherwise indicated. †Data are according to the eye with the most severe stage of ROP. carefully been described elsewhere.7-9,11,12 Retinoscopies during ASTIGMATISM cycloplegia were performed at 6 months, 21⁄2 years, and 10 years 7,8 of age using cycloplegic eyedrops. Of the 216 preterm chil- In the entire preterm group, the median value of astig- dren, 198 were examined on all 3 occasions and are included in matism declined between 6 months (1.0 D) and 21⁄2 years the present study. Ͻ Retinopathy of prematurity was classified as none, mild of age (0.5 D) (P .001), but remained stable thereafter (stages 1-2), or severe (stages 3-5). Severe ROP was further sub- (0.5 D). divided into untreated and cryotreated severe ROP. The prevalences of astigmatism of1Dormore at 6 Astigmatism was recorded as a negative cylinder and de- months, 21⁄2 years, and 10 years are illustrated in fined as significant at 1 diopter (D) or more and as high at 2 D Figure 1. In the entire group, the prevalence fell sig- Ն or more. The axes of astigmatism ( 1 D) were divided into with- nificantly between 6 months and 21⁄2 years of age (PϽ.001) the-rule astigmatism (0°-15° and 165°-180°), against-the-rule and then became stable (P=.6). Although no change in astigmatism (75°-105°), and oblique astigmatism (16°-74° and 1 the prevalence occurred between 2 ⁄2 and 10 years of age, 106°-164°). Right and left eyes underwent separate evalua- 27 children lost their astigmatism, and 14 new cases were tions. Anisometropia was defined as significant when the dif- Ն ference in spherical equivalent between the eyes was1Dormore seen. The prevalences of astigmatism ( 1 D) declined and as high if the difference was 2 D or more. When anisome- slightly in the children with no ROP and mild ROP be- 1 tropia was assessed, the preterm group was divided into no, mild, tween the examinations at 2 ⁄2 years and those at 10 years severe untreated, and severe cryotreated ROP according to their of age, but in the children with cryotreated severe ROP most severely affected eye. the prevalence increased during this period. However, The study was approved by the local ethics committee at these differences were not statistically significant. Karolinska Institutet, Stockholm, Sweden. Informed consent The axes of astigmatism (Ն1 D) at the 3 examina- was received from the families. tions are given in Table 2. In 21 children, astigmatism (Ն1 D) was present on all 3 retinoscopies. Nineteen of STATISTICAL METHODS them had against-the-rule or oblique astigmatism, and no statistically significant change in their axis of astig- The Wilcoxon matched-pair signed rank test and the t test for matism over time was proved (P=.8). dependent samples were used to compare astigmatism in the right In the stepwise logistic multiple regression analysis of and left eyes. We used the Friedman test to analyze the median astigmatism (Ն1 D) at 10 years of age, we included as values of astigmatism and anisometropia as well as the axis of astig- independent risk factors the gestational age at birth, matism over time (at 6 months, 21⁄2 years, and 10 years of age). In the analysis of the prevalence of astigmatism on serial exami- birth weight, stage of ROP (including cryotreated severe nations, we performed an analysis of variance for repeated mea- ROP), and astigmatism of1Dormore at 6 months and sures (the GENMOD Procedure in SAS; SAS Institute Inc, Cary, 21⁄2 years of age. In the univariate analyses, all of the risk NC). We performed stepwise logistic regression analyses (com- factors were significant. However, in the multiple regres- bining backward elimination and forward selection methods) sion analysis, only cryotreated severe ROP and the pres- to determine the most important risk factors for astigmatism ence of astigmatism at 21⁄2 years of age were indepen- (Ն1 D) and anisometropia (Ն1 D) at 10 years of age. dent risk factors for astigmatism at 10 years of age (Table 3). RESULTS We calculated the sensitivity and specificity for vari- ous cutoff points of astigmatism at 21⁄2 years of age for There was no statistically significant difference between astigmatism of1Dormore at 10 years of age (Table 4). the right and left eyes in the analyses of astigmatism. De- tails concerning the 198 right eyes are given below. In ANISOMETROPIA the analyses of anisometropia, 197 children were in- cluded because retinoscopy could not be performed in The median value of anisometropia in the entire pre- the left eye of 1 child at the 21⁄2-year examination.