Development of Astigmatism and Anisometropia in Preterm Children During the First 10 Years of Life a Population-Based Study

Home , Astigmatism, Retinopathy

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 anisometropia 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

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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 various 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 included 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. Table 1 term group showed no change between 6 months (0 D) shows the demographic characteristics and stage of ROP and 21⁄2 years of age (0 D), but increased between 21⁄2 in the 198 children. and 10 years of age (0.25 D) (PϽ.001).

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©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 A B C Total Study Group (N = 198) No ROP (n = 121) Mild ROP (n = 42) 100 100 100 ≥ 2 D ≥ 2 D ≥ 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D 80 80 80

60 60 60

12 35

Percentage 40 Percentage 40 17 Percentage 40 2

73 10 4 1 20 20 39 20 14 15 10 4 44 8 31 21 12 0 0 0 6 mo 2½ y 10 y 6 mo 2½ y 10 y 6 mo 2½ y 10 y Age Age Age

D E Untreated Severe ROP (n = 12) Cryotreated Severe ROP (n = 23) 100 100 ≥ 2 D ≥ 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D 80 80

60 9 60 6

Percentage 40 Percentage 40 3 11 9 20 20 7 1 2 1 0 0 6 mo 2½ y 10 y 6 mo 2½ y 10 y Age Age

Figure 1. Prevalences of astigmatism of 1 diopter (D) or more in the preterm cohort at 6 months, 21⁄2 years, and 10 years of age. ROP indicates retinopathy of prematurity.

Table 2. Axes of Astigmatism Ն1 Diopters at 6 Months, 2½ Years, and 10 Years of Age*

Severe ROP Axis of Astigmatism No by Age at Examination Total Group ROP Mild ROP Untreated Cryotreated 6 mo (n = 108) With the rule 13 (12) 8 (14) 2 (8) 1 (11) 2 (12) Against the rule 56 (52) 29 (52) 16 (62) 4 (44) 7 (41) Oblique 39 (36) 19 (34) 8 (31) 4 (44) 8 (47) 2½ y(n=54) With the rule 5 (9) 2 (8) 1 (6) 0 2 (20) Against the rule 28 (52) 16 (64) 7 (41) 2 (100) 3 (30) Oblique 21 (39) 7 (28) 9 (53) 0 5 (50) 10y(n=41) With the rule 8 (20) 3 (19) 2 (22) 0 3 (21) Against the rule 17 (41) 6 (38) 4 (44) 2 (100) 5 (36) Oblique 16 (39) 7 (44) 3 (33) 0 6 (43)

Abbreviation: ROP, retinopathy of prematurity. *Data are presented as number (percentage) of children.

The prevalences of anisometropia at 6 months, 21⁄2 cases and developed in others (Table 5). Therefore, of years, and 10 years of age are given in Figure 2. During the 8 children with ansiometropia of1Dormore and the study, the prevalence remained stable apart from in- less than2Dat6months of age, 7 no longer had it at dividual variations. Anisometropia disappeared in some 21⁄2 years of age. Of the 6 children with anisometropia

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©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 of1Dormoreandless than2Dat21⁄2 years, only 1 child was still anisometropic at 10 years of age. However, in Table 3. Results of Stepwise Multiple Regression Analysis Ն the 7 children with high anisometropia (Ն2D)at6 of Risk Factors for Astigmatism ( 1 D) at 10 Years of Age months of age, 6 continued to have high anisometropia (Ն2 D) during the study, and in the 11 children with high Risk Factor OR (95% CI) P Value Ͻ anisometropia at 21⁄2 years of age, 9 had anisometropia Cryotreatment 9.8 (3.2-30.3) .001 of2Dormore at 10 years of age. Astigmatism Ն1 and Ͻ1.5 D at age 2½ y 5.3 (2.0-14.1) Ͻ.001 Astigmatism Ն1.5 and Ͻ2Datage2½ y 23.7 (5.1-109.5) Ͻ.001 In a stepwise logistic multiple regression analysis of Astigmatism Ն2Datage2½ y 39.4 (6.9-224.6) Ͻ.001 anisometropia of1Dormore at 10 years of age, we included gestational age at birth, birth weight, the stage of Abbreviations: CI, confidence interval; D, diopter; OR, odds ratio. ROP (including cryotreated severe ROP), and anisometropia of1Dormore at 6 months and 21⁄2 years of age. In the univariate analyses, all of the risk factors were sta- Table 4. Sensitivity and Specificity of Thresholds tistically significant. However, in the multiple regres- of Refraction at 2½ Years of Age for Astigmatism (Ն1D) sion analysis, the presence of anisometropia of2Dormore at 10 Years of Age at 21⁄2 years of age (PϽ.001) was the only independent risk factor for anisometropia at 10 years of age (Table 6). Threshold of No. of Cases The sensitivity and specificity for detecting anisome- Astigmatism of Astigmatism tropia of1Dormore at 10 years of age at various thresh- at Age 2½ y, D Missed at (No. of Eyes) Sensitivity, % Specificity, % Age 10 y olds of anisometropia at 21⁄2 years of age are given in Table 7. Ն0.5 (126) 92.7 43.9 3 Ն0.75 (59) 75.6 82.1 10 Ն1 (54) 65.9 82.8 14 COMMENT Ն1.5 (21) 36.5 96.2 26 Ն2 (10) 19.5 98.7 33

In the present population-based study, we analyzed the de- Abbreviation: D, diopter. velopment of astigmatism and anisometropia in preterm children during their first 10 years of life. The amount and the prevalence of astigmatism were found to decrease be- unlike studies of normal children.22,23 The differences in tween 6 months and 21⁄2 years of age and remained stable the development of astigmatism between these 2 groups thereafter. The amount of anisometropia increased be- of children may be caused by an arrest in the normal pro- tween 21⁄2 and 10 years of age, but the prevalence was stable cess of emmetropization, ie, disturbances in ocular growth during the entire study, although there were individual such as changes in axial length, an increase in corneal cur- variations. No significant difference in the course of re- vature, a shallower anterior chamber, and a thicker lens, fractive development was detected for the various sub- which have been described in preterm children.6,16,24-26 groups of previous ROP. The presence of astigmatism and Dobson et al27 assert that it is important to detect astig- anisometropia at 21⁄2 years of age were the strongest risk matism at an early age and prescribe eyeglasses for pre- factors for having astigmatism and anisometropia at 10 years vention of amblyopia. In the present multiple regres- of age. Moreover, cryotreated severe ROP was a signifi- sion analysis, the presence of astigmatism at 21⁄2 years cant risk factor for astigmatism at 10 years of age. of age was a risk factor for astigmatism at 10 years, but Of the original preterm cohort, 198 (79.8%) of 248 the presence of astigmatism at 6 months of age had no children underwent refraction at 6 months, 21⁄2 years, and apparent effect on astigmatism subsequently. Children 10 years of age and were included in a study of the course with astigmatism of2Dormore at 21⁄2 years of age ran of refraction. The development of spherical equivalents a 40-times-higher risk of developing astigmatism than in the same population has also been reported.9 Only a those without. However, those with astigmatism of 1 D few population-based studies of the refractive outcome or more but less than 1.5 D also ran a significantly higher at school age have been performed in preterm children risk of developing astigmatism at 10 years of age. who had been screened for ROP,4-7 and even fewer have Although not statistically significant, the prevalence 13 been performed on the development of refraction. Most of astigmatism in cryotreated eyes increased between 21⁄2 of the hospital-based studies discuss the development of and 10 years of age. This was in accordance with the spherical equivalents,14-16 and hardly any have longitu- American Cryotherapy for Retinopathy of Prematurity dinally evaluated the development of astigmatism in pre- Trial.18 Quinn et al18 reported an increase in the preva- term children.17,18 lence of astigmatism during the first 10 years of life in In the present study, the amount and prevalence of astig- cryotreated eyes and untreated eyes with threshold ROP. matism declined during the first 21⁄2 years of life, unlike A higher frequency of astigmatism in cryotreated eyes at the study by Theng et al,17 who found an increase in astig- 10 years of age, compared with untreated eyes, was also matism during the first 3 years of life in preterm children. shown, which would suggest that cryotreatment may affect This difference may be partly owing to a greater dropout the long-term growth of the eye. This finding could not rate in their study. The decrease in astigmatism in our study be evaluated in the present study because all of the chil- accorded with the findings in studies of growing children fulfilling the criteria for treatment had been treated.10 dren.19-21 However, in the present study, the prevalence of The prevalence of against-the-rule astigmatism was astigmatism remained stable from 21⁄2 to 10 years of age, higher at younger ages for preterm children, as is the case

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©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 A B C Total Study Group (N = 197) No ROP (n = 117) Mild ROP (n = 41) 50 50 50 ≥ 2 D ≥ 2 D ≥ 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D 40 40 40

30 30 30

Percentage 20 Percentage 20 Percentage 20

10 10 10 2 7 11 9 1 2 1 2 2 8 6 7 3 3 1 1 0 0 0 6 mo 2½ y 10 y 6 mo 2½ y 10 y 6 mo 2½ y 10 y Age Age Age

D E Untreated Severe ROP (n = 15) Cryotreated Severe ROP (n = 24) 50 50 ≥ 2 D ≥ 2 D ≥ 1 D and < 2 D ≥ 1 D and < 2 D 40 40

7 30 30 7

Percentage 20 Percentage 20 5

10 10 2 2 1 1 2 0 0 0 6 mo 2½ y 10 y 6 mo 2½ y 10 y Age Age

Figure 2. Prevalences of anisometropia of 1 diopter (D) or more in the preterm cohort at 6 months, 2½ years, and 10 years of age. ROP indicates retinopathy of prematurity.

Table 5. Cases of Lost Anisometropia and New Cases Table 6. Results of Stepwise Multiple Regression Analysis of Anisometropia (Ն1D)* of Risk Factors for Anisometropia (Ն1 D) at 10 Years of Age

Age Lost Cases New Cases Total Anisometropia Anisometropia at Age 2½ y OR (95% CI) P Value 6mo 15 2½ y7 9 17 Ն1 and Ͻ2 D 5.80 (0.58-57.62) .13 10 y 7 6 16 Ն2 D 130.50 (23.02-739.70) Ͻ.001

Abbreviation: D, diopter. Abbreviations: CI, confidence interval; D, diopter; OR, odds ratio. *Data are expressed as number of cases.

in a normal population of children, but the prevalence term children at all 3 examinations.7,8 The amount of an- remained high and was more common at 10 years of age isometropia, however, increased slightly, unlike in the than was with-the-rule astigmatism, unlike the findings studies of the normal population.31,33,34 Abrahamsson and in the latter group.22,28 The prevalence of oblique astig- Sjo¨strand35 reported that high anisometropia (Ն3D)at matism was also higher than in a normal population of 1 year of age will probably persist, which was also the children28 and showed no change during the study. These case in the present study, in which children with high findings may be of importance for follow-up examina- anisometropia (Ն2 D) remained anisometropic during tions of preterm children with astigmatism, because the study. This was confirmed by the multiple regres- against-the-rule and oblique astigmatism are risk fac- sion analysis in which anisometropia of2Dormore at 29,30 tors for amblyopia. 21⁄2 years of age was the only significant risk factor for The prevalence of anisometropia (Ն1 D) remained the anisometropia of1Dormore at 10 years of age. same during the study, as in studies of children in the In the preterm cohort, the children with cryotreated normal population,31,32 although it was higher than in full- severe ROP had the highest prevalence of anisometro-

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©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 pia on all 3 retinoscopic examination results, and also the highest prevalence of high anisometropia (Ն2 D). Table 7. Sensitivity and Specificity of Various Thresholds Moreover, no change in prevalence occurred during this of Refraction at 2½ Years of Age as Regards Anisometropia (Ն1 D) at 10 Years of Age period, which suggests that the process of emmetropization had already been disturbed early in life. No. of Many aspects must be taken into account when dis- Threshold of Cases of cussing ophthalmological follow-up examinations of pre- Anisometropia Anisometropia term children. Recently, the American Cryotherapy for at Age 2½ y, D Missed at Retinopathy of Prematurity Trial published a report of (No. of Eyes) Sensitivity, % Specificity, % Age 10 y their 15-year follow-up of eyes with cryotreated and Ն0.5 (44) 81.2 82.9 3 threshold ROP.36 They emphasized the need for regular Ն0.75 (26) 75.0 92.3 4 follow-up examinations of these children because reti- Ն1 (17) 62.5 96.1 6 Ն1.5 (12) 56.2 98.3 7 nal detachment and other ROP-related complications may Ն2 (11) 56.3 98.9 7 occur after 10 years of age. In our cohort, children with cryotreated severe ROP had the highest prevalence of refractive errors during the first 10 years of life, which change at 10 years of age and therefore should be fol- also favors follow-up of such children. However, we lowed up. However, other studies have found a correla- found no difference in the prevalences of refractive er- tion between visual outcome and a lower degree of an- rors at 10 years of age between the eyes without ROP isometropia.37,38 This would suggest that the cutoff of and those with mild or untreated severe ROP,7 and no anisometropia should be at a lower level, such as1Dor difference in the course of refractive development as re- more or 1.5 D. gards astigmatism and anisometropia (present study) or the spherical equivalent.9 Therefore, apart from cryotreated severe ROP, the stage of ROP should not be CONCLUSIONS used as a criterion for follow-up examinations of refractive errors in our population. Preterm children, regardless of the stage of ROP, run a In the present cohort, a previous refractive error was higher risk of developing refractive errors than those born a risk factor for subsequent ones. However, retino- at term. In this population-based study, we found that a scopic examination findings at 6 months of age did not refractive error at 21⁄2 years of age predicts that refrac- predict refractive errors at 10 years of age. The findings tive error will also be present at 10 years of age. Al- in the American Cryotherapy for Retinopathy of Prema- though the children who underwent cryotherapy had the turity Trial indicated that no change occurred in myo- highest prevalence of refractive errors, the course of re- pia after 1 year of age in preterm children without ROP fractive development was similar in all subgroups of pre- or with nonthreshold ROP.15 In the present cohort, the term children. Recommendations for follow-up exami- children were not examined at 1 year of age, but retino- nations must include all aspects of visual function, ie, scopic findings at 21⁄2 years of age significantly pre- visual acuity, contrast sensitivity, and visual fields, as well dicted future myopia,9 as well as astigmatism and aniso- as the refraction, strabismus, and perceptual problems. metropia (present study). At 21⁄2 years of age, it is still All preterm children should be included in such fol- possible to prevent amblyopia and prescribe eyeglasses low-up examinations for refractive error, irrespective of to improve the development of vision. Therefore, we rec- the ROP stage. ommend that all preterm children have follow-up examinations at about this age. Submitted for Publication: March 2, 2006; final revi- Recommendations for thresholds of refractive errors sion received May 10, 2006; accepted May 14, 2006. for follow-up examinations are necessarily based on the Correspondence: Eva K. Larsson, MD, PhD, Depart- economic resources of the local community. The sensi- ment of Ophthalmology, Uppsala University Hospital, 751 tivity and specificity of various cutoff thresholds for spheri- 85 Uppsala, Sweden ([email protected]). cal equivalents at 21⁄2 years of age have been reported else- Financial Disclosure: None reported. where (ie, Holmstro¨m and Larsson [2005]9). Thresholds Funding/Support: This study was supported by Stif- of less than 0.5 D or of less than 0 D spherical equiva- telsen Synfra¨mjandets Foundation for Research and the lents were suggested for such follow-up examinations. Crown Princess Margaretha Foundation for Visually Im- In the present study of astigmatism and anisometropia, paired. we found it more difficult to find a threshold with both Acknowledgment: We thank Elisabeth Berg, Depart- high sensitivity and high specificity (Tables 4 and 7). A ment of Humanities, Informatics and Social Sciences, Ka- cutoff at 0.75 D or more or1Dormore for astigmatism rolinska Institutet, for her valuable advice about the sta- would have the highest sensitivity and specificity, but 10 tistical analyses, and the Swedish National Board of Health and 14, respectively, of the 41 children with astigma- and Social Welfare, for their help. tism at 10 years of age would still have been missed. The levels of sensitivity for anisometropia were poor, prob- REFERENCES ably because of the large number of cases who lost their anisometropia and new cases of anisometropia (Table 5) 1. Robinson R, O’Keefe M. Follow-up study on premature infants with and without during the study. Nine (82%) of the 11 children with high retinopathy of prematurity. Br J Ophthalmol. 1993;77:91-94. anisometropia (Ն2D)at21⁄2 years of age showed no 2. Schalij-Delfos NE, de Graaf ME, Treffers WF, Engel J, Cats BP. Long term follow

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