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Glasses Versus Observation for Moderate Bilateral Astigmatism in 1- to <7-Year-Olds

Published:August 02, 2021DOI:https://doi.org/10.1016/j.ajo.2021.07.029

      Purpose

      To compare visual outcomes in children with moderate bilateral astigmatism treated with glasses with those who were merely observed.

      Design

      Retrospective case series.

      Methods

      The medical records of all children 1 to <7 years of age who were diagnosed with moderate bilateral astigmatism (+1.25 to +3.25 diopters [D]) at a single institution over a 12-year period were retrospectively reviewed. Children with anisometropia ≥1.00 D, hyperopia ≥+3.00 D, myopia ≥−3.00D, amblyopia, or strabismus at diagnosis were excluded. Observation or full spectacle correction of astigmatism was at the provider's discretion. Kaplan–Meier rates of developing amblyopia and strabismus were assessed over a minimum follow-up of 18 months.

      Results

      Eighty-five (6.9%) of 1235 subjects met the inclusion criteria; 58 (68.2%) were prescribed glasses while 27 (31.8%) were observed. The groups differed by mean age at diagnosis (3.56 ± 1.42 years for observed vs 4.31 ± 1.36 years for glasses [P = .03]) and mean amount of astigmatism (1.73 ± 0.43 D for observed vs 2.00 ± 0.51 D for glasses [P = .02]). By 4 years of follow-up, the Kaplan–Meier rate of developing amblyopia was 8.3% (95% confidence interval [CI] 0%-19.4%) in the observed group and 10.3% (95% CI 1.5%-19.1%) in the glasses group [P = .74] while strabismus was 7.1% (95% CI 0%-20.6%) among those observed and 7.1% (95% CI 0.4%-13.8%) of those prescribed glasses [P = .60].

      Conclusions

      Rates of amblyopia and strabismus were similar and modest in this cohort of children with moderate bilateral astigmatism treated with glasses vs observation. These results suggest that prescribing glasses for these children may be no better than observation in preventing the development of amblyopia or strabismus.
      Uncorrected astigmatism in infants and young children is associated with the development of amblyopia.
      • Mitchell DE
      • Freeman RD
      • Millodot M
      • Haegerstrom G.
      Meridional amblyopia: evidence for modification of the human visual system by early visual experience.
      • Dobson V
      • Miller JM
      • Harvey EM
      • Mohan KM.
      Amblyopia in astigmatic preschool children.
      • Harvey EM
      • Dobson V
      • Miller JM
      • Clifford-Donaldson CE.
      Amblyopia in astigmatic children: patterns of deficits.
      While there is little doubt that children presenting with astigmatism and amblyopia should be managed with astigmatic spectacle correction, there is scant empirical evidence as to whether astigmatic children without amblyopia at diagnosis would benefit from optical correction. The current guidelines for prescribing glasses for astigmatism in children are based on surveys of eye care providers and not on visual outcomes.
      • Miller JM
      • Harvey EM.
      Spectacle prescribing recommendations of AAPOS members.
      • Harvey EM
      • Miller JM
      • Dobson V
      • Clifford CE.
      Prescribing eyeglass correction for astigmatism in infancy and early childhood: a survey of AAPOS members.
      • Farbrother JE.
      Spectacle prescribing in childhood: a survey of hospital optometrists.
      AAO PPP Pediatric Ophthalmology/Strabismus Panel, Hoskins Center for Quality Eye Care. Pediatric eye evaluations PPP - 2017.
      The purpose of this study is to compare visual outcomes in children with moderate bilateral astigmatism (range +1.25 to +3.25 diopters [D]) and normal vision at diagnosis who were treated with glasses with those who were merely observed. A better understanding of the risk for developing amblyopia in this group of children will help providers minimize astigmatic amblyopia while avoiding the burden of spectacle overtreatment.

      METHODS

      The medical records of all patients 1 to <7 years of age who were diagnosed with regular astigmatism at the Mayo Clinic from January 1, 2005, through December 31, 2016, were retrospectively reviewed. Institutional review board approval was obtained for this study. All children underwent a complete ophthalmic examination including a cycloplegic refraction performed 30 minutes after receiving 1% or 2% cyclopentolate; those having moderate bilateral astigmatism (+1.25 to +3.25 D) without concurrent astigmatic anisometropia (≥+1.00) were included in the study. Astigmatic anisometropia was defined as a difference of ≥+1.00 of cylinder between corresponding meridians between the 2 eyes. Excluded patients included those with, at the initial examination, concurrent hyperopia (≥+3.00 D), hyperopic anisometropia (≥+1.00 D), myopia (≥−3.00 D), myopic anisometropia (≥+1.00 D), amblyopia (defined as a difference of ≥2 lines in visual acuity between the eyes with HOTV letters, Allen figures, Snellen, or Early Treatment Diabetic Retinopathy Study charts, or a difference between fixation preference in preverbal children), strabismus of any type (measured by the prism and alternate cover test), or structural ocular pathology. Both hyperopic and myopic anisometropia were defined as a difference of ≥+1.00 between the spheres. Subjects with significant developmental delay were also excluded given the difficulty of discerning an accurate visual acuity.
      Patients ≥3 years of age were required to have age-normal distance visual acuity
      • Drover JR
      • Felius J
      • Cheng CS
      • Morale SE
      • Wyatt L
      • Birch E.
      Normative pediatric visual acuity using single surrounded HOTV optotypes on the Electronic Visual Acuity Tester following the Amblyopia Treatment Study protocol.
      in each eye (20/50 or better for age 36-47 months [3 years], 20/40 or better for age 48-59 months [4 years], and 20/32 or better for ≥5 years of age) with HOTV letters, Allen figures, Snellen, or Early Treatment Diabetic Retinopathy Study testing. Children <3 years of age who were unable to perform subjective visual acuity testing were required to have central, steady, maintained, or fix and follow visual acuity in both eyes without evidence of fixation preference per the examiner's documentation.
      The determination to prescribe spectacle correction was at the discretion of the examiner and not based on a specific protocol. In general, one clinician tended not to prescribe glasses for moderate bilateral astigmatism in young children while a second prescribed spectacles routinely. Those obtaining glasses generally received a prescription correcting their full cycloplegic refraction. Only those patients with ≥18 months of follow-up to a minimum age of 4 years and to a maximum of <10 years at the final examination were included in the study. The primary outcome measures were the development of amblyopia and strabismus within the follow-up period. The diagnosis of amblyopia and/or strabismus was made by the clinician who observed the patient within the follow-up period, as documented in the medical record.
      Comparisons between the treated and the observed group were assessed by a χ2 test for independence for categorical variables. The Wilcoxon rank-sum test was used to compare continuous variables between the 2 groups. Follow-up outcomes were estimated using the Kaplan–Meier method
      • Kaplan EL
      • Meier P.
      Nonparametric estimation from incomplete observations.
      while the log-rank test was used to compare the projections between the groups. The threshold of significance was set at α = 0.05.

      RESULTS

      Eighty-five (6.9%) of 1235 individually reviewed distinct patient charts met the inclusion criteria, of which 58 (68.3%) were managed with glasses and 27 (31.8%) were simply observed for the duration of the follow-up period. The baseline historical and clinical characteristics of the 85 subjects are shown in Table 1. The groups differed by median age at diagnosis (3.41 years for observed vs 4.31 years for glasses [P = .03]) and median amount of astigmatism at diagnosis (1.75 D for observed vs 1.94 D for glasses [P = .02]). The mean follow-up for the 85 subjects was 3.7 (±1.5 SD) years, with 3.6 ± 1.6 years for the observed group and 3.8 ± 1.2 years for the glasses group. The Kaplan–Meier rate of developing amblyopia by 4 years of follow-up was 8.3% (95% CI 0%-19.4%) in the observed group and 10.3% (95% CI 1.5%-19.1%) in the glasses group [P = .74]; Figure 1). The Kaplan–Meier rate of developing strabismus was 7.1% (95% CI 0%-20.6%) among those observed and 7.1% (95% CI 0.4%-13.8%) of those prescribed glasses (P = .60; Figure 2).
      TABLE 1Baseline Characteristics of 85 Patients With Bilateral Moderate Astigmatism, 27 Observed and 58 Treated With Glasses.
      CharacteristicObservation (n = 27)Glasses (n = 58)P Value
      Male sex, n (%)14 (52)28 (48).75
      Mean ± SD age at diagnosis (y) (median)3.56 ± 1.42 (3.41)4.31 ± 1.36 (4.31).03
      White race, n (%)16 (59)37 (63).80
      Hispanic/Latino ethnicity, n (%)5 (19)9 (16).75
      History of prematurity, n (%)3 (11)4 (7).51
      Mean ± SD cylinder
      Mean amount of cylinder between the 2 eyes, measured by cycloplegic refraction.
      at diagnosis (median)
      1.73 ± 0.43 (1.75)2.00 ± 0.51 (1.94).02
      a Mean amount of cylinder between the 2 eyes, measured by cycloplegic refraction.
      FIGURE 1
      FIGURE 1Kaplan–Meier estimates of amblyopia in the glasses and observation arms over 4 years from initial visit.
      FIGURE 2
      FIGURE 2Kaplan–Meier estimates of strabismus in the glasses and observation arms over 4 years from initial visit.
      The Kaplan–Meier rates of developing amblyopia between a lower cylinder (+1.25 D to <+2.00 D) group and a higher (+2.00 to +3.25 D) group, and between a younger age (1-<4 years) at diagnosis to an older age (4-<7 years) were compared (Table 2). Higher rates of amblyopia occurred among the children with higher cylinder values compared with those with lower values in both the glasses (13.8% vs 6.9%) and observation (11.1% vs 5.5%) groups. However, the use of glasses did not provide a significant difference in amblyopia prevention for either the lower (P = .95) or higher cylinder group (P = .73). Glasses similarly provided no significant difference in the development in amblyopia for children diagnosed at a younger age (P = .62) or at an older age (P = .95).
      TABLE 2Subgroup Analysis for Development of Amblyopia by 4 Years Follow-up, Separated by Higher and Lower Cylinder and Younger and Older Age.
      ObservationGlassesP Value
      NAmblyopia, n (%)NAmblyopia, n (%)
      Cylinder
      Mean amount of cylinder between the 2 eyes, measured by cycloplegic refraction.
      at diagnosis (diopters)
      +1.25 to <+2.00181 (5.5%)292 (6.9%).95
      +2.00 to +3.2591 (11.1%)294 (13.8%).73
      Age at diagnosis (y)
      1-<4161 (6.3%)213 (14.2%).62
      4-<7111 (9.1%)373 (8.1%).95
      a Mean amount of cylinder between the 2 eyes, measured by cycloplegic refraction.

      DISCUSSION

      In this study of children 1 to <7 years of age with moderate bilateral astigmatism and normal visual acuity treated with either spectacle correction or observation, the rate of developing amblyopia or strabismus after ≥18 months was similar and modest in both groups. Moreover, in a subgroup analysis concerning the development of amblyopia alone, there was no benefit of wearing glasses for children with higher amounts of astigmatism or who were younger at the time of diagnosis.
      There are few reports with which to compare the findings of this study. A series of studies of preschool and school-aged children of the Tohono O'odham Nation, a Native American tribe in Arizona with a high prevalence of high bilateral with-the-rule astigmatism, demonstrated an improvement in vision among those wearing glasses for 2 years
      • Dobson V
      • Clifford-Donaldson CE
      • Green TK
      • Miller JM
      • Harvey EM.
      Optical treatment reduces amblyopia in astigmatic children who receive spectacles before kindergarten.
      but not for durations as short as 4 months.
      • Harvey EM
      • Dobson V
      • Miller JM
      • Sherrill DL.
      Treatment of astigmatism-related amblyopia in 3- to 5-year-old children.
      However, these studies likely included patients with amblyopia at diagnosis and are therefore unable to unequivocally determine whether children with bilateral astigmatism and normal vision benefit from spectacle correction. There are no other known studies evaluating the risk of amblyopia and strabismus among children presenting with normal vision and moderate bilateral astigmatism.
      Previous reports suggest that uncorrected astigmatism in early childhood can lead to reduced visual acuity in the orientation of the axis of astigmatism that persists despite optical correction beyond the critical period of visual development (meridional amblyopia).
      • Mitchell DE
      • Freeman RD
      • Millodot M
      • Haegerstrom G.
      Meridional amblyopia: evidence for modification of the human visual system by early visual experience.
      • Dobson V
      • Miller JM
      • Harvey EM
      • Mohan KM.
      Amblyopia in astigmatic preschool children.
      • Harvey EM
      • Dobson V
      • Miller JM
      • Clifford-Donaldson CE.
      Amblyopia in astigmatic children: patterns of deficits.
      Susceptibility to the effects of astigmatic blur appears to begin between 1 and 3 years of age,
      • Dobson V
      • Miller JM
      • Harvey EM
      • Mohan KM.
      Amblyopia in astigmatic preschool children.
      ,
      • Gwiazda J
      • Bauer J
      • Thorn F
      • Held R.
      Meridional amblyopia does result from astigmatism in early childhood.
      although the amount of astigmatism that poses a significant risk at different ages is unknown. Evidence suggests that meridional amblyopia may be reduced or eliminated by the optical correction of astigmatism before 7 years of age.
      • Mitchell DE
      • Freeman RD
      • Millodot M
      • Haegerstrom G.
      Meridional amblyopia: evidence for modification of the human visual system by early visual experience.
      ,
      • Dobson V
      • Miller JM
      • Harvey EM
      • Mohan KM.
      Amblyopia in astigmatic preschool children.
      ,
      • Dobson V
      • Clifford-Donaldson CE
      • Green TK
      • Miller JM
      • Harvey EM.
      Optical treatment reduces amblyopia in astigmatic children who receive spectacles before kindergarten.
      ,
      • Gwiazda J
      • Bauer J
      • Thorn F
      • Held R.
      Meridional amblyopia does result from astigmatism in early childhood.
      ,
      • Cobb SR
      • MacDonald CF.
      Resolution acuity in astigmats: evidence for a critical period in the human visual system.
      While astigmatism of ≥1.50 D has been reported to occur in ≤9% of preschool- and school-aged children
      • McKean-Cowdin R
      • Varma R
      • Cotter SA
      • et al.
      Risk factors for astigmatism in preschool children: the multi-ethnic pediatric eye disease and Baltimore pediatric eye disease studies.
      and is the most frequent cause of automated vision screening failure and referral,
      • Margines JB
      • Huang C
      • Young A
      • et al.
      Refractive errors and amblyopia among children screened by the UCLA Preschool Vision Program in Los Angeles County.
      ,
      • Vaughan J
      • Dale T
      • Herrera D
      • Karr D.
      Oregon Elks Children's Eye Clinic vision screening results for astigmatism.
      there are no known previous reports comparing observation to spectacle correction in children with moderate bilateral astigmatism and age-normal visual acuity at diagnosis.
      There are several limitations to the findings of this study. Its retrospective design precludes standardized testing, equitable randomization, and structured follow-up. It was not possible to ensure compliance with the use of glasses; if some children who were prescribed glasses did not wear them consistently, it would have been less likely to find a difference between groups when one was present. The study also suffers from small sample sizes, due primarily to the rigorous inclusion criteria, particularly for subgroups. The results may also be biased by the differences in baseline characteristics between the treatment and observation groups. Specifically, the treatment group was older and had higher amounts of astigmatism at diagnosis. If the older children had not yet developed amblyopia at diagnosis, it may have been less likely to ever develop. We further acknowledge the large age range of the participants in the study, and that there may be substantial differences in the visual development trajectories of a 1-year-old and a 6-year-old. However, amblyopia was not more prevalent among the younger children in the observation group. Finally, children presenting without amblyopia at diagnosis may be less likely to develop it without optical correction, and thereby the study may be self-selecting for children who are at low risk of developing amblyopia. The goal of the study, however, was to study children with moderate bilateral astigmatism presenting with normal vision.
      The prevention of amblyopia or strabismus is not the sole indication for prescribing spectacles for young children with moderate bilateral astigmatism. Other benefits to using glasses include improved visual function and decreased asthenopia, and any decision for prescribing glasses should be made on an individual basis. However, because photoscreening has become increasingly commonplace in many primary care settings, an expanding number of asymptomatic children are being referred to eye specialists for astigmatic refractive error. The inference from the conclusions of this study is that some of these children who are asymptomatic may be at risk of overtreatment.
      The findings of this study suggest that glasses may be no better than observation in preventing the development of amblyopia in children with moderate bilateral astigmatism. A larger, prospective, randomized trial is warranted to confirm these results and provide further stratification by age and amount of astigmatism.
      All authors have completed and submitted the ICMJE form for disclosure of potential conflicts of interest.
      Funding/Support: Supported by the Department of Ophthalmology Development Fund at the Mayo Foundation. Financial Disclosures: The authors indicate no financial support or conflicts of interest. All authors attest that they meet the current ICMJE criteria for authorship.

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