Abstract
Purpose
To describe the prevalence of structural disorders of the eye and nystagmus in preschool-aged children.
Methods
Population-based evaluation of children 6 months through 71 months of age in Baltimore, Maryland, United States.
Results
Among 4,132 children identified from 54 census tracts, 3,990 eligible children (97%) were enrolled and 2,546 children (62%) were examined. Structural disorders were found in 41 children and nystagmus in 9 children for an overall prevalence of 1.96% (95% CI, 1.46%–2.59%). Only 11 (0.43%; 95% CI, 0.22%–0.77%) had vision loss in at least one eye, most often due to posterior segment disease.
Conclusions
Structural ocular abnormalities and nystagmus combined are present in nearly two percent of preschool-aged children in this population-based study. Vision loss due to these abnormalities is uncommon.
The Baltimore Pediatric Eye Disease Survey (BPEDS) was conducted to determine the prevalence of decreased visual acuity, strabismus, amblyopia, refractive error, and “other ocular disorders”—defined in this study as nystagmus or structural abnormalities of the ocular adnexa, the anterior segment, or the posterior segment—in a population-based sample of African American and non-Hispanic white children 6 months through 71 months of age living in Baltimore, Maryland. Prevalence information concerning the population-based disease burden associated with specific eye and vision problems can aid policy makers developing screening and treatment programs for eye problems. The purpose of this study was to describe the prevalence of other ocular disorders in the BPEDS cohort.
Methods
The protocol was approved by the institutional review board (IRB) of the Johns Hopkins Bloomberg School of Public Health as well as the Battelle Centers for Public Health Research and Evaluation IRB and the IRB of the Maryland Department of Health and Mental Hygiene. Parents or legal guardians provided written, informed consent for their child’s participation. A detailed description of the BPEDS protocol has been published.1
The study enrolled subjects from 54 contiguous census tracts in northeastern and eastern Baltimore City and adjacent portions of eastern Baltimore County. Parents or guardians of all enrolled subjects were invited to bring their child to the study clinic for a detailed interview and ophthalmological examination, including optotype visual acuity testing using the Amblyopia Treatment Study (ATS) visual acuity protocol for children 30 to 71 months of age (if possible)2; fixation preference testing at near; testing of ocular alignment at distance and near fixation; and examinations of the ocular adnexa, anterior segment, and posterior segment with pupillary dilation. Data were entered in real time into an electronic study record. Decreased visual acuity was defined as worse than 20/50 for children <4 years of age and worse than 20/40 for those ≥4 years among those subjects who were testable with appropriate refractive correction.1 Two children could not complete optotype testing; in these, reduced vision was diagnosed following the study team’s review of the records for clinical findings that would likely cause visual loss (one subject had optic nerve hypoplasia and the other had nystagmus).
Records coded with strabismus, decreased vision, nystagmus, and structural disorders were retrieved and reviewed for visual outcomes. These data vary slightly from prior BPEDS reports because we have included the entire study population sample here rather than just the two races reported in the primary study reports.1,3,4 Data for refractive error, amblyopia, and vision loss have been previously reported.1,3,4 Prevalence of other disorders was calculated as the number affected divided by the number examined. For these estimates, 95% confidence intervals were calculated using exact Poisson estimates around the mean event rate.
Results
We identified 63,737 occupied dwelling units in 54 census tracts. Among 4,132 children identified as eligible, 3,990 (97%) were enrolled and 2,546 (62%) were examined (1,309 boys). Study participants included 1,030 white children, 1,268 African Americans, 218 “others” and 30 with missing racial/ethnic information.
A total of 159 children (6.2% [95% CI, 5.3%–7.3%]: 68 white, 73 African American, 18 other) had abnormalities of alignment, vision, nystagmus, or structural abnormalities; of these, 71 (45%) were girls. Children not examined were similar to those examined in terms of race or ethnicity, gender, parent-rated eye health of the child, the proportion of parents reporting that the child had difficulty seeing in the past year, the proportion of parents reporting that the child had a prior diagnosis of an eye problem, and parent-rated general health of the child. Younger children were less likely to be examined, while those with health problems, those with stay-at-home mothers and those with parents with relatively more education were more likely to be examined.
Other ocular disorders were identified in 50 children (1.96% [95% CI, 1.46%–2.59%]: 23 white, 24 African American, 3 Hispanic). Prematurity was reported for 19 (38%), with 2 additional children of uncertain gestational age. Structural ocular disorders were found in 41 children, 8 of whom had vision loss; nystagmus was found in 9 children, 3 of whom had vision loss (Table 1).
Table 1.
Structural abnormalities and nystagmus recorded in the Baltimore Pediatric Eye Disease Survey
| Cohort (N = 2,546) | With vision loss | |
|---|---|---|
| Number (%) | Number (%) | |
| Eyelids | 9 (0.35) | 1 (0.04) |
| Nasolacrimal duct obstruction | 2 (0.08) | 0 |
| Anterior segmenta | ||
| Cornea | 2 (0.08) | 0 |
| Irisb | 6 (0.24) | 0 |
| Lens | 2 (0.08) | 1 (0.04) |
| Conjunctivitis | 4 (0.16) | 0 |
| Posterior segment | ||
| Retina | 10 (0.39) | 4 (0.16) |
| Optic nervec | 6 (0.24) | 2 (0.08) |
| Nystagmus | 9 (0.35) | 3 (0.12) |
| Total ocular abnormalities excluding refractive error, decreased vision, and strabismus | 50 (1.96) | 11 (0.43) |
One subject had an abnormality of the lens and iris, categorized as lens.
Including coloboma (1), heterochromia (2), corectopia (1), iris stromal atrophy (1), and postsurgical changes (1).
Optic nerve cupping/atrophy (4), optic nerve pit (1), optic nerve hypoplasia (1).
Disorders of the posterior segment were observed in 16 subjects and disorders of the anterior segment in14. Posterior segment disorders were often associated with vision loss (6 of 16 subjects), whereas disorders of the anterior segment (including most frequently iris anomalies and conjunctivitis) rarely caused vision loss (1 of 14 subjects).
By comparison, strabismus was found in 67 of 2,546 subjects (2.6%) of this BPEDS cohort, equally distributed between esotropia and exotropia. One case of Duane syndrome and 2 of dissociated vertical deviation were identified. Decreased vision after attempted refractive correction in at least one eye from any cause was found in 24 of 1,470 subjects (1.6%) subjects 36 months or older in BPEDS, about one-third each due to amblyopia, not amblyopia, and unclassified.
Discussion
In this population-based study, we identified at least one eye abnormality in 6.2% of our cohort of preschool children aged 6–71 months in Baltimore, Maryland. Most of these disorders were either decreased vision or strabismus. Other ocular disorders were encountered at a low rate in this population of children, with a prevalence of 1.96%. The majority of these disorders were incidental, as the prevalence of abnormalities significant enough to be associated with vision loss was very uncommon, found in only 0.43% of the cohort.
There are few population-based reports of preschool-aged children regarding this set of disorders with which we can compare our rate of visual impairment from ocular pathologies. Visual impairment was noted in 2 of 1,118 patients (0.2%) from ocular pathology in the Sydney Eye Study.5 The Multi-Ethnic Pediatric Eye Disease Study (MEPEDS) Group from Los Angeles, California, found 6 of 3,835 patients (0.2%) with vision impairment from ocular diseases.6
The cross-sectional Millennium Cohort Study, based solely on parental interviews at age 3 years, reported a prevalence of 5.7% for any eye condition and a prevalence of 0.24% visual loss.7 The prevalence of all conditions is similar to that in BPEDS, while the visual impairment rate is slightly lower. It is likely that because visual acuity was not tested in the Millenium Cohort Study some cases of vision loss may have been missed.
Recruiting subjects for BPEDS was challenging, and we examined only 62% of eligible children; nevertheless, data from the enrollment interview of parents and guardians completed for 97% of eligibile children indicate that those who were examined were similar in terms of race/ethnicity, sex, quality of eyesight, and occurrence of visual problems in the prior year compared with children who were not examined. It is thus unlikely that the current estimates are subject to major nonresponse bias. Moreover, we did not include visual acuity data based on fixation preference testing for children unable to perform ATS single-surrounded HOTV optoypes because we have found it to be unreliable.8,9 This means that we may have underestimated the proportion of children with visual loss, since we did not have use of quantitative measures among the entire cohort. This could be particulary true for young children with nystagmus.
In conclusion, other ocular disorders were unusual in a predominantly African American and non-Hispanic white cohort of preschool-aged children. More than 80% of these disorders were not visually significant. Development of screening methods targeting these problems would not seem warranted as the large majority would be detected by current screening strategies based on determination of visual acuity and strabismus. Refractive error screening might miss some of the posterior segment abnormalities, but treatment options for these conditions are largely absent, reducing any adverse outcome from this strategy.
Acknowledgments
Financial support: Supported by the National Eye Institute, National Institutes of Health, Bethesda, MD (EY14483).
Footnotes
Conflicts of interest: The authors have no proprietary or commercial interest in any materials discussed in the manuscript.
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