Normative visual acuity in infants and preschool-aged children in Sydney.

PURPOSE: To provide population-based normative visual acuity (VA) by age, in children participating in the Sydney Paediatric Eye Disease Study aged 6 to <72 months. METHODS: Monocular VA was measured using the Amblyopia Treatment Study (ATS HOTV) protocol (24 to <72 months). Some children were also tested using linear ETDRS or HOTV logMAR VA charts (30 to <72 months). If unable to perform recognition acuity, the Teller Acuity Cards II (TAC II) was performed (6 to <42 months). Children with significant refractive error or ocular disease were excluded. RESULTS: Improvement in VA with age was shown on all three vision tests (all p < 0.0001). Mean VA using ATS HOTV (n = 836) was 0.13 logMAR (6/8) at <36 months, which improved to -0.01 (6/6) at 66 to <72 months. Mean ETDRS/HOTV (n = 399) VA was 0.26 logMAR (6/11) at <36 months, which improved to 0.1 (6/7.5) at 66 to <72 months. Mean monocular TAC II (n = 442) was 5.7 cycles/degree (0.72 logMAR) at 6 to <9 months and improved to 12.4 cycles/degree (0.38 logMAR) at age 30 to <33 months. Associations with ATS HOTV VA included prematurity (p = 0.027) and socio economic status (SES) factors such as home ownership (p = 0.039) and employment of one (p = 0.019) or both parents (p = 0.003). CONCLUSIONS: VA norms in children improved with age and were different according to the VA test used. Low SES was associated with poorer VA, supporting the need for test specific VA norms to be established for different populations. The ATS HOTV appears to be the best test to use for vision screening due to its lower false positive referral rate.

Prevalence of anisometropia and its association with refractive error and amblyopia in preschool children.

AIM: To determine the age and ethnicity-specific prevalence of anisometropia in Australian preschool-aged children and to assess in this population-based study the risk of anisometropia with increasing ametropia levels and risk of amblyopia with increasing anisometropia. METHODS: A total 2090 children (aged 6-72 months) completed detailed eye examinations in the Sydney Paediatric Eye Disease Study, including cycloplegic refraction, and were included. Refraction was measured using a Canon RK-F1 autorefractor, streak retinoscopy and/or the Retinomax K-Plus 2 autorefractor. Anisometropia was defined by the spherical equivalent (SE) difference, and plus cylinder difference for any cylindrical axis between eyes. RESULTS: The overall prevalence of SE and cylindrical anisometropia ≥1.0 D were 2.7% and 3.0%, for the overall sample and in children of European-Caucasian ethnicity, 3.2%, 1.9%; East-Asian 1.7%, 5.2%; South-Asian 2.5%, 3.6%; Middle-Eastern ethnicities 2.2%, 3.3%, respectively. Anisometropia prevalence was lower or similar to that in the Baltimore Pediatric Eye Disease Study, Multi-Ethnic Pediatric Eye Disease Study and the Strabismus, Amblyopia and Refractive error in Singapore study. Risk (OR) of anisometropic amblyopia with ≥1.0 D of SE and cylindrical anisometropia was 12.4 (CI 4.0 to 38.4) and 6.5 (CI 2.3 to 18.7), respectively. We found an increasing risk of anisometropia with higher myopia ≥-1.0 D, OR 61.6 (CI 21.3 to 308), hyperopia > +2.0 D, OR 13.6 (CI 2.9 to 63.6) and astigmatism ≥1.5 D, OR 30.0 (CI 14.5 to 58.1). CONCLUSIONS: In this preschool-age population-based sample, anisometropia was uncommon with inter-ethnic differences in cylindrical anisometropia prevalence. We also quantified the rising risk of amblyopia with increasing SE and cylindrical anisometropia, and present the specific levels of refractive error and associated increasing risk of anisometropia.

Diagnostic reliability and normative values of stereoacuity tests in preschool-aged children.

AIM: To establish the range of normal stereoacuity thresholds and evaluate the diagnostic reliability of stereoacuity tests in preschool-aged children. METHODS: 1606 children, aged 24-72 months, had detailed eye examinations and stereoacuity testing. Lang-Stereotest II (LangII) was attempted on all children, Stereo Smile Stereoacuity II Test (SSST) was conducted on children aged < 30 months and on older children who could not complete the Randot Preschool Stereoacuity Test (RPST). The RPST was conducted on children aged ≥ 30 months and on some younger children who passed both the LangII and SSST. RESULTS: Modes for the age groups 24-47 months and 48-72 months were: 200 arcsec for both age groups with the LangII test; 120 arcsec and 60 arcsec, respectively, with the SSST; 100 arcsec and 60 arcsec, respectively, with the RPST. Age-adjusted areas under the curve for detecting amblyopia, strabismus and anisometropia were: for the LangII test, 0.72, 0.68 and 0.60, respectively; for the SSST, 0.73, 0.80 and 0.57, respectively; for the RPST, 0.92, 0.82 and 0.73, respectively. CONCLUSIONS: Normative data for the LangII, RPST and SSST stereoacuity tests were determined for children aged 24-72 months. Sensitivity and specificity at individual disparity levels for detecting anisometropia, amblyopia and strabismus were also determined for RPST and SSST. Using area under age-adjusted receiver operating curves, the RPST was found to be the most reliable in detecting ocular conditions compared with the LangII and SSST tests.

Amblyopia prevalence and risk factors in Australian preschool children.

PURPOSE: To determine the prevalence of and factors associated with amblyopia in a sample of Australian preschool children. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: The Sydney Paediatric Eye Disease Study examined 2461 (73.8% participation) children aged between 6 and 72 months from 2007 to 2009. METHODS: Visual acuity (VA) was assessed in children aged ≥ 30 months using the Electronic Visual Acuity system, and a subset using the logarithm of the minimum angle of resolution chart. Amblyopia was categorized into unilateral and bilateral subtypes: Unilateral amblyopia was defined as a 2-line difference in reduced VA between the 2 eyes, in addition to strabismus, anisometropia, and/or visual axis obstruction; bilateral amblyopia was defined as bilateral reduced VA with either bilateral visual axis obstruction or significant bilateral ametropia. Information on ethnicity, birth parameters, and measures of socioeconomic status were collected in questionnaires completed by parents. MAIN OUTCOME MEASURES: Amblyopia. RESULTS: We included 1422 children aged 30 to 72 months, of whom 27 (1.9%) were found to have amblyopia or suspected amblyopia. Mean spherical equivalent for the amblyopic eyes was +3.57 diopters, with a mean VA of 20/50. Only 3 of the 27 amblyopic children had previous diagnoses or treatments for amblyopia. In regression analysis controlling for age, gender, and ethnicity, amblyopia was significantly associated with hyperopia (odds ratio [OR], 15.3; 95% confidence interval [CI], 6.5-36.4), astigmatism (OR, 5.7; 95% CI, 2.5-12.7), anisometropia (OR, 27.8; 95% CI, 11.2-69.3), and strabismus (OR, 13.1; 95% CI, 4.3-40.4). There were no significant associations of amblyopia with low birthweight (<2500 g), preterm birth (<37 weeks), maternal smoking, age, gender, ethnicity, or measures of socioeconomic status (all P>0.05). CONCLUSIONS: Amblyopia was found in 1.9% of this Australian preschool sample, which is comparable with prevalence rates reported by other recent studies in preschool children. Refractive errors, particularly significant hyperopia and astigmatism, in addition to anisometropia and strabismus, were the major amblyogenic factors. There was a low amblyopia detection rate in this preschool population, which suggests that different strategies are required to improve current vision screening strategies in preschoolers. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Use of visual acuity to screen for significant refractive errors in adolescents: is it reliable?

OBJECTIVE: To detect significant refractive error in a population-based random cluster sample of 12-year-old schoolchildren by using sensitivity and specificity of uncorrected visual acuity (VA). METHODS: The Sydney Myopia Study randomly selected 21 secondary schools stratified by socioeconomic status. All year 7 students (mean age, 12.7 years) were invited to participate. We tested VA monocularly, unaided at 2.44 m, using a retroilluminated logMAR chart. Cycloplegic autorefraction (induced with instillation of cyclopentolate hydrochloride, 1%) was used to define clinically significant refractive error as a spherical equivalent of -1.00 diopters (D) or less for myopia; at least +2.00 D for hyperopia; and -1.00 D or less cylinder power for astigmatism. RESULTS: Data for both eyes were pooled for a total of 4497 observations. The sensitivity and specificity for all clinically significant refractive errors at the best VA cutoff level of 53 letters (6/6(-2)) were 72.2% and 93.3%, respectively. Myopia had the highest sensitivity and specificity of any of the refractive errors for detection using VA (97.8% and 97.1%, respectively, for a 45-letter VA cutoff [6/9.5]). The best VA cutoffs for hyperopia and astigmatism were 57 (6/6(+2)) and 55 (6/6) letters, respectively, with sensitivities of 69.2% and 77.4%, respectively, and specificities of 58.1% and 75.4%, respectively. CONCLUSIONS: In this adolescent group, a VA cutoff of 6/9.5 or less detects myopic refractive error reliably. However, there is no reliable VA cutoff for clinically significant hyperopia or astigmatism. Improved VA screening methods are required to improve detection of these conditions. Even so, with the methods described herein, the prevalence of uncorrected VA may provide a reasonably accurate estimate of the prevalence of myopia.

Prevalence of heterophoria and associations with refractive error, heterotropia and ethnicity in Australian school children.

AIMS To establish the prevalence of heterophoria and its association with refractive error and ethnicity in a population-based study of Australian schoolchildren. METHODS The Sydney Myopia Study is a stratified, random cluster (school-based) sample of 4093 students (examined: 2003-2005). Two samples aged 6 (n=1692) and 12 years (n=2289) without heterotropia were included. Prevalent heterophoria was assessed using cover un-cover and prism bar alternate cover testing at 33 cm and 6 m distance fixation. Cycloplegic autorefraction (1% cyclopentolate) was performed. Significant refractive error was defined as < or =-0.50SE and > or =+2.00SE. RESULTS Exophoria was highly prevalent at near fixation (age 6: 58.3%, age 12: 52.2%). Orthophoria predominated at distance fixation (age 6: 85.4%, age 12: 90.9%). Hyperopia was associated with esophoria at near (age 6: OR 1.7, 95% CI 1.1 to 2.8, age 12: OR 2.9, CI 1.1 to 2.8) and distance fixation (age 6: OR 9.7, CI 3.5 to 26, age 12: 9.6 OR, CI 4.2 to 22). Myopia was associated with exophoria at near (OR 2.1, CI 1.5 to 2.7) and distance fixation (OR 3.1, CI 2.1 to 4.4) for 12-year-old children only. Exophoria was more frequent in children of East Asian than European Caucasian origins, even after adjusting for refraction; at near (age 6: OR 1.4, CI 1.0 to 2.0, age 12: OR 1.4, CI 1.0 to 1.9) and distance (age 12: OR 1.7, CI 1.1 to 2.7). CONCLUSION Contrary to other studies, exophoria, not orthophoria, was predominant for near. Exophoria was more prevalent in children of East Asian origin. Longitudinal studies are needed to establish if incident heterotropia is preceded by heterophoria.