Amy Pai

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.

Ethnic differences in optic nerve head and retinal nerve fibre layer thickness parameters in children.

Aim To examine ethnic differences in optic nerve head and retinal nerve fibre layer (RNFL) parameters between European Caucasian and East Asian children aged 6–12 years. Methods Of 4118 children examined in the Sydney Childhood Eye Study (incorporating the Sydney Myopia Study) from 34 randomly selected primary and 21 secondary schools during 2003–5, 3382 (82.1%) had optical coherence tomography (OCT; Zeiss Stratus) data suitable for analysis. ‘Fast’ optic disc and RNFL scans were used. Ethnicity was defined only when both parents were of the same ethnicity. Results East Asian children tended to have a lower birth weight, were shorter with a smaller body mass index and were less hyperopic than European Caucasian children of the same age. After adjusting for age, gender, axial length, birth weight and optic-disc area, East Asian children had similar mean vertical disc diameters to European Caucasians (p=0.38, p=0.64 for 6–12 years, respectively) but 30–43% larger mean vertical cup diameters (p<0.0001 for both), resulting in larger mean cup/disc ratios (p<0.0001 for both). Compared with European Caucasians (101.95 μm and 104.57 μm, respectively), East Asian children had thicker mean average RNFL (105.45 μm and 107.92 μm, respectively; p=0.0006 and 0.0001) and thicker non-nasal RNFL quadrants in both ages. Conclusions Compared with European Caucasian children, East Asian children generally had thicker RNFL and larger mean cup/disc ratios. Given the relatively lower prevalence of open angle glaucoma in Asians, these anatomical variations could contribute to better understanding of apparent racial differences in glaucoma susceptibility.

Influence of OCT Signal Strength on Macular, Optic Nerve Head, and Retinal Nerve Fiber Layer Parameters

PURPOSE To examine the influence of different signal strengths on measurements made with optical coherence tomography (OCT) of macular, optic nerve head, and retinal nerve fiber layer (RNFL) parameters. METHODS From 2003 to 2005, 2092 children, mostly aged 12 years, were examined, and macular, optic nerve head, and RNFL parameters were measured by OCT. Multiple fast scans were acquired, and only right eyes were included in the analyses. Signal strength category was determined after averaging individual signal strengths from each scan and classifying scans as providing moderate (average signal strength, 5-7.49), good (average signal strength, 7.5-9.49), and excellent (average signal strength, >or=9.5) image quality. General linear models were used after adjustment for covariates. RESULTS Significant differences were observed between measurements obtained at excellent signal strengths compared with those obtained at moderate and good signal strengths for both macular and optic nerve parameters. However, although statistically significant, the magnitude of the differences in macular parameters was very small (approximately 5 microm, or a 2% difference). Differences in optic nerve head parameters were much greater (up to a 32% difference), with larger measurements recorded for most parameters with increasing signal strength category. Significant differences in RNFL parameters with increasing signal strength were not demonstrated. CONCLUSIONS Significantly larger macular and optic nerve head OCT measurements were obtained with increasing signal strength measurements, although absolute differences in macular measurements were small and are of questionable clinical importance. The results support the robustness of OCT in providing precise macular imaging.

Prevalence and risk factors for visual impairment in preschool children the sydney paediatric eye disease study.

PURPOSE To assess the prevalence and associations of visual impairment (VI) in preschool children. DESIGN Cross-sectional, population-based study. PARTICIPANTS A total of 2461 children (73.8% participation rate), aged 6 to 72 months, were examined in the Sydney Paediatric Eye Disease Study during 2007-2009; of whom 1188, aged 30 to 72 months, with complete visual acuity (VA) data in both eyes, were included in this report. METHODS Measurement of VA was attempted on all children using the Electronic Visual Acuity (EVA) system or a logarithm of the minimum angle of resolution (logMAR) chart. Visual impairment was defined as presenting VA <20/40 in children aged ≥48 months and <20/50 in those aged <48 months. Post-cycloplegic refraction was measured, and myopia was defined as spherical equivalent (SE) ≤-0.50 diopters (D), hyperopia was defined as SE ≥2.00 D, astigmatism was defined as cylinder ≥1.00 D, and anisometropia was defined as SE difference ≥1.00 D between 2 eyes. Ethnicity, birth parameters, and sociodemographic information were collected in questionnaires completed by parents. MAIN OUTCOME MEASURES Visual impairment prevalence and its associations with child demographic factors and birth parameters. RESULTS Visual impairment was found in 6.4% of the worse eye and 2.7% of the better eye in our sample. Refractive errors (69.7%) and amblyopia (26.3%) were the principal causes of VI in the worse eye. Astigmatism (51.3%) and hyperopia (28.9%) were the main refractive errors causing VI. In regression analysis controlling for other factors, VI was independently associated with low birthweight of <2500 g (odds ratio 2.4, 95% confidence interval, 1.1-5.3), but not with age, gender, ethnicity, or measures of socioeconomic status (P > 0.05). CONCLUSIONS Visual impairment in at least 1 eye was found in 6.4% of Australian preschool children, with bilateral VI found in 2.7%. Uncorrected refractive errors and amblyopia were the principal ocular conditions associated with VI. Low birthweight was a significant risk factor independent of age, gender, and ethnicity. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Impact of Ethnicity on the Correlation of Retinal Parameters with Axial Length

PURPOSE To examine whether the relationship of axial length (AL) to retinal nerve fiber layer (RNFL) and macular parameters measured by optical coherence tomography (OCT) differs according to ethnicity. METHODS As part of the Sydney Myopia Study, 2353 children from grade 7 (age range, 11.1-14.4 years) completed detailed ocular examinations in the 2004-2005 school year. AL was measured with noncontact interferometry and Stratus OCT was performed (Carl Zeiss Meditec, Jena, Germany). RESULTS East Asian children displayed larger AL correlations with average RNFL, inferior RNFL, nasal RNFL, outer macula, and macular volume (r = -0.25, -0.36, -0.31, -0.35, and -0.31 respectively; P < 0.001) than did Caucasian children (r = -0.14, -0.20, -0.12, -0.17, and -0.13 respectively; P < 0.001). Positive correlations between the temporal RNFL and AL were found only among East Asian and South Asian children (r = 0.28, P < 0.001; and r = 0.27, P = 0.03, respectively). In Caucasian children, the foveal minimum and central macula correlated significantly with AL (r = 0.11 and r = 0.13, respectively, P ≤ 0.001). CONCLUSIONS Retinal parameters measured by OCT correlated with AL, and the extent of this correlation varied by ethnicity. It may therefore be that ethnicity should be considered when interpreting OCT scans on individuals with AL outside the usual range.

Measurement of Optic Nerve Head Parameters: Comparison of Optical Coherence Tomography With Digital Planimetry

PurposeTo compare the measurements of optic nerve head parameters from digital photographic images and optical coherence tomography (OCT) in normal children. MethodsThe Sydney Childhood Eye Study assessed 1765 children aged 6 years from 34 randomly selected primary schools during 2003 to 2005. Optic nerve head parameters were measured from digital photographs captured using a Canon fundus camera (CF-60Uvi)/EOS 10D and OCT3 (Zeiss Stratus) using the “fast” optic disc protocol. Retinal images of 333 sequential child participants were graded using both methods and are included in analyses. Optic disc and cup area, vertical and horizontal disc and cup diameters, vertical and horizontal cup/disc diameter ratios, and cup/disc area ratios were calculated using both modalities. Magnification of the planimetric images was corrected using the Bengtsson formula. ResultsMean vertical and horizontal disc and cup diameter and mean disc and cup area, as measured using OCT (1.76, 1.50, 0.71, and 0.68 mm and 2.15 and 0.47 mm2, respectively) were significantly (P<0.0001; cup area P=0.0014) smaller than when measured using digital photography (1.85, 1.66, 0.76, and 0.74 mm and 2.40 and 0.51 mm2, respectively). All 3 cup/disc ratio measures did not vary significantly (P>0.05) between the 2 methods (0.41, 0.45, and 0.22 vs. 0.41, 0.44, and 0.21, respectively). ConclusionsLinear and area measures by Stratus-OCT, compared with digital planimetry measurements, are around 10% smaller; however, all 3 cup/disc ratios were preserved. Where OCT produces unexpectedly small cup/disc ratios, manual viewing is advisable. However, OCT can be considered moderately reliable in measuring and monitoring cup/disc ratio in clinical settings.

Relationship between Retinal Structures and Retinal Vessel Caliber in Normal Adolescents

PURPOSE To describe the normal physiological relationship between retinal arteriolar and venular caliber and retinal nerve fiber layer (RNFL), macular, and optic nerve head parameters. METHODS The Sydney Childhood Eye Study assessed 2038 adolescents aged 12 years. Retinal vessel calibers were measured from digital fundus photographs using standardized protocols. Optical coherence tomography measurements of RNFL, macular, and optic nerve head parameters were obtained with the Fast-scan protocol of the Stratus OCT (Carl Zeiss Meditec, Inc., Dublin, CA). Mixed model analyses were performed. RESULTS After adjustment for covariates, each micrometer increase in RNFL thickness was associated with a 0.22-microm (0.15%, P < 0.0001) and 0.49-microm (0.23%, P < 0.0001) increase in mean arteriolar and venular caliber, respectively. This positive association existed across all RNFL quadrants (0.07%-0.24%, P <or= 0.002). Each micrometer increase in macular thickness (inner/outer) and cubic millimeter increase in macular volume was associated with a 0.12/0.15-microm (0.08%-0.10%, P < 0.0001) and 5.31-microm (3.53%, P < 0.0001) increase in mean arteriolar caliber and a 0.22/0.31-microm (0.10%-0.15%, P < 0.0001) and 10.95-microm (5.08%, P < 0.0001) increase in mean venular caliber, respectively. Finally, each millimeter increase in vertical optic disc diameter and each square millimeter increase in optic disc area was associated with a 2.83-microm (1.88%, P = 0.02) and 2.02-microm (1.35%, P = 0.01) increase in mean retinal arteriolar caliber and a 5.73-microm (2.66%, P = 0.001) and 5.02-microm (2.33%, P < 0.0001) increase in mean retinal venular diameter, respectively. CONCLUSIONS In normal adolescent retinas, thicker RNFL and macula parameters and larger optic discs correlate with larger retinal vascular caliber. Understanding these normal anatomic relationships is essential for determining their significance in studying the vascular etiology of ocular and systemic diseases.

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.

Complement Factor H and the Bilaterality of Age-Related Macular Degeneration: The Blue Mountains Eye Study

OBJECTIVE To determine whether complement factor H (CFH Y402H) genotype influences bilateral involvement of age-related macular degeneration (AMD) lesions. METHODS The Blue Mountains Eye Study (BMES) followed up 3654 participants 49 years and older (BMES 1, 1992-1994), including 2335 (75.3% of survivors) at the 5-year (BMES 2, 1997-1999) and 1952 (76.5%) at the 10-year (BMES 3, 2002-2004) examinations. Age-related macular degeneration retinal photographic grading used the Wisconsin system. Early and late AMD included prevalent and incident cases from all visits. CFH genotyping used TaqMan assays. RESULTS Of 767 AMD cases, 53.3% of early and 53.1% of late AMD cases were bilateral. After adjusting for age and other covariants, the CFH CC (Y402H polymorphism) genotype was associated with an increased likelihood of bilateral compared with unilateral involvement by any soft drusen (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.4-4.5), distinct soft drusen (OR, 2.8; 95% CI, 1.0-8.1), and pigmentary abnormalities (OR, 1.7; 95% CI, 1.0-2.8). We could not establish significant associations between this genotype and the bilaterality of late AMD (OR, 1.8; 95% CI, 0.4-7.7), either geographic atrophy (OR, 0.6; 95% CI, 0.07-4.6) or neovascular AMD (OR, 3.4; 95% CI, 0.3-41.4). CONCLUSIONS Persons with the CFH CC genotype at any given age have an increased likelihood of bilateral compared with unilateral involvement of some early AMD lesions.

Characteristics and appearance of the normal optic nerve head in 6-year-old children

Aim To document planimetric measures of normal optic nerve head parameters in 6-year-old children and to report prevalence and associations of common optic nerve signs. Methods The Sydney Childhood Eye Study examined 1765 children aged 6 years. Complete retinal photographs were available for 1225 participants, captured using a digital camera. Optical coherence tomography optic-disc measurements were acquired using the ‘fast’ optic-disc protocol. Statistical analyses were conducted using SAS version 9.1.3. Results The mean (95% CIs) planimetric optic-disc area was 2.29 mm2 (2.27 to 2.32), mean cup area 0.48 mm2 (0.47 to 0.50), mean vertical disc diameter 1.81 mm (1.80 to 1.82) and mean vertical cup diameter 0.72 mm (0.71 to 0.73), resulting in a mean vertical cup/disc ratio of 0.40 (0.39 to 0.40). Similarities existed between vertical, horizontal and area cup/disc ratios (p>0.05) measured by planimetry and optical coherence tomography, but only for vertical disc diameters between 1.75 and 1.96 mm. Visible lamina cribrosa pores were present in 4.9%. This sign was associated with larger optic nerve parameters. The prevalence of optic disc tilt and cyclotorsion was 1.6% and 8.7%, respectively, and the prevalence of α- and β-peripapillary atrophy was 43.3% and 20.2%, respectively. Neither sign was associated with myopia, after adjusting for age, sex and ethnicity, although eyes with β-peripapillary atrophy had a longer mean axial length (p=0.04). Cilioretinal arteries were present in 27% and tended to be located temporally. Conclusions The mean vertical cup/disc ratio was 0.4 in this 6-year-old sample. Planimetric optic nerve head measures and population prevalence findings for optic disc signs in this population could be regarded as normative data for ophthalmologists in clinical settings.