Annette Kifley

Outdoor Activity Reduces the Prevalence of Myopia in Children

OBJECTIVE To assess the relationship of near, midworking distance, and outdoor activities with prevalence of myopia in school-aged children. DESIGN Cross-sectional study of 2 age samples from 51 Sydney schools, selected using a random cluster design. PARTICIPANTS One thousand seven hundred sixty-five 6-year-olds (year 1) and 2367 12-year-olds (year 7) participated in the Sydney Myopia Study from 2003 to 2005. METHODS Children had a comprehensive eye examination, including cycloplegic refraction. Parents and children completed detailed questionnaires on activity. MAIN OUTCOME MEASURES Myopia prevalence and mean spherical equivalent (SE) in relation to patterns of near, midworking distance, and outdoor activities. Myopia was defined as SE refraction < or = -0.5 diopters (D). RESULTS Higher levels of outdoor activity (sport and leisure activities) were associated with more hyperopic refractions and lower myopia prevalence in the 12-year-old students. Students who combined high levels of near work with low levels of outdoor activity had the least hyperopic mean refraction (+0.27 D; 95% confidence interval [CI], 0.02-0.52), whereas students who combined low levels of near work with high levels of outdoor activity had the most hyperopic mean refraction (+0.56 D; 95% CI, 0.38-0.75). Significant protective associations with increased outdoor activity were seen for the lowest (P = 0.04) and middle (P = 0.02) tertiles of near-work activity. The lowest odds ratios for myopia, after adjusting for confounders, were found in groups reporting the highest levels of outdoor activity. There were no associations between indoor sport and myopia. No consistent associations between refraction and measures of activity were seen in the 6-year-old sample. CONCLUSIONS Higher levels of total time spent outdoors, rather than sport per se, were associated with less myopia and a more hyperopic mean refraction, after adjusting for near work, parental myopia, and ethnicity.

Role of near work in myopia: findings in a sample of Australian school children.

PURPOSE To examine the association of time spent in near work and reading with spherical equivalent refraction (SER) in a population-based sample of 12-year-old Australian schoolchildren. METHODS Data on the time spent in near-work or outdoor activities per week and estimates for the duration of continuous reading and reading distances, were collected in questionnaires (2353 participants, 75.3% response) in the Sydney Myopia Study between 2004 and 2005; 2339 children underwent a comprehensive eye examination, including cycloplegia. RESULTS Longer time spent on reading for pleasure and reports of close reading distance (< 30 cm) were associated with a more myopic refraction after adjustment for age, sex, ethnicity, and school type (P(trend) = 0.02 and P = 0.0003, respectively). Time spent in individual near-work activities, however, correlated poorly with SER (all r < or = 0.2) and was not significant in multivariate analyses for myopia (SER < or = -0.50 D), with adjustment for age, sex, ethnicity, parental myopia, school type, and outdoor activity. Children of European Caucasian ethnicity reported spending marginally less time in near work than children of East Asian ethnicity (26.0 h/wk vs. 32.5 h/wk, P < 0.0001). East Asian ethnicity, however, was associated with substantially greater odds of having myopia (odds ratio [OR], 11.0; 95% confidence interval [CI], 7.0-17.4). Near work such as close reading distance (< 30 cm) and continuous reading (> 30 minutes) independently increased the odds of having myopia in this sample of children. CONCLUSIONS Although myopia was not significantly associated with time spent in near work after adjustment for other factors, there were significant independent associations with close reading distance and continuous reading. These associations may indicate that the intensity rather than the total duration of near work is an important factor.

Ethnic differences in refraction and ocular biometry in a population-based sample of 11-15-year-old Australian children

PurposeTo examine the prevalence of refractive error and distribution of ocular biometric parameters among major ethnic groups in a population-based sample of 11–15-year-old Australian children.MethodsThe Sydney Myopia Study examined 2353 students (75.3% response) from a random cluster-sample of 21 secondary schools across Sydney. Examinations included cycloplegic autorefraction, and measures of corneal radius of curvature, anterior chamber depth, and axial length.ResultsParticipants mean age was 12.7 years (range 11.1–14.4); 49.4% were female. Overall, 60.0% of children had European Caucasian ethnicity, 15.0% East Asian, 7.1% Middle Eastern, and 5.5% South Asian. The most frequent refractive error was mild hyperopia (59.4%, 95% confidence interval (CI), 53.2–65.6), defined as spherical equivalent (SE) +0.50 to +1.99 D. Myopia (SE−0.50 D or less) was found in 11.9%, 95% (CI 6.6–17.2), and moderate hyperopia (SE⩾+2.00 D) in 3.5%, 95% (CI 2.8–4.1). Myopia prevalence was lower among European Caucasian children (4.6%, 95% CI 3.1–6.1) and Middle Eastern children (6.1%, 95% CI 1.3–11.0) than among East Asian (39.5%, 95%, CI 25.6–53.5) and South Asian (31.5%, 95%, CI 21.6–41.4) children. European Caucasian children had the most hyperopic mean SE (+0.82 D) and shortest mean axial length (23.23 mm). East Asian children had the most myopic mean SE (−0.69 D) and greatest mean axial length (23.86 mm).ConclusionThe overall myopia prevalence in this sample was lower than in recent similar-aged European Caucasian population samples. East Asian children in our sample had both a higher prevalence of myopia and longer mean axial length.

Sensory and Cognitive Association in Older Persons: Findings from an Older Australian Population

Background: Explanations for associations found between sensory and cognitive function remain unclear. Objective: To assess in an older Australian population: (1) the correlation between sensory and cognitive function across groups with a narrow age range; (2) any independent association between sensory and cognitive impairment. Methods: We examined 3,509 non-institutionalised residents aged 50+ years in the second cross-sectional survey of the Blue Mountains Eye Study (1997–2000). Visual impairment was defined for best-corrected visual acuity (VA) <6/12 in the better eye, moderate to severe hearing loss for hearing threshold >40 dB (better ear), and likely cognitive impairment for Mini-Mental State Examination (MMSE) <24 points. Results: We found likely cognitive impairment in 3.3%, vision impairment in 2.7% and moderate to severe hearing loss in 10.5% of this population. Correlation between VA or hearing threshold and MMSE score increased with age. After adjusting for age, weak but significant correlation was evident in the normal ageing sample between vision and MMSE (r = 0.12 with vision items included and r = 0.11 with vision items excluded, both p < 0.0001), and between hearing thresholds and MMSE (r = –0.12, p < 0.0001). After adjusting for age, sex, education and history of stroke, persons with vision impairment had a lower mean MMSE score than those with normal vision, regardless of whether vision-related items were included (27.1 vs. 28.6, p < 0.001) or excluded (19.8 vs. 21.0, p < 0.001). Similarly, persons with moderate to severe hearing loss had a lower mean MMSE score than those without hearing loss (28.1 vs. 28.7, p < 0.001). Persons with likely cognitive impairment also had lower mean VA and higher mean hearing threshold than those without, after adjustment. Conclusions: We have documented an age-related correlation between sensory and cognitive function in a normal ageing sample. The association between sensory impairment and likely cognitive impairment remained significant after excluding vision-related MMSE items and adjusting for confounding factors. Our data suggest that age-related decline and the effect of visual impairment on the measurement of cognition only partly explain the association between sensory and cognitive impairments in older persons.

Prevalence and associations of anisometropia and aniso-astigmatism in a population based sample of 6 year old children

Aim: To study the distribution of anisometropia and aniso-astigmatism in young Australian children, together with clinical and ocular biometry relations. Method: The Sydney Myopia Study examined 1765 predominantly 6 year old children from 34 randomly selected Sydney schools during 2003–4. Keratometry, cycloplegic autorefraction, and questionnaire data were collected. Results: Spherical equivalent (SE) anisometropia (⩾1 dioptre) prevalence was 1.6% (95% confidence interval (CI) 1.1% to 2.4%). Aniso-astigmatism (⩾1D) prevalence was 1.0% (CI: 0.6% to 1.6%). Both conditions were significantly more prevalent among moderately hyperopic (SE ⩾2.0D) than mildly hyperopic (SE 0.5–1.9D) children. Myopic children (SE ⩽−0.5D) had higher anisometropia prevalence. Neither condition varied by age, sex, or ethnicity. In multivariate analyses, anisometropia was significantly associated with amblyopia, odds ratio (OR) 29, (CI: 8.7 to 99), exotropia (OR 7.7, CI: 1.2 to 50), and neonatal intensive care unit (NICU) admission (OR 3.6, CI: 1.1 to 12.6). Aniso-astigmatism was significantly associated with amblyopia (OR 8.2, CI: 1.4 to 47), maternal age >35 years (OR 4.0, CI: 1.3 to 11.9), and NICU admission (OR 4.6, CI: 1.2 to 17.2). Anisometropia resulted from relatively large interocular differences in axial length (p<0.0001) and anterior chamber depth (p = 0.0009). Aniso-astigmatism resulted from differences in corneal astigmatism (p<0.0001). Conclusion: In this predominantly 6 year old population, anisometropia and aniso-astigmatism were uncommon, had important birth and biometry associations, and were strongly related to amblyopia and strabismus.

Five-year incidence and progression of vascular retinopathy in persons without diabetes: the Blue Mountains Eye Study.

PurposeTo assess the 5-year incidence of vascular retinopathy and its associations in an older nondiabetic population.MethodsThe Blue Mountains Eye Study examined 3654 residents aged 49+ years (82.4% response rate) during 1992–1994, and re-examined 2335 (75.1% of survivors) during 1997–1999. Retinopathy lesions (microaneurysms, haemorrhages, hard or soft exudates) were assessed from 6-field retinal photographs in persons without diabetes. Incident retinopathy was assessed in those at risk. Hypertensive status was defined following the WHO/International Society of Hypertension guidelines.ResultsOf the 2335 re-examined, 195 had retinopathy lesions at baseline and 1725 were at risk of retinopathy after excluding subjects with diabetes (n=261), retinal vein occlusion (n=52) or missing/un-gradable photographs (n=102). The cumulative 5-year incidence was 9.7% (95% confidence intervals (CI) 8.3–11.1%). Age was the only factor significantly associated with incident retinopathy (Pfor trend=0.012). Neither fasting blood glucose (age–sex-adjusted P=0.147) nor hypertension (adjusted Pfor trend=0.43) was associated with incident retinopathy. Of the 195 with retinopathy lesions at baseline, 3.5% developed diabetes, 13.3% progressed, and 72.3% regressed/disappeared over 5 years. Progression was positively associated with elevated blood pressure (BP) (adjusted odds ratio (OR) 1.3, 95% CI 1.1–1.6 per 10 mmHg systolic BP) and inversely associated with fasting glucose level (OR 0.36, CI 0.14–0.92 per mmol/l increase). Aspirin use was weakly associated with regression (OR 2.4, CI 1.0–6.0).ConclusionsOver 5 years, retinopathy developed in 10% of older people without diabetes, while 72% of baseline lesions regressed. Age was significantly associated with the development of these lesions.

Relation of age-related macular degeneration and cognitive impairment in an older population.

Background: The aetiology of age-related macular degeneration (AMD) and cognitive impairment is poorly understood. A link between cognitive impairment and AMD has been proposed although only a weak association was found in population-based studies. Purpose: To assess cross-sectional associations between AMD and cognitive impairment in an older Australian population. Methods: The Blue Mountains Eye Study examined 3,509 persons aged 49+ years during 1997–2000. AMD lesions were assessed from retinal photographs using the Wisconsin System. Mini-mental state examination (MMSE), demographics, lifestyle factors and medical history were collected at interview. MMSE score was categorised as high-normal (28–30), low-normal (24–27) and impaired (<24). A modified MMSE excluded five vision related items and was dichotomised as normal (18–22) and impaired (0–17). Logistic regression was used to assess associations after adjusting for age, sex, visual impairment, stroke, current smoking status, hypertension, alcohol consumption and post-high-school qualification. Results: Prevalence rates for late and early AMD were 1.5% (n = 50) and 8.3% (n = 273), respectively. Cognitive impairment was present in 18.0% in persons with late AMD and 8.4% with early AMD, compared to 2.6% in persons without AMD. After multivariate adjustment, late AMD was associated with low normal MMSE (odds ratio (OR): 2.2, 95% confidence interval (CI): 1.1–5.0) and cognitive impairment (OR: 3.7, CI: 1.3–10.6). Using the modified MMSE, the multivariate association between late AMD and cognitive impairment remained (OR: 2.2, CI: 1.0–5.0). No significant association was found between cognitive impairment and early AMD. Conclusions: We found a significant, cross-sectional association between late AMD and cognitive impairment in a sample of older Australians that appeared to be independent of visual impairment. The association was weaker but remained significant after excluding vision-related items from the MMSE.

Retinal Vascular Caliber and the Long‐Term Risk of Diabetes and Impaired Fasting Glucose: The Blue Mountains Eye Study

Objective: To assess the associations of retinal vessel caliber with the 10‐year incidence of diabetes and impaired fasting glucose (IFG). Methods: The Blue Mountains Eye Study is a population based cohort study of Australian residents aged at least 49 years, with baseline examinations conducted during 1992–4. Retinal arteriolar and venular calibers were measured and summarized from baseline digitized images in 3368 participants. Diabetes was defined as a physician‐diagnosis of diabetes or fasting blood glucose ≥ 126 mg/dL and IFG as fasting blood glucose 109 to 125 mg/dL. Ten year incidence of diabetes and IFG was defined from 5‐ and 10‐year follow up data. Results: After adjusting for age and gender, wider retinal venular caliber was associated with an increased incidence of diabetes and IFG. These associations were not significant after controlling for baseline glucose, body mass index and other factors. In persons 49–70 years of age at baseline, however, the association of wider retinal venular caliber and incident IFG persisted after further controlling for other factors (OR, 1.53, 95% CI, 1.11–2.12). Retinal arteriolar caliber was not associated with incident diabetes or IFG. Conclusions: This study suggests that wider retinal venular caliber was associated with higher risk of IFG in middle‐aged persons.

Influence of physical activity and screen time on the retinal microvasculature in young children.

Objective—It is not clear whether physical activity and sedentary behavior affect retinal microvascular caliber. We investigated associations among physical activity (outdoor and indoor sporting activities), sedentary behaviors (including screen time, television [TV] viewing, and computer and videogame usage), and retinal microvascular caliber in schoolchildren. Methods and Results—Six-year-old students (1765/2238) from a random cluster sample of 34 Sydney schools were examined. Parents completed questionnaires about physical and sedentary activities. Retinal images were taken, and retinal vessel caliber was quantified. After adjusting for age, sex, ethnicity, eye color, axial length, body mass index, birth weight, and mean arterial blood pressure, children who spent more time in outdoor sporting activities (in the highest tertile of activity) had 2.2 &mgr;m (95% CI 0.65 to 3.71) wider mean retinal arteriolar caliber than those in the lowest tertile (Ptrend=0.004). Increasing quartiles of time spent watching TV were associated with narrower mean retinal arteriolar caliber ≈2.3 &mgr;m (95% CI 0.73 to 3.92), Ptrend=0.003. Conclusion—These data suggest that physical activity could have a beneficial influence, whereas screen time has a potential adverse influence on retinal microvascular structure. The magnitude of arteriolar narrowing associated with each hour daily of TV viewing is similar to that associated with a 10-mm Hg increase in systolic blood pressure in children.

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.