Maternal Lutein and Zeaxanthin Concentrations in Relation to Offspring Visual Acuity at 3 Years of Age: The GUSTO Study.

Lutein and zeaxanthin play important roles in visual functions, but their influence on early visual development is unclear. We related maternal lutein and zeaxanthin concentrations during pregnancy to offspring visual acuity (VA) in 471 mother-child pairs from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. Maternal concentrations of plasma lutein and zeaxanthin were determined at delivery. We measured uncorrected distance of VA in 3-year old children using a LEA Symbols chart; readings were converted to the logarithm of Minimum Angle of Resolution (logMAR), with >0.3 logMAR indicating poor VA. Associations were examined using linear or Poisson regression adjusted for confounders. The median (inter-quartile range) of maternal lutein and zeaxanthin concentrations were 0.13 (0.09, 0.18) and 0.09 (0.07, 0.12) µmol/L, respectively. A total of 126 children had poor VA. The highest tertile of maternal zeaxanthin concentration was associated with 38% lower likelihood of poor VA in children (95% CI: 0.42, 0.93, p-Trends = 0.02). Higher maternal lutein concentrations were associated with a lower likelihood of poor VA in children (RR 0.60 (95% CI: 0.40, 0.88) for middle tertile; RR 0.78 (95% CI: 0.51, 1.19) for highest tertile (p-Quadratic = 0.02)). In conclusion, lutein and zeaxanthin status during pregnancy may influence offspring early visual development; but the results require confirmation with further studies, including more comprehensive measurements of macular functions.

Case control study of risk factors and ophthalmological outcomes of very low birth weight infants with Type 1 retinopathy of prematurity.

INTRODUCTION: We evaluated the risk factors associated with Type 1 retinopathy of prematurity (ROP) in very low birth weight (VLBW) infants and compared ophthalmologic outcomes between cases with Type 1 ROP who received treatment and gestational age-matched controls with mild or no ROP not requiring treatment. METHODS: This was a retrospective case-control study of VLBW infants born in National University Hospital, Singapore, from January 2001 to December 2013. 17 cases with Type 1 ROP were each matched for gestational age with controls who had either mild (below Stage 2) or no ROP. Antenatal, perinatal and postnatal variables, as well as childhood ophthalmologic outcomes, were collected from their clinical records and analysed. RESULTS: The number of packed cell transfusions and highest fraction of inspired oxygen given at weeks 7-10 were found to be statistically significant on multivariate analysis (p = 0.045 and p = 0.049, respectively). None of the infants had blindness or retinal detachment, and there were no significant differences in refractive errors between the groups at 1-4 years of age. Strabismus at four years of age was more common in the group with Type 1 ROP (p = 0.023). CONCLUSION: Increased episodes of blood transfusions and chronic lung disease requiring high oxygen supplementation at 7-10 weeks of life are significant risk factors associated with Type 1 ROP in VLBW infants in our study. Strabismus at four years is more common in this group of patients. This study highlights the importance of long-term ophthalmologic surveillance for these high-risk children.

In-utero epigenetic factors are associated with early-onset myopia in young children.

OBJECTIVES: To assess whether epigenetic mechanisms affecting gene expression may be involved in the pathogenesis of early-onset myopia, we performed genome-wide DNA methylation analyses of umbilical cord tissues, and assessed any associations between CpG site-specific methylation and the development of the disorder when the children were 3 years old. METHODS: Genome-wide DNA methylation profiling of umbilical cord samples from 519 Singaporean infants involved in a prospective birth cohort 'Growing Up in Singapore Towards healthy Outcomes' (GUSTO) was performed using the Illumina Infinium HumanMethylation450K chip microarray. Multivariable logistic regression models were used to assess any associations between site-specific CpG methylation of umbilical cord tissue at birth and myopia risk in 3 year old children, adjusting for potential confounders. Gene expression of genes located near CpG sites that demonstrated statistically significant associations were measured in relevant ocular tissues using human and mouse fetal and adult eye samples. RESULTS: We identified statistically significant associations between DNA methylation levels at five CpG sites and early-onset myopia risk after correcting for multiple comparisons using a false discovery rate of 5%. Two statistically significant CpG sites were identified in intergenic regions: 8p23(p = 1.70×10-7) and 12q23.2(p = 2.53×10-7). The remaining 3 statistically significant CpG sites were identified within the following genes: FGB (4q28, p = 3.60×10-7), PQLC1 (18q23, p = 8.9×10-7) and KRT12 (17q21.2, p = 1.2×10-6). Both PQLC1 and KRT12 were found to be significantly expressed in fetal and adult cornea and sclera tissues in both human and mouse. CONCLUSIONS: We identified five CpG methylation sites that demonstrate a statistically significant association with increased risk of developing early-onset myopia. These findings suggest that variability in the neonatal cord epigenome may influence early-onset myopia risk in children. Further studies of the epigenetic influences on myopia risk in larger study populations, and the associations with adulthood myopia risk are warranted.

HOXA9 is a novel myopia risk gene.

PURPOSE: A recent meta-analysis revealed PAX6 as a risk gene for myopia. There is a link between PAX6 and HOXA9. Furthermore, HOXA9 has been reported to activate TGF-ß that is a risk factor for myopia. We speculate HOXA9 may participate in myopia development. METHODS: The Singapore GUSTO birth cohort provides data on children's cycloplegic refraction measured at age of 3 years and their methylation profile based on the umbilical cord DNA. The HOXA9 expression levels were measured in the eyes of mono-ocular form deprivation myopia in mice. The plasmid with the mouse HOXA9 cDNA was constructed and then transfected to mouse primary retinal pigment epithelial (RPE) cells. The expression levels of myopia-related genes and cell proliferation were measured in the HOXA9-overexpressed RPE cells. RESULTS: A total of 519 children had data on methylation profile and cycloplegic refraction. The mean spherical equivalent refraction (SE) was 0.90D. Among 8 SE outliers (worse than -2D), 7 children had HOXA9 hypomethylation. The HOXA9 levels in the retina of myopic eyes was 2.65-fold (p = 0.029; paired t-test) higher than the uncovered fellow eyes. When HOXA9 was over-expressed in the RPE cells, TGF-ß, MMP2, FGF2 and IGF1R expression levels were dose-dependently increased by HOXA9. However, over-expression of HOXA9 had no significant influence on IGF1 or HGF expression. In addition, HOXA9 also increased RPE proliferation. CONCLUSION: Based on the human, animal and cellular data, the transcription factor HOXA9 may promote the expression of pro-myopia genes and RPE proliferation, which eventually contribute to myopia development.

Diet and risk of myopia in three-year-old Singapore children: the GUSTO cohort.

BACKGROUND: To investigate the relationship between dietary intakes at six, nine and 12 months and risk of myopia in three-year-old children in a birth cohort. METHODS: Three hundred and seventeen children from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study were included. Dietary intake at six, nine and 12 months of age was ascertained using either 24-hour recalls or three-day food diaries completed by parents. Cycloplegia was achieved with three drops of one per cent cycloplentolate instilled at five minute intervals. Cycloplegic autorefraction and axial length (AL) were measured at three years of age with a table-mounted autorefractor and optical biometer, respectively. Myopia was defined as spherical equivalent (SE) of ≤ -0.50 D. Associations of dietary intake with SE, AL and myopia were examined by single dietary factor models using two multivariable regression models. Model 1 included adjusting for age, gender and total energy intake. Model 2 included additional adjustments for ethnicity, time spent outdoors, maternal education and parental myopia. RESULTS: In the single dietary factor adjusted models, dietary intakes at six, nine and 12 months were not associated with SE, AL and myopia. In model 1, protein, fat and carbohydrate intakes were not associated with SE, AL and myopia at any of the three time points (p > 0.05). In model 2, protein, fat and carbohydrate intakes were not associated with SE, AL and myopia at any of the three time points (p > 0.05). CONCLUSIONS: In this study, there was no evidence that diet at ages six, nine and 12 months was related to SE, AL or myopia at age three years. Further prospective studies with larger sample sizes are needed to understand the influence of diet on eye development in young children.

Is there a link between passive smoke exposure and early-onset myopia in preschool Asian children?

PURPOSE: To investigate the association of passive tobacco smoke exposure with early-onset myopia among three-year-old children in Singapore. METHODS: Pregnant mothers who attended their first trimester clinic at two major maternity units were recruited into the GUSTO birth cohort. The current analysis comprised 572 three-year-old children, who underwent cycloplegic autorefraction and axial length (AL) measurements. Myopia was defined as spherical equivalent (SE) of ≤-0.50 dioptres (D). Either parent completed questionnaires describing their child's exposure to passive smoke at six months, one and two years of age. RESULTS: There were 197 children (36.2%) who were exposed to passive smoke from birth to before six months. Compared to non-exposed children, children exposed to any passive smoke from birth to before six months experienced greater myopia prevalence (adjusted OR = 2.79; 95% CI: 1.24-6.29; p = 0.01). The odds of myopia in a child was greater if a smoker smokes at home, in the family car, or in the presence of the child (adjusted OR = 3.95; 95% CI: 1.41-11.09; p < 0.01) compared to non-exposed child. In contrast to myopia, childhood exposure to passive smoke did not systematically shift mean values for SE or AL. CONCLUSIONS: In this prospective birth cohort study, we found that childhood exposure to passive smoke from birth to before six months slightly increased the risk of early-onset myopia. This may indicate a delayed response to passive smoke exposure before six months and the development of myopia at three years of age. Our study is limited by the small number of myopic children at this young age. Thus, larger prospective studies using more objective cotinine level measures are required to fully establish and understand the influence of tobacco smoke on refractive development in older children.

The accuracy of anterior segment optical coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions.

PURPOSE: To evaluate the accuracy of the anterior segment optical coherence tomography (AS-OCT) in measuring the distance from the limbus to the insertion of primary and previously operated rectus muscles in children. METHODS: In this prospective, double masked, observational study the distance of the extraocular muscle insertion from the limbus measured by AS-OCT preoperatively was compared to intraoperative measurement using the surgical calipers. Consecutive patients 4-18 years of age undergoing primary or repeat strabismus surgery on horizontal or vertical rectus muscles between September 2013 and May 2014 were included. Patients with any condition that interfered with imaging were excluded. Participants were asked to look in the direction opposite to the muscle to ensure that the middle third of the muscle was being imaged and measured. RESULTS: A total of 65 muscles were evaluated, including 9 muscles undergoing reoperation and 10 vertical rectus muscles. Of these, 62 muscles were successfully imaged. In all reoperated eyes, the AS-OCT measurements were within 1 mm of the intraoperative measurements. Overall, 89.7% (95% CI, 78.8%-96.1%) of the measurements were within the 1 mm difference considered "clinically acceptable." The intraclass correlation coefficient comparing the reliability of the AS-OCT measurements with intraoperative measurements was 0.73 (95% CI, 0.53-0.85), or "good" agreement. CONCLUSIONS: AS-OCT can accurately detect rectus muscle insertions in primary or previously operated cases in children as young as 4 years of age.

Cyclic strabismus in adults.

Cyclic strabismus is a rare condition that usually occurs in children and is characterized by alternating intervals of straight and strabismic eyes. In adults with the condition, strabismus surgery often eliminates the cycles. We report a case of adult-onset cyclic esotropia that was converted into a cyclic exotropia.

Relative Contribution of Risk Factors for Early-Onset Myopia in Young Asian Children.

PURPOSE: To investigate the associations of near work, outdoor activity, and anthropometric risk factors with early-onset myopia in Singaporean preschool children. METHODS: Pregnant women who attended their first-trimester clinic at two major maternity units were recruited for the GUSTO birth cohort (n = 1236). Cycloplegic autorefraction and axial length (AL) were obtained in 3-year-old children (n = 572). Parents completed detailed questionnaires on parental myopia, near work, and outdoor activities when the child was 2 years of age. Height and weight were measured in the children at various time points from birth to 3 years of age. RESULTS: Among the cohort of 572 children, 35 children (6.1%) had early-onset myopia. In multivariable regression models, compared to children whose parents were not myopic, those with two myopic parents were more likely to have a more myopic spherical equivalent (SE) (regression coefficient: -0.36; 95% confidence interval [CI]: -0.61 to -0.11) and longer AL (regression coefficient: 0.24; 95% CI: 0.10-0.39) and more likely to have myopia (odds ratio [OR] = 4.8; 95% CI: 1.4-16.6). Neither near work nor outdoor activity was associated with SE, AL, and myopia. Taller children were found to have longer AL at birth and at 12, 24, and 36 months, but there were no associations with SE. CONCLUSIONS: Genetic factors may have a greater contribution to early development of refractive error compared to environmental factors.

A cluster randomised controlled trial evaluating an incentive-based outdoor physical activity programme to increase outdoor time and prevent myopia in children.

PURPOSE: To evaluate an incentive-based intervention to increase time spent outdoors among children in a 9-month cluster randomised controlled trial. METHODS: Two hundred and eighty-five children aged 6-12 years of age were randomised to the intervention (n = 147) or control arm (n = 138) in the Family incentive trial (FIT). The FIT intervention comprised of targeted education on myopia and good eye care habits, structured weekend outdoor activities and incentives for children to increase their daily steps via pedometers. The main outcome measure was outdoor time, measured by the WHO questionnaire and a 1-week diary. RESULTS: Interim analysis at 6 months showed a significant increase in mean outdoor time per week in the intervention arm (14.75 h week(-1) ) compared to the control arm (12.40 h week(-1) ) as measured by the questionnaire (p = 0.04). However, greater outdoor time was not statistically significant at the end of the trial (15.95 h week(-1) vs 14.34 h in the control group (p = 0.29). CONCLUSIONS: There was an increase in outdoor time for children in the incentive-based physical activity outdoor program after 6 months but not at the end of the trial. Further larger school trials with better compliance with the intervention and longer duration could be conducted to evaluate clinical outcomes such as myopic shifts.

A prospective comparison of chronic primary angle-closure glaucoma versus primary open-angle glaucoma in Singapore.

INTRODUCTION: To describe the optic disc, visual field and ocular characteristics of a consecutive cohort of Asian patients with chronic primary angle-closure glaucoma (CPACG), and compare them with those having primary open-angle glaucoma (POAG). METHODS: In a prospective comparative case series of new patients with POAG or CPACG in Singapore, all patients underwent visual acuity assessment, slit-lamp examination, tonometry, gonioscopy, refraction, Heidelberg Retina Tomograph (HRT) and Humphrey visual field (HVF) assessment. RESULTS: 98 patients were enrolled (POAG n = 48; CPACG n = 50). CPACG patients were significantly older (66.5 ± 9.2 years vs. 64.1 ± 13.5 years; p = 0.027) and mostly female (p = 0.004). CPACG eyes had significantly higher intraocular pressure (26.9 ± 6.9 mmHg vs. 24.5 ± 3.3 mmHg; p = 0.03), shorter axial length (22.89 ± 0.97 mm vs. 24.26 ± 1.79 mm; p < 0.001) and shallower anterior chamber depth (2.60 ± 0.25 mm vs. 3.16 ± 0.48 mm; p < 0.001). HVF mean deviation or pattern standard deviation (PSD) did not differ significantly between POAG and CPACG eyes, but the latter had a lower PSD for a given mean deviation. HRT parameters between the two groups were not significantly different. CONCLUSION: In this study, CPACG eyes had significantly higher presenting intraocular pressure than POAG eyes, but there were no significant differences in optic disc topography. A majority of the patients in both groups had moderate field defects at the time of presentation, followed by severe and then mild defects. The field loss in CPACG eyes was more diffuse than that in POAG eyes.

Quantitative assessment of changes in trabeculectomy blebs after laser suture lysis using anterior segment coherence tomography.

PURPOSE: To quantify changes in bleb morphology after laser suture lysis (LSL) using anterior segment optical coherence tomography (AS-OCT). PATIENTS AND METHODS: This was a prospective observational case series of patients who underwent trabeculectomy surgery with mitomycin-C and required subsequent LSL. Subjects were assessed before and immediately after LSL, and at 3 months after LSL. At each visit, a standardized cross-sectional AS-OCT image of the bleb was obtained, from which a masked observer measured bleb height (hB), cavity height (hC), wall cross sectional area (AW), cavity cross sectional area (AC), and bleb cross sectional area (AB) using custom software. RESULTS: Twenty-five subjects (25 eyes) were examined. LSL was performed at a mean of 21.5±16.3 days after trabeculectomy. Immediately after LSL, there was a significant increase in mean hB (P=0.026) and mean hC (P=0.45) from pre-LSL. At 3 months after LSL, there was a significant increase in mean hB (P=0.003), mean AC (P=0.047), and mean AB (P=0.006) as compared with before LSL. Increase in hB and hC immediately after LSL was predictive of outcome at month 3. CONCLUSIONS: AS-OCT was able to quantify changes in bleb morphology after LSL, some of which were predictive of eventual outcome.