Cheryl Ngo

Comparison of measurements of time outdoors and light levels as risk factors for myopia in young Singapore children

AimsTo compare methods to measure time outdoor and light levels, two possible predictors of myopia, in Singapore children.MethodsOutdoor time from a diary and portable light meter over a 1-week period was compared in 117 Singapore children aged 6–12 years with and without myopia. All children wore a (HOBO Pendant temp/light Part # UA-002-64) light meter for 1 week and the parents filled the 7-day outdoor diary to track the outdoor activity.ResultsMean outdoor time from diary and time with light levels was 5.44 hours per week and 7.91 hours per week, respectively, during school term and school holidays. Time spent with light levels of >1000 Lux from the light meter were 7.08 h per week and 9.81 h per week, respectively, during school term and school holidays. The intraclass correlation coefficients were 0.21 and 0.28 for outdoor time from the diary and light meter (1000 Lux cut-off) during the school term and holidays, respectively. The correlation coefficient was 0.34 (95% CI 0.05, 0.58) for a weekday during school holidays, 0.17 (−0.14, 0.45) for a weekday during school term, 0.07 (−0.16, 0.29) for a weekday during school term, and 0.25 (0.02, 0.46) for a weekend during school term.ConclusionsThe agreement between the light meter and 1-week diary was poor to fair. Both instruments measure different parameters, time outdoors and light intensity, and could therefore capture different aspects of risk in future myopia studies.

Changes in retinal nerve fibre layer, optic nerve head morphology, and visual field after acute primary angle closure

Aims/PurposeTo determine and correlate the long-term changes in retinal nerve fibre layer (RNFL) thickness, optic nerve head (ONH) morphology, and visual fields after a single episode of acute primary angle closure (APAC).MethodsThis was a cross-sectional comparative study of patients at National University Hospital (Singapore) from 2000 to 2006 after an episode of unilateral APAC. The peripapillary and macular RNFL were measured using Stratus optical coherence tomography (OCT) and ONH configuration was assessed using Heidelberg Retina Tomography (HRT)-III. Humphrey perimetry was also performed, and the presence of disc pallor was noted. APAC eyes were compared with fellow eyes as matched controls.ResultsTwenty-five patients were assessed at a median of 33 months (range, 11–85 months) after APAC. OCT showed that there was a reduction in the peripapillary and outer macular RNFL thickness in APAC eyes compared with controls. Humphrey perimetry revealed significantly reduced mean deviation (P=0.006) and increased pattern standard deviation (P=0.045) in APAC eyes compared with controls. HRT-III showed no difference in mean rim area, rim volume, or cup–disc ratio between APAC eyes and controls. Disc pallor was present in nine APAC eyes (36%) but was absent in fellow eyes (P=0.002), and was associated with peripapillary RNFL thinning, visual field loss, and an increased interval between the onset of symptoms and normalization of intraocular pressure (P=0.023).ConclusionAPAC results in peripapillary and outer macular RNFL loss, visual field defects, and optic disc pallor, even in cases in which the ONH configuration remains unchanged.

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

To evaluate an incentive‐based intervention to increase time spent outdoors among children in a 9‐month cluster randomised controlled trial.

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

PurposeTo quantify changes in bleb morphology after laser suture lysis (LSL) using anterior segment optical coherence tomography (AS-OCT). Patients and MethodsThis 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. ResultsTwenty-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. ConclusionsAS-OCT was able to quantify changes in bleb morphology after LSL, some of which were predictive of eventual outcome.

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.

Does sunlight (bright lights) explain the protective effects of outdoor activity against myopia

In the following point‐counterpoint article, internationally‐acclaimed myopia researchers were challenged to defend the two opposing sides of the topic defined by the title; their contributions, which appear in the order, Point followed by Counterpoint, were peer‐reviewed by both the editorial team and an external reviewer. Independently of the invited authors, the named member of the editorial team provided an Introduction and Summary, both of which were reviewed by the other members of the editorial team. By their nature, views expressed in each section of the Point‐Counterpoint article are those of the author concerned and may not reflect the views of all of the authors.

Visual Acuity Outcomes with SA60D3, SN60D3, and ZM900 Multifocal IOL Implantation After Phacoemulsification

PURPOSE To assess the near and distance visual acuity achieved with implantation of the ReSTOR SA60D3 and SN60D3 (Alcon Laboratories Inc) and Tecnis ZM900 (Abbott Medical Optics [AMO]) multifocal intraocular lens (IOL) after cataract surgery. METHODS This is a retrospective study of 108 eyes of 54 patients who underwent uneventful bilateral phacoemulsification of cataract and IOL implantation at an ophthalmic center in Singapore by a single surgeon. Inclusion criteria were visually significant cataracts, corneal astigmatism <2.00 diopters, and no other ocular diseases. Patients received the SA60D3, SN60D3, or ZM900 multifocal IOL in both eyes. Binocular near and distance visual acuity outcomes were assessed 3 months after second-eye surgery. RESULTS No difference in mean postoperative uncorrected and best spectacle-corrected visual acuity for distance among the groups was noted. The ZM900 lens was significantly better than both ReSTOR lenses for uncorrected near vision with 96.7% achieving N5 compared to 75% of SA60D3 patients and 83.3% of SN60D3 patients (P=.003). For distance corrected near vision, 100% of ZM900 patients achieved N5 compared to 83.3% for each the SA60D3 and SN60D3 IOLs (P=.005). No significant difference between both ReSTOR lenses for near vision was noted. CONCLUSIONS All three IOLs provide similar uncorrected and best corrected distance visual acuity. However, the ZM900 IOL provides better binocular distance corrected and uncorrected near acuity than the SA60D3 or SN60D3. The ZM900 IOL group was more myopic preoperatively compared to the other two groups, which may be a contributing factor.

Eye size and shape in newborn children and their relation to axial length and refraction at 3 years

To determine if eye size and shape at birth are associated with eye size and refractive error 3 years later.

Macular Ganglion Cell and Retinal Nerve Fiber Layer Thickness in Children With Refractive Errors—An Optical Coherence Tomography Study

Purpose: To study the distribution of macular ganglion cell-inner plexiform layer (GC-IPL) thickness and peripapillary retinal nerve fiber layer (RNFL) thickness in children with refractive errors. Materials and Methods: Two hundred forty-three healthy eyes from 139 children with refractive error ranging from −10.00 to +5.00 D were recruited from the National University Hospital Eye Surgery outpatient clinic. After a comprehensive ocular examination, refraction, and axial length (AL) measurement (IOLMaster), macular GC-IPL and RNFL thickness values were obtained with a spectral domain Cirrus high definition optical coherence tomography system (Carl Zeiss Meditec Inc.). Only scans with signal strength of >6/10 were included. Correlation between variables was calculated using the Pearson correlation coefficient. A multivariate analysis using mixed models was done to adjust for confounders. Results: The mean spherical equivalent refraction was −3.20±3.51 D and mean AL was 24.39±1.72 mm. Average, minimum, superior, and inferior GC-IPL were 82.59±6.29, 77.17±9.65, 83.68±6.96, and 81.64±6.70 &mgr;m, respectively. Average, superior, and inferior peripapillary RNFL were 99.00±11.45, 123.20±25.81, and 124.24±22.23 &mgr;m, respectively. Average, superior, and inferior GC-IPL were correlated with AL (&bgr;=−2.056, P-value 0.000; &bgr;=−2.383, P-value 0.000; &bgr;=−1.721, P-value 0.000), but minimum GC-IPL was not (&bgr;=−1.056, P-value 0.115). None of the RNFL parameters were correlated with AL. Conclusions: This study establishes normative macular GC-IPL and RNFL thickness in children with refractive errors. Our results suggest that high definition optical coherence tomography RNFL parameters and minimum GC-IPL are not affected by AL or myopia in children, and therefore warrants further evaluation in pediatric glaucoma patients.

Axial Length/Corneal Radius of Curvature Ratio and Myopia in 3-Year-Old Children.

Purpose This study investigated the association of axial length (AL) to corneal radius of curvature (CRC) ratio with spherical equivalent (SE) in a 3-year old Asian cohort. Methods Three-hundred forty-nine 3-year old Asian children from The Growing Up in Singapore towards Healthy Outcomes (GUSTO) birth cohort study underwent AL and CRC measurements with a noncontact ocular biometer and cycloplegic refraction using an autorefractor. The ratio of AL to CRC (AL/CRC) was calculated for all the participants, and subsequently AL, CRC, and AL/CRC were analyzed in relationship to SE. Results The SE showed better correlation with AL/CRC (Spearmans correlation coefficient, ρ = −0.53; 95% confidence interval [CI]: −0.66; −0.49; P < 0.001) compared to either AL or CRC alone ([ρ = −0.36; 95% CI: −0.51 to 0.51; P = 0.01] and [ρ = 0.05; 95% CI: −0.04 to 0.17; P = 0.34], respectively). Mean AL/CRC was 2.91 ± 0.06 among myopes and decreased to 2.79 ± 0.06 among hyperopes. Axial length to corneal radius of curvature was strongly correlated with SE in myopes (ρ = −0.78; 95% CI: −3.76; −0.79; P = < 0.001), but not in emmetropes and hyperopes ([ρ = −0.39; 95% CI: −10.73; −0.57; P = 0.01] and [ρ = −0.18; 95% CI: −17.28; 12.42; P = 0.38], respectively). Linear regression adjusted for gender and ethnicity showed a 0.74-diopter shift in SE towards myopia with every 0.1 increase in AL/CRC ratio (P < 0.001, r2 = 0.33). Conclusion The correlation between SE and AL/CRC is stronger than that between AL or CRC alone. This suggests that in a research setting, when cycloplegic refraction is difficult to perform on 3-year-old children, AL/CRC may be the next best reference for refractive error. Translational Relevance In the research setting, AL/CRC may be the next best reference for refractive error over AL alone when cycloplegic refraction is unavailable in 3-year old children.