Publications by authors named "Carol Y L Cheung"

6 Publications

  • Page 1 of 1

High prevalence of myopia in children and their parents in Hong Kong Chinese Population: the Hong Kong Children Eye Study.

Acta Ophthalmol 2020 Jan 24. Epub 2020 Jan 24.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong.

Purpose: To determine the myopia prevalence in Hong Kong Chinese children and their parents.

Methods: It was a population-based cross-sectional study. A total of 4257 children aged 6-8 years, and 5880 parents were recruited in the Hong Kong Children Eye Study. Cycloplegic autorefraction was measured for children; and non-cycloplegic autorefraction for parents. Parental educational level, children's outdoor time, and near work were collected by validated questionnaires.

Results: In children aged 6-8 years, 25.0% were myopic, and among them, 12.7% for the 6-year-olds, 24.4% for the 7-year-olds and 36.1% for the 8-year-old. About 0.7% of children aged 8 years were high myopia. In all age groups, boys (their myopia rate: 13.9% at 6 years, 26.7% at 7 years, and 38.3% at 8 years) were more myopic than girls (11.3% at 6 years, 22.0% at 7 years, 33.4% at 8 years). Among parents, 72.2% were myopic (mother, 73.2%; father, 70.7%) and 13.5% high myopia (mother, 12.8%; father, 14.5%). It was observed that prevalence decreased with ages and increased with education level.

Conclusion: There is a strikingly high prevalence of myopia in Hong Kong children aged 6-8, much higher than that of other regions of China. Of note, the prevalence of children was similar to that in 15 years ago. Furthermore, the myopia prevalence of parents is high, and it had already increased in this cohort. Prevention of childhood myopia is important, likewise for visual complications from high myopia in adults.
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January 2020

Cup-to-Disc Ratio From Heidelberg Retina Tomograph 3 and High-Definition Optical Coherence Tomography Agrees Poorly With Clinical Assessment.

J Glaucoma 2016 Feb;25(2):198-202

*Singapore Eye Research Institute & Singapore National Eye Center †Duke-NUS Graduate Medical School ‡Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.

Purpose: To investigate the agreement of vertical cup-to-disc ratio (VCDR) measured from Heidelberg Retina Tomograph 3 (HRT-3), high-definition optical coherence tomography (HD-OCT), and clinical grading.

Methods: A total of 933 consecutive subjects underwent optic nerve head imaging with HRT-3 and HD-OCT during a single visit. The vertical dimensions of the disc and cup were measured by slit-lamp examination using an eyepiece graticule. Bland-Altman plots evaluated the agreement in the VCDR obtained by the 2 instruments and clinical grading.

Results: We found a significant trend for the difference in VCDR measured clinically and with HRT and HD-OCT (P<0.001 for both). The mean VCDR differed significantly between clinical measurement and that evaluated by HRT and HD-OCT, respectively (0.40 ± 0.12 vs. 0.37 ± 0.21 and 0.40 ± 0.12 vs. 0.50 ± 0.14, P<0.001 for both), with significantly poor correlation (r(2)=0.35 and 0.34, P<0.001 for both).

Conclusions: In general, there is poor correlation and a lack of agreement of VCDR measured using HRT-3, HD-OCT, and clinical grading. HD-OCT has somewhat better agreement with clinical measurements of VCDR. Compared with clinical grading, HD-OCT tended to overestimate VCDR, whereas HRT-3 tended to underestimate it.
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February 2016

Prevalence of cognitive impairment in Chinese: epidemiology of dementia in Singapore study.

J Neurol Neurosurg Psychiatry 2013 Jun 5;84(6):686-92. Epub 2013 Feb 5.

Department of Pharmacology, National University of Singapore, Singapore.

Objective: To study the prevalence of and associated factors for cognitive impairment and dementia in community dwelling Chinese from Singapore.

Methods: This study includes Chinese subjects from the Epidemiology of Dementia in Singapore (EDIS) study, aged ≥60 years, who underwent comprehensive examinations, including cognitive screening with the locally validated Abbreviated Mental Test and Progressive Forgetfulness Questionnaire. Screen positive participants subsequently underwent extensive neuropsychological testing and cerebral MRI. Cognitive impairment no dementia (CIND) and dementia were diagnosed according to internationally accepted criteria. The prevalence of cognitive impairment and dementia were computed per 5 year age categories and gender. To examine the relationship between baseline associated factors and cognitive impairment, we used logistic regression models to compute odd ratios with 95% CI.

Results: 1538 Chinese subjects, aged ≥60 years, underwent cognitive screening: 171 (15.2%) were diagnosed with any cognitive impairment, of whom 84 were CIND mild, 80 CIND moderate and seven had dementia. The overall age adjusted prevalence of CIND mild was 7.2%; CIND moderate/dementia was 7.9%. The prevalence increased with age, from 5.9% in those aged 60-64 years to 31.3% in those aged 75-79 years and 44.1% in those aged ≥80 years. Multivariate analysis revealed age, diabetes and hyperlipidaemia to be independently associated with cognitive impairment.

Conclusions: In present study, the overall prevalence of cognitive impairment and dementia in Chinese was 15.2%, which is in the same range as the prevalence reported in Caucasian and other Asian populations.
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June 2013

Influence of height, weight, and body mass index on optic disc parameters.

Invest Ophthalmol Vis Sci 2010 Jun 13;51(6):2998-3002. Epub 2010 Jan 13.

Singapore Eye Research Institute, Singapore National Eye Center, Singapore.

Purpose: To examine the influence of body height, body weight, and body mass index (BMI) on optic disc parameters in a population-based study.

Methods: The Singapore Malay Eye Study examined 3280 persons of Malay ethnicity, aged 40 to 80 years, of whom 2329 (71.0%) had reliable retinal scanning confocal laser tomography images for analyses. Intraocular pressure (IOP) was ascertained by Goldmann applanation tonometry. Body height and weight were measured with standardized protocols; BMI was calculated as weight (kilograms)/height squared (meters). Sociodemographic information was collected in an interviewer-administered questionnaire.

Results: In univariate analyses, body height, weight, and BMI were significantly associated with optic cup area, rim area, and cup-to-disc area ratio (all with P < 0.05) but none of the anthropometric parameters was significantly associated with optic disc area (all with P > 0.05). In multiple regression analyses after adjustment for age, sex, optic disc size, axial length, education, family income, and IOP, each SD increase in body height was associated with a 0.042-mm(2) decrease in optic rim area and a 0.020 increase in optic cup-to-disc area ratio; each SD decrease in body weight was associated with a 0.013-mm(2) decrease in optic rim area and a 0.010 increase in optic cup-to-disc ratio; and each SD decrease in BMI was associated with a 0.021-mm(2) decrease in optic rim area and a 0.010 increase in optic cup-to-disc ratio.

Conclusions: Persons who are taller or have lower BMI have a smaller neuroretinal rim area and a larger optic cup-to-disc area ratio.
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June 2010

Descemet stripping endothelial keratoplasty: effect of the surgical procedure on corneal optics.

Am J Ophthalmol 2008 Jun 14;145(6):991-6. Epub 2008 Mar 14.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong, People's Republic of China.

Purpose: To determine the changes in corneal optical performance after posterior lamellar corneal transplantation.

Design: Retrospective case series.

Methods: The anterior segment in four eyes of four patients who underwent Descemet stripping endothelial keratoplasty (DSEK) with cataract extraction and intraocular lens (IOL) implantation were imaged with the Visante anterior segment optical coherence tomography [OCT] (Carl Zeiss Meditec, Dublin, California, USA). The curvature of the posterior surface of the donor graft was compared with that of the host cornea, and corneal thickness was measured.

Results: All eyes had a hyperopic refractive error after surgery. The posterior corneal curvature after surgery was more than that before surgery. Average preoperative keratometry was 43.4 diopters (D), and after surgery, it was 42.8 D using keratometry. However, when the postsurgical corneal power was calculated using the Gaussian optics method, the average value was 40.8 D.

Conclusions: The addition of a donor corneal graft to the posterior surface of decompensated corneas may lessen the effective optical power of the cornea and may have implications for IOL power calculations in these eyes.
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June 2008

Agreement among 3 methods to measure corneal thickness: ultrasound pachymetry, Orbscan II, and Visante anterior segment optical coherence tomography.

Ophthalmology 2007 Oct 15;114(10):1842-7. Epub 2007 May 15.

Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong, China.

Purpose: To assess the agreement of central and paracentral corneal thickness measurements between ultrasound pachymetry (USP), Orbscan II, and Visante anterior segment optical coherence tomography (ASOCT).

Design: Observational cross-sectional study.

Participants: Seventy eyes of 70 subjects.

Methods: Each subject underwent Orbscan II (using an acoustic equivalent correction factor of 0.89), ASOCT, and USP examination. Bland-Altman plots were used to evaluate agreement between instruments.

Main Outcome Measures: Central and paracentral corneal thickness measurements by the 3 methods and agreement, as evaluated by 95% limits of agreement (LOA).

Results: The mean measurements of average central corneal thickness by USP, Orbscan II, and ASOCT were 553.5+/-30.26 microm, 553.22+/-25.47 microm, and 538.79+/-26.22 microm, respectively. There was high correlation between instruments: USP with ASOCT (r = 0.936, P<0.001), USP with Orbscan II (r = 0.900, P<0.001) for central corneal thickness measurements, and Orbscan II with ASOCT for average paracentral 2- to 5-mm measurements (r = 0.947, P<0.001). The mean differences (and upper/lower LOA) for central corneal thickness measurements were 0.31+/-13.34 microm (26.44/-25.83) between USP and Orbscan II, 14.74+/-10.84 microm (36.0/-6.51) between USP and ASOCT, and 14.44+/-9.14 microm (32.36/-3.48) between Orbscan II and ASOCT. The average mean difference (and upper/lower LOA) between Orbscan II and ASOCT for paracentral 2- to 5-mm corneal thickness measurements was 10.35+/-8.67 microm (27.35/-6.65).

Conclusion: Anterior segment optical coherence tomography underestimated corneal thickness compared with that measured with USP. Anterior segment optical coherence tomography had better agreement with the gold standard USP, as compared with Orbscan II. However, important discrepancies among instruments exist. Clinicians should be aware that corneal thickness measurements are influenced by the method of measurement and that, although highly correlated, these instruments should not be used interchangeably for the assessment of corneal thickness.
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October 2007