Billy Heung Wing Chang

Association Between Body Composition and Retinal Vascular Caliber in Children and Adolescents

PURPOSE To elucidate the relationship between body composition and retinal vascular caliber (RVC) in children and adolescents. METHODS Participants aged 7 to 19 years were recruited from the Guangzhou Twin Eye Study cohort. Retinal vascular caliber was measured cross-sectionally from retinal images using a computer-aided program. The data were expressed as the central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE). Triceps skinfold thickness (TSFT) was measured using a skinfold caliper. Body composition was obtained through bioelectrical impedance analysis, providing fat mass (FM), fat mass index (FMI), fat-free mass (FFM), fat-free mass index (FFMI), body water mass (BWM), body water percentage (BWP), basal metabolic rate (BMR), and trunk fat percentage (TFP). RESULTS A total of 731 participants were included. Among the younger children (7-11 years), there was no significant association between body composition and RVC (all P > 0.05). However, for the older children (12-19 years), increasing FM, FMI, TFP, TSFT, and BMI were associated with CRAE negatively (β = -0.20, -0.68, -0.18, -0.17, and -0.48, respectively, all P < 0.05) and with CRVE positively (β = 0.47, 1.26, 0.34, 0.37, and 0.78, respectively, all P < 0.05), after adjusting for age, sex, axial length, mean arterial blood pressure, and the fellow vascular diameter. In contrast, increase in BWP was associated with larger CRAE (β = 0.33, P = 0.001) and smaller CRVE (β = -0.64, P < 0.001). Similar associations also were observed in the analyses when the body composition parameters were divided into quartiles (all P < 0.05). CONCLUSIONS In adolescents, greater body fat deposition is related to narrower retinal arterioles and wider retinal venules, and higher body water proportion is associated with retinal arterioles widening and retinal venules narrowing. Even during childhood, body composition might have an association with systemic microvasculature.

Cataract-Related Visual Impairment Corrected by Cataract Surgery and 10-Year Mortality: The Liwan Eye Study.

PURPOSE To assess 10-year mortality in people who had undergone cataract surgery with no residual visual impairment (VI) and those who had persistent VI due to cataract using a population-based cohort. METHODS The Liwan Eye Study is a 10-year longitudinal study commenced in 2003. According to the World Health Organization, presenting VI was defined as visual acuity less than 20/63 in the better-seeing eye. History of cataract surgery was defined as cataract surgery performed on either eye. Information on the date of surgery was recorded. Dates of death occurring between baseline and April 30, 2014 were obtained from the National Death Index data. Information on socioeconomic factors was obtained from questionnaire interviews. Cox proportional hazards regression models were used to assess the hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS Fifty-nine participants had undergone cataract surgery without residual VI and 67 participants had persistent cataract-related VI. The 10-year mortality rate for participants who had undergone cataract surgery without residual VI was statistically significant lower than that in participants who had VI due to cataract based on log-rank test (32.2% vs. 64.2%; P = 0.002). This finding remained significant in the unadjusted Cox proportional hazards model (HR, 0.43; 95% CI, 0.25-0.74; P = 0.002). After adjusting for age, sex, history of diabetes, and hypertension, body mass index (BMI), education level, and personal income, participants with cataract surgery and no residual VI did not have a higher chance of survival than participants with persistent VI due to cataract (HR, 0.56; 95% CI, 0.26-1.20; P = 0.136). CONCLUSIONS Cataract-related VI corrected by cataract surgery was not associated with better survival after adjusting for a number of possible confounders. Given our sample size is relatively small and limited power, further studies with larger sample are needed.

Does Myopia Affect Angle Closure Prevalence

PURPOSE To conduct a simulation study to estimate the prevalence of occludable angle (OA), a surrogate for primary angle closure glaucoma (PACG), with the increased rate of myopia in the Chinese population. METHODS People with phakic eyes in Liwan Eye Study were included as the study sample. Anterior chamber depth (ACD) was measured before dilation by A-mode ultrasound and OA was evaluated with static gonioscopy. Random sampling was used to generate 50 cohorts with sample size of 200 for each of myopic rates 10%, 20%, 40%, 50%, and 135 for myopic rate 60%, according to the multinomial distribution. The mean ACD and OA rates of each cohort were calculated. Logistic function model of nonlinear least-squares estimation was used to predict the prevalence of OA. RESULTS Data of the right eyes from 1160 subjects were qualified for analysis. The mean age was 64.2 ± 9.5 years, with 43% being male. The prevalence of myopia and OA was 32.5% (95% confidence interval [CI], 29.8%-35.3%) and 10.3% (95% CI, 8.7%-12.2%), respectively. The mean ACD in the sampling cohorts increased from 2.68 mm to 2.74 mm when the prevalence of myopia increased from 10% to 60%. The projected prevalence of OA in the cohorts with myopia prevalence of 10%, 20%, 40%, 50%, and 60% was 11.1% (95% CI, 10.5%-11.8%), 10.7% (95% CI, 10.1%-11.4%), 9.9% (95% CI, 9.3%-10.5%), 9.3% (95% CI, 8.8%-9.9%), and 9.6% (95% CI, 8.9-10.3%), respectively. CONCLUSIONS The increasing prevalence of myopia has minimal impact on the prevalence of OA.

Patterns in longitudinal growth of refraction in Southern Chinese children: cluster and principal component analysis

In the present study we attempt to use hypothesis-independent analysis in investigating the patterns in refraction growth in Chinese children, and to explore the possible risk factors affecting the different components of progression, as defined by Principal Component Analysis (PCA). A total of 637 first-born twins in Guangzhou Twin Eye Study with 6-year annual visits (baseline age 7–15 years) were available in the analysis. Cluster 1 to 3 were classified after a partitioning clustering, representing stable, slow and fast progressing groups of refraction respectively. Baseline age and refraction, paternal refraction, maternal refraction and proportion of two myopic parents showed significant differences across the three groups. Three major components of progression were extracted using PCA: “Average refraction”, “Acceleration” and the combination of “Myopia stabilization” and “Late onset of refraction progress”. In regression models, younger children with more severe myopia were associated with larger “Acceleration”. The risk factors of “Acceleration” included change of height and weight, near work, and parental myopia, while female gender, change of height and weight were associated with “Stabilization”, and increased outdoor time was related to “Late onset of refraction progress”. We therefore concluded that genetic and environmental risk factors have different impacts on patterns of refraction progression.