ABSTRACT
PURPOSE: To evaluate the measurement of optic disc morphology using Heidelberg Retinal Tomography (HRT) with and without the aid of optic disc photos. METHODS: One hundred three children (aged 11 and 12 y, 52 boys) were selected randomly from the Singapore Cohort study of Risk Factors for Myopia. Optic nerve head topography and retinal nerve fiber layer thickness measurements were assessed using the HRT-II (Heidelberg, Germany) scanning laser ophthalmoscope. All contour lines were drawn by the same researcher on 2 occasions. The first drawing was made without optic disc photographs but using the 3-dimensional rotation assessment. The second drawing was made with the additional aid of digital monoscopic optic disc photographs. RESULTS: There was a high correlation between the measurements taken with and without optic disc photographs. For the global disc area, the difference between the mean readings was 0.67 mm and the intraclass correlation (ICC) was 0.81 [95% confidence interval (CI) 0.73-0.86]. The mean difference for the global cup-to-disc ratio was 0.03 [ICC 0.86 (95% CI 0.80-0.90)]. The ICCs were high across almost all of the readings except rim volume, in which the ICC was 0.57 (95% CI 0.43-0.69). CONCLUSIONS: This study shows minimal differences in HRT measured optic disc parameters when optic disc photos are used to aid in the definition of the scleral ring. Omitting the use of disc photographs in measuring HRT outputs may translate into significant savings in time and logistics in simultaneously obtaining HRT and optic disc photographs in large population-based studies.
Subject(s)
Diagnostic Techniques, Ophthalmological , Glaucoma/diagnosis , Nerve Fibers/pathology , Optic Disk/pathology , Photography , Retinal Ganglion Cells/pathology , Child , Female , Humans , Male , Myopia/diagnosis , Myopia/etiology , Ophthalmoscopy/methods , Risk Factors , Tomography/methodsABSTRACT
PURPOSE: X-linked red-green colour blindness is the most common form of colour blindness. Various studies suggest that, worldwide, 2-8% of men are afflicted with this condition. The purpose of this study is to determine the prevalence of red-green colour blindness in Singaporean schoolchildren. METHOD: A total of 1249 children aged 13-15 years were screened using the Ishihara 24-plate edition book during the School Cohort study of the Risk factors for Myopia visit. RESULTS: A total of 1210 children (96.8%) managed to correctly identify at least 13 of the initial 15 plates and were deemed to have normal colour vision.Thirty-three children (32 boys, one girl) were only able to identify nine or less plates and were considered to be colour blind. Overall, 5.4% (95% confidence interval 3%, 7%) of Chinese, 4.9% (1%, 9%) of Malay and 4.9% (2%, 11%) of Indian boys were colour blind (P = 0.97). Classification plates 16-17 were useful in determining deutran or protan tendencies in only 14 (43%) of the 33 children identified as being colour blind. CONCLUSION: 5.3% of boys and 0.2% of girls were found to be colour blind in this Singapore-based study. Although the Ishihara test proved useful in identifying colour-blind children, other tests are required to accurately classify the types of red-green colour blindness in these children.
Subject(s)
Color Vision Defects/epidemiology , Adolescent , Asian People/statistics & numerical data , Chromosomes, Human, X , Cohort Studies , Color Vision Defects/diagnosis , Color Vision Defects/ethnology , Color Vision Defects/genetics , Diagnostic Techniques, Ophthalmological , Female , Genetic Linkage , Humans , India/ethnology , Male , Prevalence , Sex Distribution , Singapore/epidemiologyABSTRACT
PURPOSE: To determine corneal biomechanical parameters measured with the Reichert Ocular Response Analyser (ORA) in Singaporean children, and to assess their possible correlations with refractive error and biometry. METHODS: This was a cross-sectional study of 271 subjects from the Singapore Cohort Study of Risk Factors for Myopia (SCORM). Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), and cornea-compensated intraocular pressure (IOPcc) were measured with the ORA. Spherical equivalent refraction was assessed with an autokeratorefractometer and axial length by contact ultrasound A-scan biometry. Height, weight, and blood pressure were measured. RESULTS: The mean age of the study population was 13.97 +/- 0.89 years, the distribution of the sexes was almost equal (138 boys, 50.9%), and most were Chinese (186 subjects, 68.6%). The mean (+/-SD) CH and CRF were 11.78 +/- 1.55 (range, 6.93-16.53) and 11.81 +/- 1.71 (range, 7.83-16.83) mm Hg. CH and CRF did not vary significantly with age (P = 0.24; 0.61), sex (P = 0.21; 0.08), or race (P = 0.23; 0.36). CH and CRF did not vary with myopia status (P = 0.79; 0.83) or axial length (Pearson correlation coefficient [r] = -0.11 and -0.05, P = 0.08 and 0.40). Multivariate analyses were performed with CH, CRF, or CCT as the dependent variable and age, sex, race, weight, IOPcc, CCT, SE refraction, and corneal curvature as covariates. CH was significantly associated with IOP (regression coefficients [beta] = -0.22 [95% confidence interval = -0.27 to -0.17]), CCT (beta = 0.03 [0.02-0.03]) and corneal curvature (beta = -1.13 [-2.08 to -0.19]). CRF was significantly associated with IOP, CCT, and corneal curvature (beta = 0.08 [0.02-0.14]; 0.03 [0.03-0.04], and -1.39 [-2.54 to -0.23], respectively). The only factor that was predictive of decreased CCT was Malay or Indian race (P = 0.03 and <0.001), compared with Chinese. CONCLUSIONS: The CH and CRF values in our study on Singaporean children are slightly higher than in adult studies. CH and CRF are not associated with refractive error or axial length. Flatter corneas are associated with lower CH and CRF readings.
