Central corneal thickness and its association with ocular and general parameters in Indians: the Central India Eye and Medical Study.
ABSTRACT To evaluate the distribution of central corneal thickness (CCT) and its associations in an adult Indian population.
The Central India Eye and Medical Study is a population-based study performed in a rural region close to Nagpur in Central India; it included 4711 subjects (ages 30+ years) of 5885 eligible subjects (response rate, 80.1%).
The participants underwent a detailed ophthalmic and medical examination, including 200 standardized questions on socioeconomic background, lifestyle, social relations, and psychiatric depression. This study was focused on CCT as measured by sonography and its associations. Intraocular pressure was measured by applanation tonometry.
Central corneal thickness and intraocular pressure.
Central corneal thickness measurement data were available on 9370 (99.4%) eyes. Mean CCT was 514+/-33 microm (median, 517 microm; range, 290-696 microm). By multiple regression analysis, CCT was associated significantly with younger age (P<0.001), male gender (P<0.001), higher body mass index (P = 0.006), lower corneal refractive power (P<0.001), deeper anterior chamber (P = 0.02), thicker lens (P = 0.02), and shorter axial length (P = 0.006). Central corneal thickness was not associated significantly with refractive error (P = 0.54) or cylindrical refractive error (P = 0.20). If eyes with a corneal refractive power of 45 or more diopters were excluded, the relationship between CCT and axial length was no longer statistically significant (P>0.05), whereas all other relationships remained significant. Intraocular pressure readings increased significantly (P<0.001) with both higher CCT and higher corneal refractive power.
Indians from rural Central India have markedly thinner corneas than do Caucasians or Chinese, and, as in other populations, CCT is greater in men. CCT was associated with younger age, higher body mass index, lower corneal refractive power, deeper anterior chamber, thicker lens, and shorter axial length. Intraocular pressure readings were associated with CCT, with high readings in those eyes that had thick corneas or steep corneas. Central corneal thickness and steepness of the anterior corneal surface may thus both have to be taken into account when applanation tonometry is performed.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Article: Central corneal thickness, intraocular pressure, and degree of myopia in an adult myopic population aged 20 to 40 years in southeast Spain: determination and relationships.[show abstract] [hide abstract]
ABSTRACT: To determine the values of, and study the relationships among, central corneal thickness (CCT), intraocular pressure (IOP), and degree of myopia (DM) in an adult myopic population aged 20 to 40 years in Almeria (southeast Spain). To our knowledge this is first study of this kind in this region. An observational, descriptive, cross-sectional study was done in which a sample of 310 myopic patients (620 eyes) aged 20 to 40 years was selected by gender- and age-stratified sampling, which was proportionally fixed to the size of the population strata for which a 20% prevalence of myopia, 5% epsilon, and a 95% confidence interval were hypothesized. We studied IOP, CCT, and DM and their relationships by calculating the mean, standard deviation, 95% confidence interval for the mean, median, Fisher's asymmetry coefficient, range (maximum, minimum), and the Brown-Forsythe's robust test for each variable (IOP, CCT, and DM). In the adult myopic population of Almeria aged 20 to 40 years (mean of 29.8), the mean overall CCT was 550.12 μm. The corneas of men were thicker than those of women (P = 0.014). CCT was stable as no significant differences were seen in the 20- to 40-year-old subjects' CCT values. The mean overall IOP was 13.60 mmHg. Men had a higher IOP than women (P = 0.002). Subjects over 30 years (13.83) had a higher IOP than those under 30 (13.38) (P = 0.04). The mean overall DM was -4.18 diopters. Men had less myopia than women (P < 0.001). Myopia was stable in the 20- to 40-year-old study population (P = 0.089). A linear relationship was found between CCT and IOP (R(2) = 0.152, P ≤ 0.001). CCT influenced the IOP value by 15.2%. However no linear relationship between DM and IOP, or between CCT and DM, was found. CCT was found to be similar to that reported in other studies in different populations. IOP tends to increase after the age of 30 and is not accounted for by alterations in CCT values.Clinical Ophthalmology 01/2011; 5:249-58.
Article: Ethnic and mouse strain differences in central corneal thickness and association with pigmentation phenotype.[show abstract] [hide abstract]
ABSTRACT: The cornea is a transparent structure that permits the refraction of light into the eye. Evidence from a range of studies indicates that central corneal thickness (CCT) is strongly genetically determined. Support for a genetic component comes from data showing significant variation in CCT between different human ethnic groups. Interestingly, these studies also appear to show that skin pigmentation may influence CCT. To validate these observations, we undertook the first analysis of CCT in an oculocutaneous albinism (OCA) and Ugandan cohort, populations with distinct skin pigmentation phenotypes. There was a significant difference in the mean CCT of the OCA, Ugandan and Australian-Caucasian cohorts (Ugandan: 517.3±37 µm; Caucasian: 539.7±32.8 µm, OCA: 563.3±37.2 µm; p<0.001). A meta-analysis of 53 studies investigating the CCT of different ethnic groups was then performed and demonstrated that darker skin pigmentation is associated with a thinner CCT (p<0.001). To further verify these observations, we measured CCT in 13 different inbred mouse strains and found a significant difference between the albino and pigmented strains (p = 0.008). Specific mutations within the melanin synthesis pathway were then investigated in mice for an association with CCT. Significant differences between mutant and wild type strains were seen with the nonagouti (p<0.001), myosin VA (p<0.001), tyrosinase (p = 0.025) and tyrosinase related protein (p = 0.001) genes. These findings provide support for our hypothesis that pigmentation is associated with CCT and identifies pigment-related genes as candidates for developmental determination of a non-pigmented structure.PLoS ONE 01/2011; 6(8):e22103. · 4.09 Impact Factor
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ABSTRACT: To determine the mean values for central corneal thickness (CCT) and intraocular pressure (IOP) and the relationship between these values, in healthy Malay children to serve as reference values in diagnosis and treatment. A cross-sectional study. One hundred and eight eyes (54 subjects) of Malay children without diagnosis of ocular abnormality or disease meeting our inclusion and exclusion criteria were selected. The CCT and IOP were measured by specular microscopy and non-contact air-puff tonometry respectively, for analysis and comparison with the values obtained in previous studies. Mean CCT and IOP was found to be 530.87 ± 30.79 µm and 15.65 ± 3.05 mm Hg respectively. CCT was found not to vary with age. A positive relationship was found between CCT and IOP; specifically, with every 100-µm increase in CCT, IOP increased by 3.5 mm Hg. CCT and IOP are strongly related in healthy Malay children aged 8 to 16. The mean CCT of Malay children is lower than that of majority children of other ethnic groups, supporting the existence of CCT variation among different populations and that ethnicity should be a key consideration when applying CCT data to the general pediatric population.PLoS ONE 01/2011; 6(10):e25208. · 4.09 Impact Factor