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.
"It showed that the axial myopia associated thinning of the sclera was located predominantly posterior to the equator and increased in proximity to the posterior pole of the eye. Correspondingly, scleral thickness measurements at or posterior to the equator were not significantly correlated with corneal thickness measurements, fitting with clinical studies in which central corneal thickness was not related with axial length . Since due to geometric reasons, the globe elongation is associated with an increase in scleral surface area, it was unclear whether despite the scleral thinning, the scleral cross sectional area and scleral volume also decreased or even increased. "
[Show abstract][Hide abstract] ABSTRACT: To examine whether the scleral cross sectional area and estimated scleral volume are associated with a longer axial length in human eyes.
Histologic anterior-posterior sections running through the pupil and the optic nerve head were examined. Using a light microscope, we measured the thickness of the sclera at the limbus, ora serrata, equator, midpoint between equator and posterior pole (MPEPP), peripapillary region and posterior pole. Additionally we determined the length and the cross section area of the sclera.
The histomorphometric study included 214 human globes of 214 subjects (mean age: 62.5±13.9 years) (147 eyes enucleated due to malignant choroidal melanoma or due to other non-glaucomatous reasons; 67 eyes enucleated due to secondary angle-closure glaucoma). Mean axial length was 25.1±1.8 mm (median: 24.0 mm; range: 20-35 mm). Scleral thickness measurements decreased with increasing axial length for values taken at the equator (P = 0.008; correlation coefficient r = -0.18), MPEPP (P<0.001;r:-0.47), optic nerve head border (P<0.001;r = -0.47) and posterior pole (P<0.001;r = -0.54). Scleral cross section area decreased significantly with increasing axial lengths for the regions at or behind the equator (P = 0.002;r = -0.21), at or behind the MPEPP (P = 0.001;r = -0.25), and at or behind the optic nerve head border (P = 0.001;r = -0.24). Scleral volume measurements were not significantly associated with axial length.
Despite an associated increase in surface area, eyes with longer axial length do not have an increase in scleral volume. It may point against a scleral volume enlargement to play a role in the process of axial elongation.
PLoS ONE 03/2014; 9(3):e93551. DOI:10.1371/journal.pone.0093551 · 3.23 Impact Factor
"In our study, we found a central corneal thickness of 536 um in the normal control group. A meta-analysis of corneal thickness literature done previously had found that the mean central corneal thickness in normal white adults was 535 um, whereas a study done in rural central India found a mean central corneal thickness of 514 um, which was thinner compared to our values. Studies done on this topic previously have found significant inter-racial variation in central corneal thickness. "
[Show abstract][Hide abstract] ABSTRACT: Studies mainly in the western population have compared central corneal thickness in primary open angle glaucoma and normal individuals have found variable results. We did this study to compare the central corneal thickness of primary open angle glaucoma patients with normal controls in a south Indian population.
This was a masked, cross-sectional study undertaken in a tertiary care center in South India. A total of 50 controls and 50 primary open angle glaucoma patients were studied. Central corneal thickness between the two groups was compared using Wilcoxon two sample test and the signed rank test.
The mean central corneal thickness in the control group was 536 μm (462-608 μm) and in the primary open angle glaucoma group was 531 μm (476-609 μm).
There was no significant difference in the central corneal thickness between primary open angle glaucoma patients and the normal controls.
Oman Journal of Ophthalmology 03/2013; 6(1):33-6. DOI:10.4103/0974-620X.111907
"In comparison to other ethnic groups, the Ugandan mean CCT of 517.3 µm was considerably thin and was the lowest measurement found in any African study performed using ultrasound (see Table S1). Only three studies performed with ultrasound have observed a lower CCT than that found in the Ugandans, with two of these from Australian Aboriginal cohorts and the other from an Indian population –. Consequently, the meta-analysis revealed that Australian Aboriginals have the lowest CCT measurements of any ethnic group, although the smaller number of participants assessed in this population suggests that further investigation is required to confirm this finding. The ethnic group with the second lowest CCT measurements as determined by the meta-analysis were the South Asians, which comprised predominately of Indians, followed by African natives, South East Asians and African migrants, indicating that the populations with the darkest skin pigmentation also had the lowest CCT measurements. "
[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 08/2011; 6(8):e22103. DOI:10.1371/journal.pone.0022103 · 3.23 Impact Factor
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