Central corneal thickness and intraocular pressure in Kenya

Abstract

Title: Central Corneal thickness and intraocular pressures in Kenya. Objective: The main objective of this study was to establish the central corneal thickness in selected Kenyan communities. Rationale: Studies done in Caucasians and African Americans suggest that Africans have thinner central corneas and this leads to an underestimation of intraocular pressures. Hence patients may end up not receiving appropriate , treatment with subsequent glaucomatous damage and loss of vision that might have been avoidable. Statement of the Problem: Intraocular pressure is an essential eiement in the management of glaucoma. CCT has been identified as a potential source of error in the measurement of lOP (1-2). Estimates of intraocular pressure by applanation tonometry are influenced by CCT. We assume and apply a specific value for CCT in applanation tonometry estimates as the Goldmann equation is based on theoretical calculations accurate at CCT of 520 micrometers. However, there lS compelling evidence that CCT varies between individuals, with ethnicity. Failure to adjust lOP estimates of variation In CCT influences clinical decision-making. The underestimation of lOP due to thin cornea may delay the diagnosis and treatment of glaucoma. There is also the risk of pseudoocular hypertensive patients being subjected to inappropriate treatment in cases 0 f thicker CCT (3) The measurement of CCT may playa role in the clinical evaluation of lOP with a baseline CCT to be obtained for patients with suspected glaucoma. The American Academy of Ophthalmology (J) reports that this recommendation presents Ophthalmologists with a dilemma: there is no single formula to recalculate lOP as the relationship between CCT and lOP is not linear and there is no accepted universal algorithm (2, 25). Methodology: A total of261 eyes of 132 patients were examined. Three patients had only one eye included in the study as their contralateral eyes had corneal pathologies. Three hospitals with eye units were selected representing three major ethnic groups in Kenya: that is Sabatia Hospital, Litein AlC Mission Hospital and Isiolo District Hospital - had their Central Corneal Thickness, Goldmann .. Applanation Tonometry and Schioetz Indentation Tonometry readings where applicable. Results: A total of 261 eyes of 132 patients were analyzed for CCT, GAT and SIT. There were 71 males (54%) and 61 female (46%) respectively. Bantus contributed ,143, Nilotes 90 and Cushites 28. Using Levene's Test for Equality of Variance. P was 0.013 at a mean difference of± 15.54. This is statistically insignificant and variation in sample numbers did not affect the fmal results ofCCT, GAT and SIT. The mean CCT was 521.43 micrometers, with a GAT mean of 15.04mmHg and a SIT mean of 14.393mmHg. This mean CCT of 521.43 micrometers is lower than that established by other studies of 555-573 micrometers. (3,9,20,35, 38,4J,42,44). The mean CCT for the three ethnic groups were 521.76, 524.72 and 509.18 micrometers respectively. Weighted t-test correlations showed no statistical significance.