Assessment of the Role of Central Corneal Thickness in Measuring the Intra-ocular Pressure in the Screening for Glaucoma amongst People Residing in a Sub-Himalayan Territory of North India

Abstract

Aims: To find out the average central corneal thickness (CCT) and intraocular pressure (IOP) and to determine the prevalence of ocular hypertension in the study group. Methods: It was a cross sectional study conducted on subjects with age more than 30 years. These respondents were subjected to Visual acuity, IOP measurement using hand held Perkins applanation tonometer (PAT), measurement of central corneal thickness using ultrasonic hand held pachymeter and fundus evaluation was done using direct ophthalmoscope. Results: A total of 2603 subjects participated in the study. 628 subjects (24.1%) were males and 1975(75.8%) were females. The ages ranged from 30 to 91 years (mean=53, median=60 and mode=60). The average CCT in the study population was 528.72±34.40 µm in the right eye and 529.26±35.17 µm in the left eye. The mean IOP for right eye was 13.73±2.89 mm Hg while for the left eye was 13.86±2.86 mm Hg. The mean corrected IOP was 14.71±3.41 mmHg for the right eye and 14.87±3.34 mmHg for the left eye.  Conclusions: Average CCT in the study population was lesser in comparison to the mean CCT among Caucasians resulting in underestimation of the IOP measured by PAT, inducing a Type II error in making the diagnosis of glaucoma with a potential to reduce the sensitivity, increase in false negative rate, and reducing the diagnostic odds ratio for glaucoma.