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First Author: S.Venkatarathinam INDIA
Co Author(s): D. Gadre M. Balakrishnamoorthy
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To evaluate if the Intraocular pressure (IOP) measured by a Goldman Applanation Tonometer (GAT) and that measured by TOPCON CT-80 Non Contact Tonometer (NCT) are significantly different even when measured by the same person & to study the effect of central corneal thickness (CCT) on the IOP as measured by NCT and GAT.
Prospective study in a tertiary eye care centre in South India.
IOP and CCT were measured for 200 eyes of 100 patients who walked into the out-patient department (OPD) of a tertiary eye care centre in South India. The IOP was measured using a GAT and a NCT. The CCT was measured using the ultrasonic pachymetry by Sonomed ultrasonic machine. All the measurements were taken by a single observer in a random order. The difference in IOP values obtained via the two methods and the influence of CCT values on the same were analysed.
The eyes were divided into 3 groups, on the basis of the GAT & CCT values obtained. Based on GAT values, the groups were patients with IOP <15 mm Hg; 15-20 mm Hg and >20 mm Hg & those based on the CCT were CCT <500 microns; 500-550 microns; >550 microns. The results were analysed as a whole as well as for each group individually. The mean IOP by the GAT method was 15.63(+/-4.17) mm of Hg and that measured through NCT was 16.51(+/-5.02) mm of Hg. The mean difference between the IOP measured via the two methods (NCT-GAT) was -0.91(+/-2.84) mm of Hg. The mean CCT was 525.47(+/- 35.39) microns.
With higher IOP (>20mm Hg) - the difference between the NCT & GAT values is significant. While in patients with IOP <20 mm Hg, the difference between NCT & GAT is not significant. For IOP values of <20 mmHg in patients with corneal thickness >500 microns, NCT & GAT are comparable. Hence we conclude that in a high volume practice, NCT if combined with CCT can be used for IOP follow up in appropriate candidates.