The impact of central corneal thickness on intraocular pressure measurement using Perkins applanation, iCare rebound, and Pulsair non-contact tonometers

Objecives: This study aims to compare the impact of central corneal thickness (CCT) on intraocular pressure (IOP) measurements using a non-contact tonometer (NCT), Pulsair, iCare rebound tonometer (RBT), and Perkins applanation tonometer (PAT) in adult patients at the Eye Clinic of University of Port Harcourt Teaching Hospital, Rivers State, Nigeria. Material and Methods: This was a comparative cross-sectional study of 92 (184 eyes) adults aged 18 and older. Their sociodemographic data were collected and an ocular examination was performed. Intraocular pressure measurements were done first using the NCT, then RBT, and finally PAT. An average of two readings was taken for all the devices, and there was a 10-minute interval between measurements. CCT was then assessed. Results: Using PAT, the mean pachymetrically corrected IOP by perkins applanation tonometer (cPAT) in the right eye (RE) was 15.48 ± 4.17 mmHg, and in the left eye (LE), cPAT was 14.16 ± 3.53 mmHg. Using NCT, pachymetrically corrected IOP with non-contact tonometer (cNCT) measured was 15.48 ± 3.55 mmHg (RE) and 15.55 ± 3.41 mmHg (LE). With RBT, pachymetrically corrected IOP using rebound tonometer (cRBT) was 16.54 ± 4.51 mmHg (RE) and 16.75 ± 4.09 mmHg (LE). There was a weak, statistically significant inverse correlation between pachymetrically corrected IOP and CCT for all instruments except with RBT in the RE. PAT was found to be the most affected by CCT following pachymetric correction, while RBT was the least affected. Conclusion: The PAT was most affected by the CCT, while the iCare RBT was least affected. It is necessary to have measured IOP corrected for CCT to get the true IOP.