A comparison of postural and diurnal variatons in intraocular pressure using the iCare rebound tonometer and Perkins applanaton tonometer in admited adults in Kenya

Abstract

Background: Elevated intraocular pressure (IOP) remained the most important known risk factor for glaucoma. Aim: To compare the postural and diurnal IOP variations using the iCare rebound tonometer (RT) and Perkins applanation tonometer (PAT). Setting: Kakamega County Hospital, Kenya. Methods: Elevated intraocular pressure measurements were taken by two (masked) examiners with two devices in the morning (06:00-09:00), midday (12:00-15:00) and evening (18:00-21:00), in the sitting followed by supine positions in one randomly selected eye of 24 oculo-visual healthy hospital-admitted patients. Effects of the time of the day and position of the body within and between devices were analysed with the Statistical Package for Social Sciences. Results: The mean IOP measured by the RT ranged from 6 mmHg to 24 millimetres of mercury (mmHg) in the sitting position and from 10 mmHg to 26 mmHg in the supine position. The mean IOP measured using PAT ranged from 6 mmHg to 21 mmHg in the sitting position and from 8 mmHg to 24 mmHg in the supine position. The IOP measured by both devices significantly varied with position (p < 0.05). Perkins applanation tonometer on average gave a significantly higher IOP (1.7 mmHg [p = 0.003] and 1.3 mmHg [p = 0.034]) at 06:00 compared to that at 12:00 and 18:00, respectively. The IOP readings with the RT were on average 2.2 mmHg and 3.0 mmHg higher at 06:00 compared to that at 12:00 and 18:00, respectively (p < 0.0005). Conclusion: Significant reductions were observed in postural and diurnal IOPs in the sitting positions and in the afternoon, respectively. Diurnal IOP variations were slightly higher when measured by RT compared to when measured by PAT.