Comparison and comparability of pneumotonometry and rebound tonometry results with Maklakov’s applanation tonometry

Abstract

BACKGROUND: Introduction and use of various tonometry methods can lead to misinterpretation of intraocular pressure results and influence the choice of treating approaches by ophthalmologist in a glaucoma patient. AIM: To compare pneumotonometry and rebound tonometry results with Maklakovs applanation tonometry and to develop corrections for their comparability. MATERIALS AND METHODS: The study included 75 patients. All subjects underwent Maklakov applanation tonometry (10 g) and pachymetry (Topcon SP-3000P). In 48 patients (94 eyes) of the 1st group, pneumotonometry (TONOREF II Nidek) was performed, and 27 patients of the 2nd group (52 eyes) underwent rebound tonometry (iCare IC-100). RESULTS: The mean difference in intraocular pressure level in the 1st group was 4.81 (p 0.001), and in the 2nd 0.98 mmHg (p = 0.399). Both methods pneumo- and rebound tonometry showed underestimated results with intraocular pressure less than 23.0 and 22.5 mmHg (respectively) relative to applanation tonometry and, conversely, overestimated intraocular pressure when these values were exceeded. A significant (p 0.001) strong (R2 = 0.86) relationship between applanation and rebound tonometry was obtained, which made it possible, using regression analysis, to develop a formula for recalculating results of iCare tonometry into those of Maklakov tonometry: PMaklakov = 0.40 PiCare + 13.44. CONCLUSIONS: Both pneumo- and rebound tonometry demonstrate adequate results of P0 with intraocular pressure below 23.0 and 22.5 mmHg (respectively) and overestimate the results when these values are exceeded. The developed formula allows converting the results of iCare tonometry into the values of the Maklakovs tonometry.