Influence of the individual characteristics of the patient and the biometric parameters of the eye on the difference between the indicators of point tonometry and tonometry according to Maklakov

Relevance. The main modifiable risk factor for the development and progression of glaucoma is intraocular pressure (IOP). For over two hundred years, there has been a search for a method for determining the level of IOP, which took into account the properties of the surface of the cornea and iatrogenic factors. Purpose. To assess the influence of individual characteristics of the eyeball on the difference in ophthalmotonometry, measured by the Maklakov's applanation method and using point contact tonometry (iCare). Material and methods. The work involved 226 patients aged 45 to 89 years (342 eyes) with a diagnosis of primary openangle glaucoma (POAG) (71 eyes) or suspected glaucoma (202 eyes). The study also used data on the observation of healthy eyes (69 eyes). The study is analytical, observational, case-control. The leading diagnoses at the time of the study were: primary open-angle glaucoma (POAG) and suspected glaucoma. Also, data on observation of healthy eyes were used in the work. Clinical refraction varied of ±6.0 diopters and astigmatism ±3.0 diopters. All patients underwent ophthalmic tonometry measurement using the Maklakov applanation method (with a load of 5, 10 and 15 g) and iCare point contact tonometry (Tiolat, Finland). Results. The results of point contact tonometry were relatively underestimated relative to the tonometric indicators by Maklakov's tonometry: 5 g – 4.1±4.0 (4.0 [1.0; 7.0]), 10 g – 9.7±4.0 (10.0 [6.5; 12.5]), 15 g – 14.7±4.2 (15.0 [12.0; 18.0]). Conclusion. The reasons for the difference from the Maklakov's tonometer require further study; they can be associated both with the measurement method, the patient's body position, the characteristics of the group set, and various approaches to the calibration of the tested tonometers. A positive point is the higher numbers of ophthalmotonus in Maklakov's tonometry, since this is the main screening method of ophthalmotonometry on the territory of the Russian Federation. Keywords: intraocular pressure, elastotometry, rebound tonometry, point contact tonometry, ophthalmotonometry, Maklakov's tonometer