Intraocular pressure is the one modifiable factor, which correct assessment and normalization initiates the treatment of glaucoma. The accuracy of its measurement by traditional methods depends on biomechanical properties of the fibrous tunic of the eye, which in modern clinical practice are most successfully studied by the method of bidirectional applanation of the cornea using the Ocular Response Analyzer (ORA). Mathematical integration of the parameters it measures makes it possible to calculate the coefficient of biomechanical stress (Kbs) that characterizes changes in the fibrous tunic of the eye induced by intraocular pressure, and serves as a criterion for intraocular pressure compensation.
PURPOSE
To determine the range of normal values of the Kbs coefficient, and to evaluate its specificity and sensitivity as a criterion for the degree of intraocular pressure compensation.
MATERIAL AND METHODS
Two consecutive studies on representative clinical material were used to determine the range of normal Kbs values in patients without significant ophthalmic pathologies (400 patients, 800 eyes) and establish the sensitivity and specificity of the coefficient in the diagnosis of glaucoma in patients with newly diagnosed glaucoma (673 patients, 1346 eyes). The age and gender composition of patients in both study groups was similar.
RESULTS
The cut-off value for Kbs is 1.0. In the range of values from 1.0 to 1.09, additional risk factors for glaucoma progression must be taken into account to assess intraocular pressure compensation. In cases when Kbs is equal to or exceeds 1.1, the intraocular pressure is considered elevated and a high risk of disease development or progression is predicted. In glaucoma patients with uncompensated intraocular pressure, the specificity of Kbs is 81.5%, the relative specificity (including the borderline range) is 98%. With Kbs values over 1.1, its specificity reaches 100%.
CONCLUSION
The performed clinical and statistical analysis demonstrates high sensitivity and specificity of the biomechanical stress coefficient in the diagnosis and treatment of glaucoma.
