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Abstract #75502 Published in IGR 19-2
Effect of the Age-Related Corneal Elasticity on Applanation Tonometry
Sperlich K; Reiß S; Bohn S; Stolz H; Guthoff RF; Jünemann A; Stachs OKlinische Monatsblätter für Augenheilkunde 2017; 234: 1472-1476
Elevated intraocular pressure (IOP) is accepted to be one important criterion for glaucoma and is usually measured by applanation or rebound tonometry. The individual uncertainty due to central cornea thickness (CCT) is thereby corrected, while the error induced by age-related elastic modulus (EM) change of the cornea is ignored. To investigate its influence on IOP measurement, we derive a model including also the elastic modulus. Our approach is based on known equations from experimental physics and several assumptions being justified in this paper. Our correction values are in good agreement with the Dresden correction table for low CCT values up to 650 µm using a mean EM of 0.29 MPa. An EM variation from 0.2 to 0.5 MPa, which relates to ages from infancy to 90 years, results in an IOP error of up to 10 mmHg. A variation of the cornea curvature from 7.4 mm to 8.0 mm results in a total IOP change of about 3 mmHg, which is usually neglected. The derived model shows that established correction formulas can be insufficient for a reliable IOP determination. In many cases, the conventionally measured IOP may be precise enough, but the uncertainty in IOP determination due to CCT and EM influence are almost in the same range. Measuring the IOP using applanation methods with established correction formulas should not be overestimated without to respect the EM of the cornea.
Augenklinik, Universitätsmedizin Rostock, Rostock.
Full articleClassification:
6.1.1 Devices, techniques (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
6.1.3 Factors affecting IOP (Part of: 6 Clinical examination methods > 6.1 Intraocular pressure measurement; factors affecting IOP)
2.2 Cornea (Part of: 2 Anatomical structures in glaucoma)