Comparative study of corneal tangent elastic modulus measurement using corneal indentation device

The aim of this study is to examine the corneal tangent modulus measurement repeatability and performance of the corneal indentation device (CID). Twenty enucleated porcine eyes were measured and the eyes were pressurized using saline solution-filled manometer to 15 and 30 mmHg. Corneal tangent moduli measured using the CID were compared with those measured using high precision universal testing machine (UTM). The within-subject standard deviation (Sw), repeatability (2.77×Sw), coefficient of variation (CV) (Sw/overall mean), and intraclass correlation coefficient (ICC) were determined. The mean corneal tangent moduli measured using UTM and CID were 0.094±0.030 and 0.094±0.028 MPa at 15 mmHg, and 0.207±0.056 and 0.207±0.055 MPa at 30 mmHg, respectively, with a difference less than 0.13%. The 95% limit of agreement was between -0.009 and 0.009 MPa. The Sw, repeatability, CV and ICC of corneal tangent moduli measured by the CID were 0.006 MPa, 0.015 MPa, 4.3% and 0.993, respectively. The results showed that the corneal tangent moduli measured by the CID are repeatable and are in good agreement with the results measured by the high precision UTM.