Get access

Comparison of biomechanical parameters in penetrating keratoplasty and normal eyes using the Ocular Response Analyser


Professor Sunil Shah, Heart of England Foundation Trust, Lode Lane, Solihull, West Midlands B91 2JL, UK. Email:


Background:  To compare corneal hysteresis (CH) and corneal resistance factor (CRF) in eyes 1 year following penetrating keratoplasty (PK) with that of normal eyes using the Ocular Response Analyser.

Methods:  Prospective case comparison of 166 normal right eyes and 34 unilateral post-PK eyes presenting to a teaching hospital in Birmingham, UK. The CH, CRF and Goldmann-correlated intraocular pressure, of each eye was measured using the Ocular Response Analyser. The central corneal thickness (CCT) was measured using an ultrasonic pachymeter.

Results:  The mean CH was 10.6 ±2.0 mmHg, standard deviation (SD) and CRF was 10.2 ± 2.0 mmHg (SD) in normal eyes and 8.9 ± 3.3 mmHg and 8.1 ± 3.3 mmHg in post-PK eyes, respectively. The mean CCT was 541.8 ± 36.1 µm in normal eyes and 556.0 ±69.2 µm in post-PK eyes. The Goldmann-correlated intraocular pressure was 16.1 ± 3.1 mmHg and 12.4 ± 2.9 mmHg in normal eyes and post-PK eyes, respectively. The CCT was found to be higher in post-PK eyes compared with normal eyes but the difference was not statistically significant (P > 0.5).

Conclusion:  Reduced biomechanical measures were found in post-PK eyes despite a higher mean CCT. This may be due to the altered corneal structure following PK.

Get access to the full text of this article