Refractive Surgery, Ocular Rigidity and Goldmann Tonometry

Abstract

Abstract: : Purpose: To investigate the effect of local corneal thickness and stiffness changes on ocular rigidity and Goldmann Applanation Tonometry (GAT) measurements. Methods: 20 fresh enucleated porcine eyes underwent Laser in Situ Keratomileusis (10 Diopters phototherapeutic keratectomy at 7mm optical zone) and ocular rigidity was measured by means of a computerized microdocimertric device capable to continuously monitor IOP. The ocular rigidity of another 20 intact eyes was measured to serve as control. In a third group of 20 fresh enucleated porcine eyes GAT was measured before and after a partial trephination at half corneal thickness (580um) while the pressure was hydrostatically controlled at 40 mmHg; ocular rigidity was also measured in this group before and after partial trephination. Results: Eyes which underwent LASIK had a mean value of ocular rigidity 0.0257±0.0041mmHg/µl, while the control group had a mean value of 0.0222±0.0047mmHg/µl. The difference between the two samples was statistically insignificant (p<0.0364). GAT measurements in eyes before and after cornel trephination had mean values of 30±6mmHg and 19±4mmHg respectively (p<0.0001). Measurement of ocular rigidity was not affected by trephination. Mean values of ocular rigidity were 0.0160±0.0023mmHg/µl and 0.0174±0.0035mmHg/µl before and after trephinations respectively which were of no statistically significant difference (p<0.156) Conclusions: Ocular rigidity did not seem to be affected neither by the reduction of corneal thickness, induced by refractive surgery, nor by partial thickness trephination. However, partial thickness trephination did significantly changed the GAT measurement and we speculate that this is caused due to the local corneal stiffness changes.

Keywords: cornea: stroma and keratocytes • cornea: stroma and keratocytes • cornea: stroma and keratocytes