Biomechanical and morphological changes of rabbit corneas under collagenase type II and negative pressure: three months follow-up observation

Abstract

<jats:title>Abstract</jats:title> <jats:p>Background To investigate biomechanical and morphological changes of rabbit cornea ectasia induced by collagenase type II and negative pressure during 3 months after treatment. Method Eighteen New Zealand white rabbits were randomly and evenly arranged into three groups. The left corneas were continuously treated by negative pressure suction (NP group) with 500 mmHg for 30 min once two days, three times in total. The central area of left corneas were soaked in the collagenase type II (CII group) solution (200 μL of 3 mg/ml) for 30 min. The left corneas (CP group) were disposed as CII group firstly, then applied negative pressure suction as NP group for once after 5 days. All right corneas were treated as control eyes. Corneal morphology parameters and Ocular Response Analyzer (ORA) output parameters were collected in vivo once a week for three weeks after treatment and before execution. Histology and biomechanics were tested in vitro at the third month after treatment. Paired t-test and repeated measures analysis were used to determine if there were differences in biomechanical and morphological related parameters across time. Results In NP group, corneal thickness and diopter changed to some extent after treatment immediately, and the elastic modulus increased and relaxation degree slowed after 3 months. In CII group, corneal diopter increased, corneal central thickness (CCT) and corneal hysteresis (CH) decreased at the second week after treatment, which showed the characters of ectatic corneas. Then the degree of ectasia decreased with time. No regular changes was found on experimental corneas in CP group. Conclusions Collagenase type II results in ectatic corneas around two weeks after treatment, but the degree of ectasia decreased with time, and there was no significant difference compared with the controls after 3 months. After negative pressure suction, corneal morphology changed in a short period, and elastic modulus increased and relaxation time increased after a three months recovery, indicating that the negative pressure suction do have a certain effect on corneas.</jats:p>