To investigate biomechanical and morphological changes of rabbit cornea ectasia induced by collagenase type II and negative pressure during 3 months after treatment.
Eighteen New Zealand white rabbits were randomly and evenly arranged into three groups. In group NP, the corneas were continuously attracted by negative pressure with 500 mmHg for 30 min, treated by every other day, three times in total. In group CII, the corneal central zone was soaked in the collagenase type II solution (200 μL of 3 mg/ml) for 30 min. In group CP, the corneas were disposed as group CII firstly, then applied negative pressure as group NP for once after 5 days. All right eyes were treated as control eyes. Corneal morphology and biomechanical related parameters were observed 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.
Corneal diopter and corneal central thickness (CCT) changed to some extent after treatment immediately as a result of negative pressure in group NP. The corneas in Group NP had smaller elastic modulus and slower relaxation degree compared with the control one 3 months after treatment. In Group CII, corneal diopter increased, CCT and CH decreased at the second week after treatment, which showed the characters of ectatic corneas. At the third month after treatment, elastic modulus (EL) of the experimental eyes decreased slightly compared with the control eyes. Due to the large individual differences, there were no regular changes on experimental corneas in Group CP.
Cornea socked with collagenase type II showed the obvious characteristics of ectatic cornea at the second week after treatment, but the characteristics disappeared gradually. Negative pressure can result in the change of corneal thickness and diopter in a short period of time, and the degree of swelling and duration are far less than Group CII, but the changes of biomechanical parameters are more obviously than Group CII.