Biomechanical properties of human and porcine corneas

The suitability of porcine corneas as approximate models for human corneas in mechanical property characterisation studies is experimentally assessed. Thirty seven human donor corneas and thirty four ex-vivo porcine corneas were tested under inflation conditions to determine their short-term stress-strain behaviour and long-term creep behaviour up to 2.8 h (10,000 s). Vertical strips extracted from further 12 human corneas and 10 porcine corneas were subjected to stress-relaxation tests for up to 20 min at different stress levels. Human and porcine corneas were observed to have almost the same form of behaviour under short and long-term loading. They both exhibited non-linear stress-strain behaviour and reacted to sustained loading in a similar fashion. However, human corneas were significantly stiffer than porcine corneas. They also crept less under long-term loading and could sustain their stress state for longer compared to porcine corneas. These differences, in addition to others identified earlier in relation to corneal mechanical anisotropy, cast doubt on the suitability of porcine corneas as models for human corneas in mechanical studies.