AIM: To investigate and analyze the changes of corneal biomechanics of normal eyes, forme frusta keratoconus eyes, subclinical keratoconus eyes and clinical keratoconus eyes by Corneal visualization Scheimpflug technology(Corvis ST), and provide clinical basis for early diagnosis of keratoconus.

METHODS: Case-control study. We randomly selected 40 normal eyes as normal group, 15 forme frusta keratoconus eyes as forme frusta keratoconus group, 23 subclinical keratoconus eyes as subclinical keratoconus group, and 40 clinical keratoconus eyes as keratoconus group. The biomechanical parameters of each group were measured by Corvis ST. The receiver operating characteristic(ROC)curves was plotted to distinguish keratoconus from the normal cornea.

RESULTS: There was no significant difference in the parameters of biomechanics between normal group and forme frusta keratoconus group (P>0.05). Compared to normal group and subclinical keratoconus group, the parameters second applanation length(AL2), first velocity of applanation(AV1), central curvature radius at highest concavity(HC-radius), deformation amplitude(DA)were revealed statistically significant differences(P<0.05). The biomechanical parameters of the keratoconic group were significantly different from those of normal group except for the second velocity of applanation(AV2), time from the start until the highest concavity(HC-time), peak distance(PD). ROC curve showed that the DA(area under the curve:0.891±0.028)was the best predictive parameter to distinguish keratoconus from the normal eyes.

CONCLUSION: The corneal biomechanical parameters of forme frusta keratoconus group are not changed compared with normal group. The changes between normal group and subclinical keratoconus group should combine with other technology to further improve subclinical keratoconic screening. Compared with normal corneas, keratoconus has a great change in biomechanics, which DA diagnosis of the highest efficiency.