AIM: To explore the diagnostic value of visualized corneal biomechanical analysis combined with Pentacam related-index in the diagnosis of subclinical keratoconus and forme fruste keratoconus, and to provide evidence for early screening and diagnosis of keratoconus.

METHODS: A total of 65 patients(128 eyes)with keratoconus in Ningxia Eye Hospital from November 2018 to November 2019 were enrolled in a diagnostic trial design. According to the course of disease, these eyes were divided into clinical, subclinical and forme fruste groups. A total of 89 subjects(89 eyes)who received preoperative refractive examination at the same period were selected as the normal control group. Pentacam combined with Corvis ST was used for detection. Corneal dilatation indexes, including belin/ambrosio enhanced ectasia display(BAD-D), the thinnest point thickness(TP), max keratometry(Kmax), deviation of normality of the front elevation(Df), deviation of normality of the back elevation(Db), deviation of normality of pachymetric progression(Dp), deviation of normality of corneal thinnest point(Dt), deviation of normality of relational thickness(Da), and Ambrósio relational thickness horizontal(ARTh), corneal biomechanical indexes, including Corvis biomechanical index(CBI), deformation amplitude ratio(DA Ratio), stiffness parameters at applanation 1(SP-A1)and Integrated radius, biomechanical intraocular pressure(bIOP)and tomographic and biomechanical index(TBI)were recorded. The keratoconus at different stages was statistically analyzed, the diagnostic valve of TBI, CBI and BAD-D was explored by receiver operating curve, and the diagnostic value of each parameters was evaluated.

RESULTS:The TBI, BAD-D, TP, Kmax, Df, Db, Dp, Dt, Da, ARTh, CBI and SP-A1 of the clinical keratoconus group had strong diagnostic ability, the BAD-D, Da, Dp, TP, TBI, CBI, ARTh and Integrated radius of the subclinical keratoconus group had strong diagnostic ability, and the BAD-D, Dp and TBI of the forme fruste keratoconus group had certain diagnostic and predictive ability.

CONCLUSION:TBI, BAD-D, Dp and other index have a certain sensitivity and specificity for early keratoconus diagnosis, and can be used for screening and early diagnosis of keratoconus.