Corneal tomographic and biomechanical factors associated with keratoconus progression
Purpose: To determine corneal biomechanical and tomographical factors associated with keratoconus progression.
Methods: Data of 84 keratoconus patients who had at least 1 year of follow-up with at least 3 concurrently performed separate examinations of Ocular response analyzer (ORA) and Pentacam were included in this study. Tomographically better eye was chosen as the study eye. Progression was defined as the presence of progressive change in two consecutive visits for any single parameter ?95% CI or two parameters ?80% CI for the normal population as assessed by the Belin ABCD Keratoconus progression display. Analyzed Pentacam parameters were Kmax, minimum pachymetry, apex pachymetry and Belin Ambrosio Enhanced Ectasia Display Final D value. Corneal hysteresis (CH) and corneal resistance factor (CRF) along with the waveform parameters from ORA were analyzed. Factors associated with keratoconus progression were evaluated using t-tests and stepwise logistic regression.
Results: There were 44 (mean age: 29.3± years, female: 26) and 40 (mean age: 30.2± years, female: 19) patients in the progressive and non-progressive groups, respectively. Although Pentacam parameters along with CH and CRF were similar between the two groups, ORA waveform parameters derived from the second applanation signal (uslope2, slew2, aspect2, mslew2, dive2, h2) were statistically significantly higher in the non-progressing group (all p< 0.05). A 10 unit increase in uslope2 reduced the likelihood of keratoconus progression by approximately 30% in the logistic regression analysis (ß= 0.707, p=0.001, model r2=0.27).
Conclusions: Parameters derived from the second applanation signal of ORA may be predictive of keratoconus progression.