A Clinical Decision Tree to Support Keratoconus Patients Considering Corneal Cross-Linking Combined with Refractive Treatment.

Background: To develop a fast and frugal decision tree to identify keratoconus patients most likely to benefit visually from the combination of corneal cross-linking (CXL) with topography-guided photorefractive keratectomy ("CXL plus").

Patients And Methods: The outcome of interest was an improvement in uncorrected distance visual acuity (UDVA) by at least two lines at the 12-month follow-up. Preoperative and 12-month follow-up data from patients who received CXL plus (n = 96) and CXL only (n = 96) were used in a recursive partitioning approach to construct a frugal tree with three variables (corneal thickness [>/< 430 um], patient interest in CXL plus [yes/no], and tomographic cylinder [ 3 D]). In addition, we estimated the probability of the outcome from a multivariate logistic regression model for each combination of variables used in the decision tree.

Results: In the complete sample, 101/192 (52.6%) patients improved by at least two lines at the 12-month follow-up. Patients affirmative in all three answers had a 75.6% (34/45) probability of gaining at least two lines of improvement in UDVA by CXL plus. The statistical model estimated a 66.0% probability for a successful outcome.

Conclusion: A fast and frugal tree consisting of three variables can be used to select a patient group with a high likelihood to benefit from CXL plus. The tree is useful in the preoperative counseling of keratoconus patients contemplating the CXL plus option, an intervention that is not fully covered by many health insurances.