Interventions:
The authors justified their selection of the comparators. Penetrating keratoplasty was commonly used for corneal transplantation worldwide, while DALK was the new approach, which was gaining popularity because of its advantages over penetrating keratoplasty. No intervention was included as a comparator.
Effectiveness/benefits:
Selected sources were used for the clinical inputs. Most of the evidence came from the review of patients’ charts at one institution in the authors’ setting. There were some differences between patients in the DALK and penetrating keratoplasty groups at baseline, which might have biased the results. A more robust source of evidence would have been better for assessing the clinical differences between the two procedures, but some of the critical assumptions were tested in the sensitivity analyses. Little evidence was found for the long-term graft failure rates, and conservative assumptions were made and were generally robust to variations. QALYs were a valid and appropriate benefit measure as keratoconus has a big impact on health-related quality of life. Published algorithms were used to convert visual acuity to utility values and these are likely to have been validated.
Costs:
The cost categories were consistent with the perspective adopted. The unit costs, most of the resource quantities, and the data sources were clearly reported, enhancing the transparency of the study. The authors stated that the costs were incurred within the first year after surgery, so no discounting was applied. Reflation exercises in other time periods might be difficult as the price year was not reported. The costs were treated deterministically, but alternative cost estimates were assessed in the sensitivity analyses.
Analysis and results:
The expected costs and benefits were clearly presented and were combined using an appropriate incremental approach. The results appear to have been robust, but the uncertainty was investigated for selected inputs only and no probabilistic analysis was conducted. The authors compared their findings with those from another published study, carried out in the USA, which had similar results. It was acknowledged that the main limitation of the analysis was the lack of good long-term clinical evidence. The results appear to be specific to the authors’ context. The authors stated that their results were applicable only to patients with bilateral corneal disease.
Concluding remarks:
The methods were valid and transparent, which makes the authors’ conclusions robust, but there were some weaknesses in the designs of the main clinical sources.