Combined Scheimpflug-Derived Tomographic and Biomechanical Assessment Detection: A Systematic Review
Purpose: Keratoconus is the most common corneal ectatic disease, characterized by progressive and bilateral thinning of the cornea leading to visual loss. Early diagnosis is important, particularly in preoperative screening, and the utilization of another imaging modality remains crucial. This study aimed to explore the combination of corneal biomechanical tomographic assessment derived from Scheimpflug in diagnosing subclinical keratoconus. Methods: A systematic search was conducted in MEDLINE, Google Scholar, Clinical Key, and EBSCO. Two independent reviewers selected studies and extracted data. Risk of bias was assessed using the QUADAS-2 tool in RevMan 5.4. The primary outcome measures included the Belin-Ambrosio enhanced ectasia total deviation index (BAD-D), Stiffness Parameter at First Applanation (SPA-1), Tomographic & Biomechanical Index (TBI), and Corvis Biomechanical Index (CBI). Diagnostic accuracy was categorized based on the area under the curve (AUC) as low (AUC < 0.7), moderate (0.7 ≤ AUC < 0.9), or high (AUC ≥ 0.9). Results: Twelve studies involving 3483 eyes were included BAD-D and CBI demonstrated low to moderate AUC, while TBI demonstrated moderate to high AUC. According to the QUADAS-2, common methodological limitations included inappropriate reference standards, unclear patient selection, and inconsistent exclusion criteria. Limitations include numerous issues with methodological and findings reporting, thus a meta-analysis was not conducted. Conclusion: Scheimpflug-based corneal tomographic and biomechanical assessment shows promise as an adjunctive tool for detecting subclinical keratoconus. Among the indices, TBI appears to provide the highest diagnostic performance. However, further high-quality, longitudinal studies are required to validate these findings and to develop standardized diagnostic criteria.