A new study published in the Journal of Cataract & Refractive Surgery established a numerical keratoconus (KC) staging system based on spectral-domain optical coherence tomography (SD-OCT) findings and compared it to existing models.
Talk about the study.
In this retrospective case-control study, investigators performed Scheimpflug tomography, air-puff tonometry, and SD-OCT on 236 normal eyes and 331 eyes with KC.
They assessed SD-OCT-derived parameters of the corneal epithelium and stroma based on:
- Receiver operating characteristic (ROC) curves
- Area under the curve (AUC)
- Sensitivity
- Specificity to discriminate between normal and KC eyes
How was the novel OCT model formulated?
The best-performing parameters were used to develop the SD-OCT-based KC staging system.
Findings?
Researchers found that the highest ranked SD-OCT parameters were:
- Stroma overall minimum thickness ([ST], AUC 0.836, sensitivity 90%, specificity 67%)
- Epithelium overall standard deviation ([EP], AUC 0.835, sensitivity 75%, specificity 78%)
Based on these findings, they developed the STEP (ST + EP) numerical SD-OCT staging system, with five proposed stages.
Tell me more about STEP.
The STEP system demonstrated strong agreement with the two Belin ABCD staging systems—more than 85% of normal patients were in the same stage across all three systems.
Further, for KC patients, agreement between staging systems was still relatively high, ranging from 47% to 77%.
Expert opinion?
According to the study authors, the outcomes “aligned well with previous studies using an alternative SD-OCT device, where the authors demonstrated a good correlation between the degree of visual limitation (and KC severity staging) and stromal and epithelial thickness parameters.”
Limitations?
No patients with progressive KC were included in the study, and this investigation featured only one SD-OCT model.
The authors stated that further research is required to measure the universal applicability of this staging system.
Significance?
This novel KC staging system is the first to factor in epithelial and stromal information, as well as to show a strong agreement with existing staging systems.
Take home.
The authors suggested incorporating this system into clinical practice could potentially improve KC identification, monitoring, and treatment decision-making.