Background/aims To propose and validate a new pterygium grading system based on slit-lamp evaluation.

Methods This prospective cross-sectional study included 217 patients with pterygium. All patients underwent slit-lamp examination, and slit-lamp photographs were independently graded by two graders twice. A total of eight parameters were evaluated and all parameters were assigned with a score of 1–4 (normal–severe). Intra-rater and inter-rater reliability as determined by weighted Cohen’s kappa analysis.

Results A total of 868 independent assessment, based on 217 slit-lamp images, were performed by two graders. For conjunctival assessment, the intra-rater reliability was excellent for body thickness (κ=0.81–0.89) and size at limbus (κ=0.87–0.92), substantial-to-excellent for body vascularity (κ=0.72–0.86), and moderate-to-excellent for body length (κ=0.57–0.81), whereas the inter-rater reliability was excellent for size at limbus (κ=0.86), substantial for body thickness (κ=0.72–0.73) and body vascularity (κ=0.66–0.75), and moderate for body length (κ=0.54–0.57). For corneal assessment, the intra-rater reliability was excellent for all four parameters (κ=0.84–0.90) whereas the inter-rater reliability was excellent for head length (κ=0.86–0.87), substantial-to-excellent for head vascularity (κ=0.78–0.82), substantial for Stocker’s line (κ=0.79–0.80) and head thickness (κ=0.67–0.69). The grading system was named SLIT2, which included S tocker’s line, S ize at limbus, L ength of head/body, I njection/vascularity of body/head, and T hickness of body/head.

Conclusion The proposed SLIT2 grading system, consisting of eight components, may serve as a reliable tool to standardise the reporting of pterygium severity and disease recurrence for clinical and research applications.