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Objective To analyze the distribution characteristics of ABCD staging based on the Chinese Keratoconus (CKC) Cohort Study and compare those with the Homburg Keratoconus Center (HKC) in Germany.
Methods A cross-sectional study was conducted, enrolling 1 531 keratoconus patients (2 476 eyes) in the CKC Cohort Study from January 2019 to March 2025 at Henan Eye Hospital. Best-corrected visual acuity was measured using a phoropter, and corneal topography was assessed using the Pentacam HR to determine ABCD staging. The ABCD staging distribution of 1 000 keratoconus patients (1 917 eyes) from the HKC was used as a reference. The differences in gender and age distribution were compared between the CKC group and HKC group. The differences in ABCD staging and the linear trends between the CKC group and the HKC group, as well as between CKC patients aged ≤20 years and >20 years, were compared using the Wilcoxon rank-sum test and a general linear model. This study complied with the Declaration of Helsinki and was approved by the Ethics Committee of the Henan Eye Hospital (No. HNEECKY-2019[5]). All subjects or their guardians were informed of the purpose and significance of the study and signed the informed consent form.
Results There was no significant difference in gender distribution between the CKC and HKC groups ( χ 2=0.312, P=0.577). The mean age of CKC was (22.57±7.05) years, with 723 patients (47.2%) being ≤20 years old, which was significantly higher than 128 patients (12.8%) in the HKC patients ( χ 2=321.183, P<0.001). In the CKC, 797 eyes (32.2%) were classified as A4, the highest proportion in the A stage; 1 288 eyes (52.0%) were categorized as B4, the highest proportion in the B stage; 867 eyes (35.0%) were classified as C1, the highest proportion in the C stage; 1 215 eyes (49.1%) were classified as D1, the highest proportion in the D stage. Compared with the HKC cohort, the CKC cohort exhibited significantly more severe A, B, and C staging ( Z=-5.592, -6.309, -4.467; all P<0.001. F=31.902, 50.801, 12.601; all P linear trend<0.001). The distribution ratios of A, B, and D stages were not statistically significant between the ≤20 years group and the >20 years group ( Z=-0.732, -1.386, -0.526; all P>0.05), and the distribution ratios of C stage between the two age subgroups were statistically significant ( Z=-4.189, P<0.001), with the grade C severity being significantly higher in the ≤20 years group compared with the >20 years group ( F=17.782, P linear trend<0.001).
Conclusions Compared with the HKC patients, patients in the CKC Cohort Study are younger and exhibit more severe ABCD staging. The findings highlight the need to strengthen early screening and treatment as well as clinical management for keratoconus.