There were 30 subjects in the Norm tear group, 26 patients in the IUK group, and 26 patients in the NIUK group (
Table 1). There was no statistically significant difference with respect to sex (χ
2 = χ
2 test with Yates correction;
P = 0.67), age (one-way ANOVA,
P = 0.68), or laterality of the eye (χ
2;
P = 0.85) among the three groups. Comparison of the two groups indicated that contact lens wear and corneal trauma were the most common risk factors for both. Although there was no statistical significant difference for the overall frequencies of these risk factors (χ
2;
P = 0.78), ocular surface diseases were more frequent in the NIUK group and previous UK was more frequent in the IUK group. Because CGMH is a tertiary medical center, several patients had received antimicrobial medication before they participated in this study. However, there was no statistically significant difference for both groups (χ
2;
P = 0.97). Analyzing the morphologic factors for UK indicated a statistically significant difference (χ
2;
P = 0.03) for ulcer boundary pattern because the IUK group had more elliptical ulceration than the NIUK group. There was a tendency for larger ulcer area in the IUK group, but the difference did not reach the statistical significance (one-tailed
t-test;
P = 0.09). There was no statistically significant difference for depth (χ
2;
P = 0.35) or location (χ
2;
P = 0.27). The identified pathogens and risk factors for the IUK group are summarized in
Supplementary Table S1.