Abstract
To compare grayscale-derived visible surface characteristics and Pseudomonas aeruginosa adhesion between unworn orthokeratology lenses and lenses worn for approximately 12 months, and to explore associations between grayscale-derived parameters and bacterial adhesion. Sixty orthokeratology lenses were analyzed, including 20 unworn lenses and 40 lenses worn for approximately 12 months. Each worn lens was collected from a different wearer during routine replacement. Standardized slit-lamp images were analyzed with ImageJ to obtain mean gray value and gray-level standard deviation within the central 6.0-mm optical zone. In vitro P. aeruginosa adhesion was quantified as log10-transformed colony-forming units. Group differences were assessed using two-way ANOVA followed by exploratory simple-effect comparisons with Holm adjustment, and correlations between grayscale-derived parameters and bacterial adhesion were explored among worn lenses. Clinical wear was associated with significantly higher mean gray value, gray-level standard deviation, and P. aeruginosa adhesion compared with unworn lenses (all P < 0.001). Exploratory simple-effect comparisons identified higher mean gray value and bacterial adhesion in worn type A than worn type Z lenses after Holm correction, whereas the gray-level standard deviation difference did not remain significant after correction. None of the wear × lens-system interaction terms in the primary ANOVA was statistically significant. Grayscale-derived parameters were only weakly correlated with bacterial adhesion, and these associations were not significant after correction for multiple testing. Orthokeratology lenses worn for approximately 12 months showed greater grayscale-derived visible surface alteration and higher P. aeruginosa adhesion than unworn lenses. These laboratory findings do not establish an increased clinical infection risk or an optimal replacement interval and require prospective clinical validation.