Mathematical projection model of visual loss due to fuchs corneal dystrophy

Purpose. To devise a mathematical disease classification model for eyes with primary guttata cornea, on the bases of endothelial loss trajectory and probability of advanced disease. Methods. A series of 1971 patients (3281 eyes), some with and some without guttata corneas, undergoing specular microscopy were retrospectively reviewed. The eyes were classified into four stages; stage 0, without guttae; 1, guttata cornea without edema; 2, mild Fuchs' corneal dystrophy (FCD); and 3, severe FCD, according to clinical records, and patient age and corneal endothelial cell density (ECD) were plotted. Nonparametric density smoothing was used to create a contour map, and a best-fit curve for ECD loss was calculated. The relation between ECD decrease rate and the stages were evaluated. Results. Endothelial decrease rate in stage 0 was 0.44%/year, which was compatible with that of normal eyes reported in previous studies. Decrease rates of stages 1, 2, and 3 were 0.81%, 2.65%, and 3.08%/ year, respectively. The age-ECD loss curves of 1.40%/year (ECO _1.4) and 2.00%/year (ECO _2.0) further divided stage 1 into three subgroups; stage 1a, asymptomatic guttata cornea; 1b, borderline guttata cornea; and 1c, pre-FCD. The ECO _2.0 cutoff line differentiated eyes with FCD from those without edema with a sensitivity and specificity of >90%. Stage 1c eyes were below ECO _2.0 and had a decrease rate as high as FCD. Conclusions. This mathematical model can be used to predict the prognosis of patients with primary guttata cornea.