PURPOSE: To define the clinical characteristics of atypical birefringence imag es and to describe a quantitative method for their identification. DESIGN: Prosp ective, comparative, clinical observational study.METHODS: Normal and glaucomato us eyes underwent complete examination, standard automated perimetry, scanning l aser polarimetry with variable corneal compensation (GDx-VCC), and optical cohe rence tomography (OCT) of the macula, peripapillary retinal nerve fiber layer (R NFL), and optic disk. Eyes were classified into two groups: normal birefringence pattern (NBP) and atypical birefringence pattern (ABP). Clinical, functional, a nd structural characteristics were assessed separately. A multiple logistic regr ession model was used to predict eyes with ABP on the basis of a quantitative sc an score generated by a support vector machine (SVM) with GDx-VCC.RESULTS: Sixt y-five eyes of 65 patients were enrolled. ABP images were observed in 5 of 20 ( 25%) normal eyes and 23 of 45 (51%) glaucomatous eyes. Compared with eyes with NBP, glaucomatous eyes with ABP demonstrated significantly lower SVM scores (P< .0001,< 0.0001, 0.008, 0.03, and 0.03, respectively) and greater temporal, mean , inferior, and nasal RNFL thickness using GDx-VCC; and a weaker correlation wi th OCT generated RNFL thickness (R2=.75 vs. 27). ABP images were significantly c orrelated with older age (R2=.16, P=.001). The SVM score was the only significan t (P< .0001) predictor of ABP images and provided high discriminating power betw een eyes with NBP and ABP (area under the receiver operator characteristic curve =0.98). CONCLUSIONS: ABP images exist in a subset of normal and glaucomatous eye s, are associated with older patient age, and produce an artifactual increase in RNFL thickness using GDx-VCC. The SVM score is highly predictive of ABP images .
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