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Sarah MacIver, Marc Sherman, Samantha Slotnick, Jerome Sherman; Comparison Of RNFL Assessment With The Optos P200 and P200Dx. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1034.
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To compare the visibility and clinical utility of the RNFL as imaged with the Optos P200 (P2) and the Optos P200Dx (PDX). The P2 uses a linear polarizer; the PDX uses a circular polarizer.
Images of 50 consecutive patients from both systems OU were reviewed retrospectively. A trained observer evaluated the RNFL (using green separation) on image quality (Q) and RNFL integrity (N).Q was graded on a scale of 1-4: 1: poor overall view of RNFL; 4: well-defined RNFL in at least 1 clock hour. N was graded on a scale of 1-5: 1: profound loss; 5: normal RNFL. N≤3 indicates a probable pathological defect. A clinical diagnosis (Dx) based on DFE and on GDx, OCT and/or VF was used to confirm the presence of a pathological defect.
According to the grading scale, the PDX yielded higher quality RNFL images;. Q≥3 was found in 78 of 100 PDX and in 55 of 100 P2 images. In many P2 images, artifacts obscured the RNFL off the disc, reducing Q. Both systems generally had higher Q in superior RNFL than inferior RNFL. Pathological defects (N≤3) were found in 39 of 100 PDX and 36 of 100 P2 images. Where N≤3, correspondence with Dx was found in 33 (84.6%) PDX and 23 (63%) P2 images.
In this direct comparison study, PDX RNFL images were of higher quality than P2. The circular polarizer in the PDX results in a more uniform quality image translating to greater visibility of the RNFL. The PDX was thus better at accurately detecting pathological RNFL defects than the P2. The image quality produced by the linear polarizer in the P2 limits its ability to detect pathological RNFL defects.
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