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N.S. Levy, B.B. Barnes, R.A. Schachar; GDxVCC for Assessment of Retinal Pathology . Invest. Ophthalmol. Vis. Sci. 2005;46(13):268.
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Purpose: To evaluate a method developed for determining the polarization retardance at any site on the retina and utilize this reference value as a basis for identifying retinal pathology. Methods: GDxVCC is an instrument employed for measuring the polarization retardance from the peripapillary ganglion cell axons. The amount of polarization has been related to the axon density. GDxVCC records, previously obtained from10 glaucoma suspect eyes, were reevaluated. These eyes had no retinal nerve fiber nor visual field abnormality. The polarization retardance is customarily determined from a ring shaped area of 64 cells that surround the optic nerve head. These equally sized cells are eight pixels in width and 5.6 degrees in circumference. We moved this data acquisition ring to an area of the retina distant from the optic nerve and determined the polarization in each cell at this new location. Each cell provided a measure of polarization retardation from its underlying normal retina. The ring was then shifted five pixels from this baseline position in each of the 8 cardinal directions. The retardance from each of the shifted cells was recorded. The average retardance from the eight cells surrounding each baseline cell was calculated and compared to that of its reference. Results: Bland Altman analysis demonstrated that the average polarization retardance of the surrounding cells correlates closely with that of that of its reference. Using this methodology, pathologic retinal lesions were examined for a change in polarization retardance. Conclusions: GDx scanning laser polarimetry can be utilized to assess the effect of retinal pathology on retardance.
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