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P.J. Lama, S. Walsman, A.S. Khouri, R. Thaker, R.D. Fechtner; Atypical GDx/VCC Scans: Quantitative versus Qualitative Assessment and Correction with GDx/ECC . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3643.
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© ARVO (1962-2015); The Authors (2016-present)
To compare an objective scan score versus a subjective clinical grading method in assessment of the degree of atypical birefringence obtained following scanning laser polarimetry (SLP) with the GDx/VCC analyzer in African–American eyes. To assess the utility of GDx/ECC in correcting for the abnormal birefringence signals.
Retrospective consecutive case series of African–American glaucoma patients and suspects who underwent SLP with the GDx/VCC with or without investigational software, GDx/ECC. Qualitative assessment of GDx/VCC scans were graded by a glaucoma specialist and classified into 3 categories based on the presence and extent of abnormal birefringence as completely typical, possibly atypical, and likely atypical. Quantitative typical scan scores were obtained from exported raw image data for each individual patient. Quantitative typical scan scores were then compared with qualitative scan scores in terms of agreement or disparity. GDx/ECC was then performed to evaluate its effect on reducing the atypical birefringence signals both qualitatively as well as its absolute effect on typical scan scores.
A total of 76 eyes of 39 patients were successfully imaged and analyzed. A total of 40 scans were subjectively graded as completely typical, 19 were possibly atypical, and 17 were likely atypical. Quantitative typical number scores ranged from 0–100 (0 was completely atypical and 100 was completely typical). The scanned eyes classified subjectively as completely typical, possibly atypical, and likely atypical had mean quantitative scores of 97.8, 83.0, and 53.9 respectively. GDx/ECC was highly successful in correcting the abnormal birefringence signals. A total of 16/18 scanned eyes had a significant correction both qualitatively and quantitatively with the GDx/ECC software upgrade, with 13/16 corrected to a typical score of 100.
Abnormal birefringence signals can be judged both qualitatively and quantitatively with fairly good correlation. Although there were many scanned eyes with a variable degree of "atypicality" or abnormal birefringent signals, clinical diagnostic discriminatory ability in many such instances was not impaired. The GDx/ECC software strategy is designed to increase the signal to noise ratio thereby improving both scan quality and in some cases diagnostic discriminatory ability.
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