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Y Sohn, M Banks, J Caprioli, DF Garway-Heath, H Bagga, DS Greenfield; Optimal Measurement Parameters To Distinguish Between Normal And Glaucomatous Eyes Of The Scanning Laser Polarimeter With Fixed And Variable Corneal Compensator Settings . Invest. Ophthalmol. Vis. Sci. 2002;43(13):263. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The variable corneal compensator (VCC) is a modification of the scanning laser polarimeter (SLP) that allows the neutralization of the retardation pattern seen at the macula that is induced by corneal birefringence. The fixed corneal compensator (FCC) allows only the neutralization in eyes with corneal birefringence that matches the population mode. We hypothesised that retinal nerve fiber layer thickness (RNFLT) values would have a greater ability to discriminate between glaucomatous and normal eyes with the VCC setting, compared with the FCC setting. The study aimed to identify the most discriminating parameters with the VCC and FCC settings. Methods: Peripapillary images were taken of 56 eyes of 56 normal subjects (mean age 42, range 19 to 76 years) and 55 glaucomatous eyes of 55 patients (mean age 66, range 30 to 87 years; average mean defect -7.2dB, range 0.26 to -20.33) with the VCC and FCC. Measurements were made around an ellipse 1.75 times the optic disc diameter. Subject ethnic origin was: white 67.6%, black 12.6%, Asian 9.9%, Hispanic 9.9%. There were 69 right eyes,42 left eyes,41 males,70 females. 16 measurement parameters (sector RNFLT, modulation and ratios) were studied. Dependency of parameters on age, gender, ethnic origin and eye side was sought. Parameters that predict glaucoma with p<0.001 in a logistic regression were regarded as good discriminators. Parameters for a discriminant function were generated for the VCC and FCC measurements. The discriminating power of the function was given as the area under the receiver operating characteristic (ROC) curve. Results: Measurement parameters were not related to ethnic origin, gender and eye side. Ellipse average, superior and inferior quadrant RNFLTs were related to subject age with VCC, but not FCC, measurements. Good discriminators for FCC were: superior and inferior modulation parameters (superior or inferior RNFLT minus average nasal and temporal RNFLT). Good discriminators for VCC were: ellipse average, superior and inferior RNFLT and superior and inferior modulation parameters. The areas under the ROC curve were 0.94 (VCC) and 0.86 (FCC). Conclusion: More VCC measurement parameters are able to discriminate between normal and glaucomatous eyes than with the FCC. Absolute RNFLT values obtained with VCC can discriminate well between normal and glaucoma.
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