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A. Ciobanu, A. K. Fansi, P. Harasymowycz; The Validity of Screening for Glaucomatous Optic Nerve Damage Using GDx Variable Cornea Compesation (VCC) Scanning Laser Polarimetry (SLP) With VCC in High Risk Populations. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4643.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate whether scanning laser polarimeter GDx VCC is a valid tool for the detection of glaucomatous optic nerve damage.
This was a prospective, observational, cross-sectional, non-consecutive, population study that took place in Montreal, Quebec, Canada and focused on "high risk" groups for open angle glaucoma development. 240 (480 eyes) subjects were enrolled during a 12 months period. Subjects underwent these tests: FDT, GDx VCC, a standard ophthalmologic examination, including gonioscopy, intraocular pressure, central corneal pachymetry, optic disc grading and fundoscopy.Outcomes measures included positive/negative Likelihood Ratios (LR), sensitivities and specificities, as well as positive/negative predictive values (PPV) of the nerve fiber indicator (NFI) parameter at a cut-off value 30, 35 and 40. Gold-standard definitions of glaucoma (Gold Standart 1- positive vs probable, possible, negative; Gold 2 - positive, probable vs possible, negative; Gold 3 - positive, probable, possible vs negative) varied depending on whether suspects were classified with normals, suspects or glaucoma, based on optic nerve appearance and on FDT results.
Of the original 240 patients examined, 19(8%) were found to have glaucoma. Depending on gold-standard definitions for glaucoma, Specificity ranged from 90% to 98%, Sensitivity from 10% to 100%, PPV from 14% to 65%, NPV from 56% to 100%.In all three test positive groups (NFI>=30,35,40) there was a good correlation between clinical based diagnoses:NFI>=30Gold 1 OS Khi=24, p<0.002; Gold 2 Khi=23, p<0.000, Gold 3 Khi=7, p<0.012Gold 1 OD Khi=27, p<0.001; Gold 2 Khi=14, p<0.005, Gold 3 Khi=3, p<0.072Gold 1 OS or OD Khi=37, p<0.000 Gold 2 Khi=32, p<0.000, Gold 3 Khi=5, p<0.028NFI>=35Gold 1 OS Khi=17, p<0.013 Gold 2 Khi=5, p<0.060, Gold 3 Khi=3, p<0.083Gold 1 OD Khi=33, p<0.001 Gold 2 Khi=18, p<0.003, Gold 3 Khi=4, p<0.037Gold 1 OS or OD Khi=18, p<0.005 Gold 2 Khi=17, p<0.001, Gold 3 Khi=3, p<0.099NFI>=40Gold 1 OS Khi=27, p<0.006 Gold 2 Khi=3, p<0.127, Gold 3 Khi=3, p<0.106Gold 1 OD Khi=19, p<0.011 Gold 2 Khi=5, p<0.084, Gold 3 Khi=2, p<0.143Gold 1 OS or OD Khi=11, p<0.029 Gold 2 Khi=7, p<0.030, Gold 3 Khi=2, p<0.172
This study suggests that a glaucoma screening program may be more effective in detecting POAG when targeting high risk populations. GDxVCC may prove to be a useful tool in detecting glaucomatous optic nerve damage, and could be used as part of a complete glaucoma screening protocol.
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