Detection of Psychophysical and Structural Injury in Eyes With Glaucomatous Optic Neuropathy and Normal Standard Automated Perimetry

Abstract

To compare the prevalence of structural and psychophysical abnormalities in normal eyes and eyes with glaucomatous optic neuropathy (GON) and normal standard automated perimetry (SAP). Complete examination, SAP, short-wavelength automated perimetry (SWAP), frequency doubling technology (FDT), scanning laser polarimetry (GDx-VCC), and optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer (RNFL), optic disc, and macula were performed. Glaucomatous optic neuropathy was defined as cup-disc asymmetry between fellow eyes of greater than 0.2, rim thinning, notching, excavation, or RNFL defect. All eyes had normal SAP. Abnormal measurements on OCT, GDx-VCC, SWAP, and FDT were defined as those outside 95% normal limits. Eyes were stratified into 3 groups based on the OCT-generated vertical cup-disc ratio: mild, moderate, and advanced cupping (cup-disc ratio of <0.4, 0.4-0.7, and >0.7, respectively). Receiver operating characteristic curves were developed to assess sensitivity and specificity of structural and functional assessments. Forty-seven eyes of 47 patients (25 with GON and 22 normal) were enrolled (mean +/- SD age, 58 +/- 16 years; range, 25-83 years). Compared with normal eyes, eyes with GON had significantly worse mean deviation and pattern standard deviation by means of SWAP and FDT (P = .02-.05); OCT-derived mean and superior and inferior RNFL thickness (P = .008, <.001, and .05, respectively); mean macular thickness (P = .01), rim volume, rim area, cup-disc ratio, and cup area (all P<.001); and GDx-VCC nerve fiber indicator and inferior average (P = .03). There was a significantly (P = .008, .002, .003, and .01, respectively) greater prevalence of abnormalities identified by SWAP, FDT, OCT and GDx-VCC in eyes with advanced cupping (43%, 43%, 57%, and 57%, respectively) compared with mild cupping (0%) and moderate cupping (9%, 5%, 19%, and 33%, respectively). Eyes with GON and normal results of SAP have significantly greater structural and psychophysical abnormalities than do normal eyes evaluated by means of OCT, GDx-VCC, SWAP, and FDT. Eyes with increased vertical cup-disc ratio are more likely to manifest such abnormalities on advanced diagnostic testing.