The full-field flicker test in glaucomas: influence of intraocular pressure and pattern of visual field losses

Abstract

Background: The purpose of this study was to evaluate how temporal contrast sensitivity (TCS) determined with full-field flicker stimuli is influenced by intraocular pressure and whether TCS is reduced in glaucoma patients with diffuse perimetric losses as well as in patients with localized visual field deficits.

Methods: TCS was determined with sinusoidally flickering light (37.1 Hz) in a full-field bowl. Perimetric mean defect (MD) and cumulative defect curves (Octopus G1) were used to distinguish between patients with localized and diffuse field deficits. Normal subjects (296), low-tension glaucoma patients (98) and open-angle glaucoma patients with previously elevated intraocular pressure (541) were classified into five subgroups taking into account the depth of their visual field losses.

Results: No significant correlation between full-field flicker sensitivity and prevailing intraocular pressure was found in normals (Y=1.36+0.006 X) or in patients (Y=0.95-0.0002 X). Analyses of validity at a predefined specificity of 90% reveal a reduction of TCS in patients with early (MD<5 dB) diffuse perimetric losses (sensitivity 69%) as well as in those showing localized visual field defects (sensitivity 65%). Sensitivity was 87% in patients with diffuse perimetric defects (MD 5-10 dB), 93% in a group of patients with both types of losses, and 100% in advanced glaucomas (MD>20 dB). The lack of TCS is similar in open-angle glaucomas and in field-loss-matched normal-tension glaucoma patients.

Conclusions: Significantly reduced TCS in patients with early diffuse perimetric losses as well as in those showing localized visual field defects indicates that localized damages can be associated with general deterioration of the ability to perceive flickering stimuli. Thus, this flicker test can be performed in a full-field bowl with no need for fixation. Considering its other clinical qualities (photopic conditions, low influence of prevailing intraocular pressure and media opacity) the test may be a useful, convenient supplementary procedure in glaucoma screening.