Abstract
Purpose: :
We have previously reported that the photopic negative response (PhNR) of the focal electoretinograms (ERG; focal PhNR) is correlated with functional loss of the local retina in glaucoma patients (Machida et al., IOVS, 2008). The purpose of this study is to determine the sensitivity and specificity of the focal PhNR to detect glaucomatous eyes with different degrees of visual field defects.
Methods: :
One hundred and fourteen eyes of 114 patients with open angle glaucoma and 42 eyes of 42 normal controls were studied. We classified patients with glaucomatous visual fields into three groups according to Hodapp-Parrish-Anderson criterion (early n=42, intermediate n=51, advanced n=31). The focal ERGs were elicited by a 15° stimulus spot centered on the macula, on the supero-temporal, and on the infero-temporal areas of the macula. The receiver operating characteristic curves were determined to obtain optimal cut-off values. Eyes were classified as being glaucomatous when their focal PhNRs were less than the cut-off values in either retinal area (combined criterion).
Results: :
The focal PhNR amplitudes were significantly reduced with an advance of glaucoma. In early glaucoma, the sensitivities of the PhNR measured for each retinal area ranged from 58.1% to 80.7%. The sensitivities were significantly increased to 90.6% and 96.9% for the focal PhNR amplitude and the focal PhNR/b-wave amplitude ratio, respectively, when the combined criterion was employed. The specificity was >90%. The area under the curve (AUC) ranged from 0.841 to 0.888 and from 0.880 to 0.941 for the focal PhNR amplitude and focal PhNR/b-wave amplitude ratio, respectively. The sensitivity and AUC further increased with an advance of degree of glaucoma.
Conclusions: :
The focal ERG has the diagnostic ability with high sensitivity and specificity in detecting glaucomatous eyes at the early stage, especially when the combined criterion is used. Thus, the focal PhNR can be a good functional parameter to detect early glaucoma.
Keywords: electroretinography: clinical • ganglion cells • electrophysiology: clinical