Abstract
Purpose: :
To determine whether a significant relationship exists between the photopic negative response (PhNR) of the focal electoretinogram (ERG) and the local structures of the inner retina and optic nerve head in glaucoma.
Methods: :
Sixty-one eyes of 61 patients with open angle glaucoma (OAG), 13 eyes of 13 glaucoma suspects, and 30 eyes of 30 normal subjects were studied. The focal ERGs were elicited by a 15° circular white stimulus on a white background centered on the macula (center). The focal ERGs were also elicited by half of an annulus placed above or below the macula (superior and inferior half annuli). The diameter of the inner border of the annulus was 15° and that of the outer border was 30°. The structure of the optic nerve head and retinal nerve fiber layer thickness (RNFLT) were evaluated by HRTII and GDx, respectively. These structural parameters were analyzed for the superior/temporal (0-45°), temporal (45-135°), and inferior/temporal (135-180°) sectors which are assumed to consist mainly of neurons from the retinal areas corresponding to the superior half annulus, the center, and the inferior half annulus, respectively.
Results: :
The amplitude of focal PhNR and ratio of focal PhNR/b-wave amplitude decreased significantly with a thinning of the RNFLT in the superior/temporal and inferior/temporal retinal areas (r = 0.43 to 0.47; P <0.0001), although the temporal area was not significant. The focal PhNR amplitude and focal PhNR/b-wave amplitude ratio were also significantly correlated with the corresponding rim areas (r = 0.38 to 0.50, P <0.0001) and cup/disc area ratio (r = -0.43 to -0.49, P <0.0001).
Conclusions: :
These results suggest that the anatomical losses of retinal neurons in local areas of the retina or optic nerve head are a cause of the reduction in the amplitude of the focal PhNR in OAG.
Keywords: electroretinography: clinical • ganglion cells