Correlation between photopic negative response of focal electroretinograms and local loss of retinal neurons in glaucoma.
OBJECTIVE
To determine the relationship between the photopic negative response of the focal electroretinogram and the structural parameters of the inner retina and optic nerve head in glaucoma.


METHODS
Sixty-one eyes of 61 patients with open angle glaucoma, 13 eyes of 13 patients who were classified as glaucoma suspects, and 30 eyes of 30 normal subjects were studied. The focal electroretinograms were elicited by a 15 degrees circular white stimulus on a white background centered on the fovea. The focal electroretinograms were also elicited by half of an annulus placed above or below the macula. The diameter of the inner border of the annulus was 15 degrees and that of the outer border was 30 degrees. The structure of the optic nerve head and retinal nerve fiber layer thickness were evaluated by scanning laser ophthalmoscopy and laser scanning polarimetry, respectively.


RESULTS
The amplitudes of the focal photopic negative responses and the ratio of the focal photopic negative response/b-wave amplitude were linearly correlated with the corresponding retinal nerve fiber layer thickness in the superior/temporal and inferior/temporal regions (r = 0.43 to 0.47; P < 0.0001) but not in the temporal region. The focal photopic negative response amplitude and focal photopic negative response/b-wave amplitude ratio were also linearly and significantly correlated with the corresponding rim areas and cup/disc area ratio (r = 0.38 to 0.50, P < 0.0001).


CONCLUSIONS
These results strongly 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 photopic negative response in open angle glaucoma.
Department of Ophthalmology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka Iwate, Japan.
Kunifusa
K
Tamada
Shigeki
S
Machida
Taku
T
Oikawa
Hiroyuki
H
Miyamoto
Tomoharu
T
Nishimura
Daijiro
D
Kurosaka
D000368:Aged; D000369:Aged, 80 and over; D055253:Color Vision; D004596:Electroretinography; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D009898:Optic Disk / Q000473:pathology*; D012160:Retina / Q000473:pathology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D014794:Visual Fields