Electrophysiological evidence of early functional damage in glaucoma and ocular hypertension.
OBJECTIVE
The quantification of early retinal ganglion cell damage in ocular hypertension and glaucoma.


METHODS
Thirty subjects under treatment for open-angle glaucoma, 23 subjects with ocular hypertension, and 28 healthy subjects in a control group were investigated by monocular pattern electroretinogram (ERG), L&M (long and medium wavelength) cone ERG, and S (short wavelength)-cone ERG. The diagnosis of glaucoma was based on masked assessment of digital stereoscopic optic nerve head images by three glaucoma specialists. The optic nerve head and retinal nerve fiber layer was assessed by scanning laser ophthalmoscopy and optical coherence tomography.


RESULTS
All types of ERG had reduced mean amplitudes in ocular hypertension and open-angle glaucoma groups compared with the control group. In the ocular hypertension group, the N95 and the L&M-pathway photopic negative response (PhNR) were significantly attenuated (by 19% and 18% compared with the control group, respectively; by 30% and 22%, respectively, in the open-angle glaucoma group compared with the control group). In the subjects with open-angle glaucoma, the pattern ERG P50-N95 was found to be the most sensitive electrophysiological test, and the cup-disc area ratio, when examined by scanning laser ophthalmoscopy, was the most sensitive imaging parameter. Modest but not statistically significant correlations were found between the imaging and electrophysiologic parameters.


CONCLUSIONS
With disc appearance used for the classification of open-angle glaucoma and ocular hypertension, significant electrophysiological losses were found in both conditions. The modest correlation between the structural and electrophysiological measures suggests that these assess different aspects of the pathologic process; electrophysiology can be used to quantify retinal ganglion cell dysfunction that occurs before cell death.
School of Optometry and Vision Sciences, Cardiff University, Wales, United Kingdom. north@cardiff.ac.uk
Rachel V
RV
North
Adrian L
AL
Jones
Neville
N
Drasdo
John M
JM
Wild
James E
JE
Morgan
D000959:Antihypertensive Agents / Q000008:administration & dosage; D004596:Electroretinography; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology; D009798:Ocular Hypertension / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D009887:Ophthalmoscopy; D009898:Optic Disk / Q000473:pathology; D009901:Optic Nerve Diseases / Q000175:diagnosis / Q000503:physiopathology*; D051245:Retinal Bipolar Cells / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*; D041623:Tomography, Optical Coherence; D014795:Visual Pathways / Q000503:physiopathology
D000959:Antihypertensive Agents