Clinical Ability of Pattern Electroretinograms and Visual Evoked Potentials in Detecting Visual Dysfunction in Ocular Hypertension and Glaucoma
Received 9 March 2005; accepted 26 October 2005. published online 09 January 2006.
Objective
To assess the presence of normal or abnormal pattern electroretinogram (PERG) and visual evoked potential (VEP) responses in patients with ocular hypertension or open-angle glaucoma (OAG).
Eighty normal control subjects (mean age, 51.77±6.04 years; 80 eyes), 68 ocular hypertension patients (mean age, 51.58±7.12; 68 eyes; intraocular pressure [IOP] < 18 mmHg under pharmacological treatment; Humphrey field analysis [HFA] 24/2 mean deviation [MD] > −2 decibels [dB]), and 84 OAG patients (mean age, 52.77±5.28; 84 eyes; IOP < 18 mmHg under pharmacological treatment; HFA 24/2 mean deviation between −2 and −23 dB) were enrolled.
Methods
Simultaneous recording of PERGs and VEPs using high-contrast (80%) 15′ checkerboard stimuli reversed at the rate of 2 reversals per second.
Main Outcome Measures
Pattern electroretinogram P50 and VEP P100 implicit times were considered delayed when exceeding the limit of mean values of controls plus 2 standard deviations (SDs). Pattern electroretinogram P50 to N95 and VEP N75 to P100 amplitudes were considered reduced when exceeding the limit of mean values of controls minus 2 SDs.
Results
Pattern electroretinogram: P50 implicit times were delayed in 58 of 68 (85.30%) ocular hypertension eyes and 83 of 84 (98.80%) OAG eyes; P50 to N95 amplitudes were reduced in 47 (69.12%) ocular hypertension eyes and 84 (100%) OAG eyes. Visual evoked potential: P100 implicit times were delayed in 58 (85.30%) ocular hypertension eyes and 84 (100%) OAG eyes; reduced N75 to P100 amplitudes were observed in 39 (57.35%) ocular hypertension eyes and 73 (86.90%) OAG eyes. Ocular hypertension eyes showed no significant correlations (Pearson test, P>0.01) between electrophysiological parameters and age, IOP before or under medical treatment, HFA, and corneal thickness values. Significant correlations (P<0.01) were observed in OAG eyes between electrophysiological results and HFA values. Pattern electroretinogram and VEP responses were normal in all control eyes.
Conclusions
Combined PERG/VEP recordings identified a large percentage of ocular hypertension eyes with impairment of the innermost retinal layers, notwithstanding normal optic disc morphology and normal HFA. In OAG eyes, PERG P50 to N95 amplitude and VEP P100 implicit time showed the highest sensitivity/specificity for the detection of a visual dysfunction. The presence of abnormal PERG and/or VEP responses did not allow a clearcut separation between ocular hypertension and OAG eyes.
1Fondazione per l’Oftalmologia G. B. Bietti–IRCCS, Rome, Italy
2Clinica Oculistica, Policlinico di Monza, Università Bicocca, Milan, Italy
ABSTRACT