Pattern Evoked Cortical Potentials and Automated Perimetry in Chronic Glaucoma. In: Spekreijse H, Apkarian PA, editors. Visual Pathways. Dordrecht: Springer Netherlands; 1981. pp. 87-94. [DOI: 10.1007/978-94-009-8656-5_8]

The effect of stimulus size on human cortical potentials evoked by chromatic patterns

The effect of stimulus size on the pattern onset-offset visual evoked potential elicited with stimuli of two different wavelengths is studied under intensive yellow adaptation: (1) The onset response obtained with a 460 nm pattern is of negative polarity (N1) and saturates in amplitude with a stimulus radius of 7 deg. The onset response obtained with a 550 nm pattern is of positive polarity and continues to increase up to the maximum size (32.2 deg). (2) The peak time of N1 (460 nm) decreases with increasing stimulus size, that of P1 (550 nm) remains constant. These results are discussed as reflecting either varying retinal and brain anatomy, or cone activity, color-opponent activity, or luminance contrast activity.

The pattern-evoked electroretinogram (PERG): age-related alterations and changes in glaucoma

Pattern-onset electroretinograms (PERGs) were studied in 147 normal subjects of different ages (14-79 years) and in 110 eyes of 65 patients with glaucoma or ocular hypertension. The responses showed an increase (P less than 0.001) in peak latency with increasing age and a decrease (P less than 0.001) in amplitude which approximately parallels the loss of ganglion cells estimated by other authors. Many glaucoma eyes showed a loss of the normally present spatial tuning. In the age group above 50 years 50% of the onset responses were significantly diminished and the peak latencies were not significantly different. A negative correlation (P less than 0.001) was found between the size of the PERG and the cup/disc ratio and a positive correlation (P less than 0.001) with the area of the neuroretinal rim of the optic disc. The PERG decreased (P less than 0.01) with increasing visual field losses.

Electrophysiological assessment of visual deficit in glaucoma

Steady-state visual evoked potentials (VEP(S)) in response to contrast reversed vertical grating patterns and uniformly flickering fields were recorded in patients with glaucoma and in controls. In steady-state VEP(S), responses to temporal and spatial aspects of visual stimuli are combined, which makes the assessment of visual function dependent on their interaction. Fourier analysis of pattern reversal VEP waveforms showed marked deficits in temporal processing of spatial contrast for glaucoma patients. The degree of glaucomatous damage, as manifested by greater optic nerve atrophy and visual field loss, was correlated with progressive disruption of the VEP waveform and progressive failure in temporal processing of spatial contrast patterns. The VEP(S) in response to uniform full-field flicker showed no deficit.

Contrast sensitivity and pattern visual evoked potential in patients with glaucoma

Contrast sensitivity and pattern visual evoked potential (VEP) were measured in cases of ocular hypertension and primary open-angle glaucoma at various stages. The visual field of each eye was examined quantitatively and the retinal nerve fiber layer and optic disc were precisely assessed with magnified stereoscope fundus photography. This study revealed that contrast sensitivity of the eyes with glaucoma was within the normal range in the very early stage of the disease. As optic nerve damage advanced, high- or low-frequency loss developed. Further optic nerve damage produced a level type of loss. Pattern VEPs also showed increasing abnormalities as glaucomatous optic nerve damage progressed. Measurements of contrast sensitivity and pattern VEP were found not to be as sensitive as quantified precise visual field measurement or color stereoscopic fundus photography for detection of minor optic nerve damage in cases of early glaucoma. These methods may be useful, however, as an objective and subjective monitor of progression of optic nerve damage in glaucoma.

Pattern electroretinogram and visually evoked cortical potentials in glaucoma

Electroretinograms (P-ERG) and cortical potentials (P-VECP) evoked by checkerboard patterns were examined in patients with defects of the ganglion cell and nerve fiber layers due to glaucoma. Only a few patients exhibited a prolonged latency in the P-VECP, whereas in the P-ERG all patients with papillary and visual field defects revealed a significantly attenuated amplitude. Since there is a substantial fluctuation in the assessment of papillary excavation and visual field, the P-ERG offers a further means of evaluating and follow-up of retinal function in glaucoma patients.

Comparative material on automated and semiautomated perimeters-1983

In reviewing all the responses from the private practitioners and clinicians in Departments of Ophthalmology throughout the United States and Canada, it would appear that the majority of individuals are quite happy with the automated perimeters they have purchased. Clinicians should be aware that this is a rapidly changing field and several devices which were previously available are no longer being manufactured. In addition, because of the competition which has recently developed in the automated perimetry industry, prices are continuing to come down. Some practitioners have been unhappy with the fact they paid a higher price for a device which is currently selling at a lower price. However, a similar phenomenon has happened in the computer world and is to be expected as competition increases. The major problems which seem to be of concern to all ophthalmologists, are the difficulty in interpreting data and the management of the data. We believe one of the major frustrations of all practitioners using automated perimeters relates to the fact that this is a totally new technique, which requires time and practice to gain familiarity. In general, it would appear that most of the practitioners have been happy with the service provided by various companies, although there are a few exceptions. Read the enclosed responses and develop your own conclusions. We hope you find the information useful.