The visually evoked potential (VEP), the recording of which has recently been made possible by the development of computer averaging techniques, is a gross electrical signal generated by the occipital region of the cortex in response to visual stimulation. It is more specific than the electroencephalogram (EEG) and more sensitive to changes in the visual stimulus; thus, it can provide ophthalmologists and vision researchers with information about the human visual system that is unavailable by other methods. Clinically, the VEP is of special value in the areas of refraction, infant acuity, diseases of the optic nerve, color blindness, amblyopia and field defects. Theory, techniques and instrumentation are described, and applications of the VEP to clinical situations and to vision research are discussed.

Adult↗

PubMedDate not supplied

The Pulfrich stereo-illusion as an index of optic nerve dysfunction.

A simple test based on the Pulfrich phenomenon may provide an indication of optic nerve dysfunction. When a small object swinging pendulum fashion is viewed binocularly by a person with one eye covered by a neutral density filter, the object appears to swing in an elliptical path. The patient with optic nerve dysfunction may see it this way without use of a filter. The Pulfrich theory is explained, clinical applications are discussed, and instructions for constructing a Pulfrich apparatus are given.

Evoked Potentials↗

PubMedDate not supplied

Pursuit eye movements in late-onset esotropia.

Horizontal, smooth pursuit eye movements were recorded from adults and children with infantile and late-onset esotropia using a remote, video-based, eye-movement recording system. Each subject monocularly tracked a 0.5-degree target moving back and forth on a video monitor at a constant velocity of 10 degrees, over a range of 12 degrees. Each subject's nasal and temporal gain (eye velocity/target velocity) was measured. Confirming the results of previous studies, we found that infantile esotropes had asymmetrical pursuit eye movements (nasal gain greater than temporal gain) while late-onset esotropes had symmetrical gains. However, unlike previous investigators, we found that half of the late-onset esotropes had impaired pursuit gain. The magnitude of the pursuit abnormality and the amount of refractive error were correlated--patients with the highest refractive error had the lowest pursuit gain.

Adult↗