S Beuel | PubMed Health

PubMed2000

Pupil perimetry using M-sequence stimulation technique.

PURPOSE: M-sequence stimulation technique allows mapping of the retinal function by multifocal electroretinographic (ERG) recordings. However, the information provided about visual field is limited to retinal function. Optic nerve diseases and diseases of the higher visual pathways usually show normal multifocal ERGs. Using pupillary responses instead of the electrical retinal responses might enhance the diagnostic possibilities of this system. The problems of local ERG recordings are very similar to those encountered in pupil perimetry: Local stimuli have to be dim to avoid or at least reduce stray-light responses. Dim stimuli, close to the absolute threshold, elicit only subtle pupillomotor responses. Therefore, techniques that are able to detect small focal responses are promising. METHODS: Pupillography was done by means of an infrared video camera and real time image processing (50 Hz) using a custom-designed videoboard in a personal computer (486). Recording conditions: The stimulus was presented on a monitor (75 Hz) in 26 cm distance from the patient's eyes. It contained 37 hexagons in a 25 degrees visual field. Each element changed between black (1.6 cd/m2) and white (160 cd/m2) after a binary M-sequence independently from other elements. Four thousand ninety six different stimulus pictures of 120-msec duration were shown during a single pupillogram recording. Thirty-seven local pupillograms were calculated in a cross-correlation of stimulus sequence and the pupil diameter. RESULTS: The pupillomotor fields in normals showed a shape and sensitivity distribution as known from conventional pupil perimetry techniques. Artificial paracentral scotomas (5 degrees) created by masking different locations could be demonstrated convincingly. Even in patients with optic nerve lesions it was possible to demonstrate visual field defects. CONCLUSIONS: Pupil perimetry using the M-sequence technique is a promising method of objective perimetry that may find its entrance into clinical application.

Adult↗

PubMed1998

A computer-controlled system for measuring dark adaptation and other psychophysical functions.

BACKGROUND: Psychophysical thresholds, including dark-adaptation functions and increment threshold sensitivities, are useful for the early detection and diagnosis of visual pathologies. However, few instruments have been designed or adapted for their routine clinical measurement. METHODS: Here we describe an instrument prototype designed to meet this need, which we refer to as the PULS (Programmier-barer Universeller Licht-Stimulator). The instrument is computer-controlled and fully automated. It allows direct control over target location, luminance, size, duration and temporal profile and over background luminance and spectral composition. It also incorporates an efficient and statistically rigorous strategy for determining threshold. RESULTS: We present examples of psychophysical functions-dark-adaptation curves, increment threshold sensitivities, estimates of temporal summation in the dark and during the time course of dark adaptation-which have been measured by the PULS prototype in normal observers and clinical patients. CONCLUSIONS: The PULS instrument provides an automatic and efficient means of measuring dark adaptation and other psychophysical functions. It determines threshold by a more rigorous and faster method than is conventionally employed in clinical adaptometry.

Adolescent↗