THE HUMAN ERG EVOKED BY A GANZFELD STIMULATOR POWERED BY RED AND GREEN LIGHT-EMITTING-DIODES

• Type: Article in International Scientific Journal
• Date: 1993

Authors

SPILEERS, W (Author) Other; Falcão-Reis F (Author) FMUP; SMITH, R (Author) Other; HOGG, C (Author) Other; ARDEN, GB (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: CLINICAL VISION SCIENCES

Vol. 8

Pages: 21-39

ISSN: 0887-6169

Indexing

ISI Web of Knowledge - 21 Citations

Scopus - 18 Citations

Other information

Authenticus ID: P-001-ND5

Abstract (EN): 1. A clinical ganzfeld stimulator is described. It illuminates the entire retina from a hemisphere of closely packed green and red light emitting diodes, which all point to the anterior nodal point of the eye. 2. All ERG electrodes may be used, all standard stimuli required for clinical recordings are available, including red flashes on green backgrounds of controlled intensity, and calibration in terms of quanta incident/square micron of retina/flash is simple. 3. Light intensity is electronically controlled over a continuous 6.5 log unit range, and in addition to brief flashes, long steps of light or dark intervals may be used to evoke ERGs. 4. Responses to brief flashes of dim green light evoke the scotopic threshold response and with brighter flashes, ''saturated'' rod responses with very large a-waves. 5. Longer steps evoke OFF responses. The conditions under which these are seen are described and the relationship between ON and OFF response amplitude, as a function of the intensity, duration and the duty cycle of a slowly-flickering light stimulus. In this way the relative contributions of photopic and scotopic mechanisms to the a- and b-wave evoked by steps can be determined. 6. Dim red flashes evoke a new cone response, analogous to the STR, as illustrated by recordings from patients deficient in rods or in cones, or with inner retinal damage. Brighter red flashes evoke cone b-waves and oscillatory potentials comparable to those produced by stroboscopes.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 19