OBJECTIVE ASSESSMENT OF DISCOMFORT GLARE USING ELECTROMYOGRAPHY

Title OBJECTIVE ASSESSMENT OF DISCOMFORT GLARE USING ELECTROMYOGRAPHY
Author, Co-Author Mark Bullimore, Sam Berman, Ian Bailey, Robert Jacobs
Topic
Year
1992
Day
Saturday
Program Number
2:00 pm
Room
Ireland B
Affiliation
Abstract We have developed an objective method which uses electromyographic (EMG) responses from the orbicularis muscles to provide an objective correlate of glare discomfort. For 20 subjects, discomfort glare was assessed under three conditions: low illumination (wall luminance 0.5 cd/m^2), medium illumination (wall luminance 12 cd/m^2), and medium room illumination with a smaller diameter glare source. The glare source was a projector beam 2 deg in diameter (1 deg for the smaller source condition) and 11 deg to the right of fixation and the luminance was varied using neutral density filters. Six different glare luminance levels were presented for 2 second periods. Each glare level was presented six times in a randomized order giving 36 presentations. Subjects fixated a monitor at 1 meter (8 x 10 deg, luminance 69 cd/m^2). For each stimulus presentation, discomfort was assessed using both objective and subjective techniques. For the objective method, Fourier analysis of the EMG trace yielded a power spectrum which was integrated to provide the measure of EMG activity. Frequencies below 10 Hz and at 60 Hz were discarded to avoid contamination by blinks or by power line noise. A two second EMG sample during exposure to the glare source was compared to a sample prior to exposure to provide an index of discomfort. For the subjective method, subjects indicated the level of discomfort by marking a Visual Analog Scale (VAS) punctuated with four descriptors of discomfort level: perceptible, annoying, disturbing and intolerable. The two techniques were compared by plotting EMG activity and VAS rating as a function of luminance. For individual subjects, we found increasing EMG activity with increased subjective discomfort. The glare source consistently produced the greatest discomfort under low background illumination and the least discomfort in the medium room illumination/smaller source condition. We conclude that our EMG technique provides a reliable obj
Affiliation of Co-Authors
Outline