USE OF CONTRAST SENSITIVITY AS A MEASURE TO EVALUATE GLARE CAUSED BY DIFFERENT LIGHT SOURCES

To learn more about the usefulness of contrast sensitivity as a glare assessment measure after exposure to different light sources.

Glare measurement is useful as it is a cause of impairment of visual function.

An experimental study was carried out to evaluate contrast sensitivity (CS) at low (1.5 cycles/degree) and high (12 cycles/degree) spatial frequency using the FACT test in a mesopic environment under three light conditions: no glare (baseline) and two glare sources of different intensity: 0.07 lux (glare condition 1) and 0.13 lux (glare condition 2). In addition, measurements were made to evaluate pupil diameter without glare (baseline). The de Boer questionnaire was also used for the subjective assessment of discomfort glare. Subjects over 18 years old without eye diseases were included.

Forty subjects were recruited with a mean age of 43.39 years and a mean spherical equivalent of -1.37 diopters. The mean mesopic pupillary diameter was 6.83 millimeters. High-frequency CS scores were larger than low-frequency CS scores in the baseline and glare 2 conditions. Although no overall significant differences in high- or low-frequency CS scores were found among no glare, glare 1 and glare 2 conditions, age was found to significantly explain differences in high-frequency CS scores between the no glare and glare condition 1 (p = 0.027), and in low-frequency CS scores between no glare and glare 2 condition (p = 0.046). No significant differences in discomfort glare measured by the de Boer scale were found between glare condition 1 and 2.

Low-intensity illuminations, appear not to cause either considerable visual impairment nor perceived discomfort glare globally. Age is a factor that explains the differences that occur in high spatial frequencies when faced with glare. Contrast sensitivity could be useful as patient evaluation and selection in refractive surgery or indication for cataract surgery.