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Can scattered light improve visual performance?
Author(s) -
PATTERSON EJ,
BARGARY G,
BARBUR JL
Publication year - 2012
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2012.4281.x
Subject(s) - mesopic vision , glare , luminance , illuminance , optics , contrast (vision) , pupil , adaptation (eye) , retina , intensity (physics) , flicker , retinal , physics , optometry , photopic vision , computer science , materials science , ophthalmology , medicine , layer (electronics) , composite material , operating system
Purpose Light scattered by the media within the eye reduces object contrast and can also cause visual discomfort, in the presence of bright light sources. The addition of uniform veiling light over the retina can, however, change retinal sensitivity by increasing retinal illuminance. The extent to which reduction of target contrast and changes in retinal sensitivity caused by the presence of a glare source affect contrast acuity (CA) thresholds remains to be established. We investigate how CA is affected by glare source intensity, surround luminance and test target location on the retina. The aim is to determine the range of glare source intensity and background adaptation level that can improve visual performance. Methods 45 subjects with normal vision were investigated. A psychophysical flicker‐cancellation test (Ophthalmic & Physiological Optics, 17, 171, 1997) was used to measure the amount and angular distribution of scattered light in the eye. CA thresholds were measured using the Contrast Acuity Assessment test (ASEM, 74, 551‐559, 2003). Three glare source intensities (i.e., 0, 1.35 and 19.21 lm/m^2 in the pupil plane), three eccentricities (5, 10 and 15 degrees), and three background luminances (1, 2.6 and 26 cd/m^2) were investigated. Results CA thresholds were measured for the test target / glare source parameters listed above. In addition, the scatter function of the eye was assessed for each subject and the measured parameters were used to predict the effect of veiling glare on CA thresholds. Conclusion Low intensity glare can improve CA in the high mesopic range. High intensity glare yields increased thresholds, but this loss of contrast sensitivity is, in general, smaller than predictions based on veiling glare luminance caused by forward light scatter in the eye.