Effects of optical blur on visual performance and comfort of computer users
Background. The study examined the effects of optical blur on the visual
performance and comfort of computer workers. Since most workers have significant
degrees of optical blur, the study may elucidate improved methodology for workplace
comfort and function.
Methods. Since young and old workers experience blur from different sources,
the study incorporated two different designs. The study examined the correction of
optical blur using a randomized, double-blind, placebo-controlled, crossover design. The
primary outcomes of the study were visual comfort and productivity. In study one,
subjects were required to be 19-35 yrs of age, have at least 0.50D uncorrected refractive
error (URE) in at least one eye, use a computer for at least1-hr/day and have at least
20/40 corrected visual acuity (VA) in each eye. During two one-month study periods,
subjects wore either lenses fitted for their best or habitual correction and completed 4
hours of testing. In study two, subjects were required to be 40 years of age or older with
corrected VA of at least 20/40 and to require a near plus lens addition. Subjects
completed a total of 4 hours of testing in ten 15-minute periods with their near plus
prescription and a test pair of lenses (plano, +/-0.50 or +/-1.00D) with head free or fixed
on a chin rest.
Results. Analysis for the first study confirmed a relationship between the visual
comfort index (VCI) and the number of eyes meeting the criteria of 0.50D URE and the
task order (p = 0.0003, 0.0025) and suggested a trend for a similar relationship for correct
comfortable work (CCW, p=0.0149). For the second study, the VCI declined by 15.4%
(p = 0.0001) while total correct work (TCW) and CCW increased (36.4, 25.9%,
respectively; p=0.0001, 0.0094) over the 2.5 hr work period. Analysis supported a
hypothesis of a significant interaction of lens and head for VCI and CCW (p=0.0049,
0.0088, respectively) as well as a main effect for head position for TCW (p = 0.0069).
Conclusion. Subjects were most comfortable and productive while working with
low or absent degrees of optical blur in at least one eye.
School:University of Alabama at Birmingham
School Location:USA - Alabama
Source Type:Master's Thesis
Keywords:computers human engineering refraction ocular task performance and analysis vision low
Date of Publication: