Abstract
Purpose::
This project was designed to examine the effects of optical blur on the visual performance and comfort of computer workers to determine whether optimizing their visual correction for computer work affects the accuracy and volume of their work.
Methods::
This intervention study examined a treatment (correction of optical blur) using a randomized, double-blind, placebo-controlled, crossover design. Inclusion criteria required subjects to be 19 yrs of age or more, have at least 0.50D uncorrected refractive error (URE) with their habitual correction in at least one eye, use a computer for 1 hr per day or more and have 20/40 or better corrected visual acuity in each eye. The primary outcomes of the study were visual comfort and productivity (correct output per hour). During two one-month study periods, subjects wore either lenses fitted for their best or habitual correction and completed 4 hours of testing during each period. Performance was measured by time and accuracy in completing editing and data entry tasks. A previously validated survey was used to assess symptoms. The study was approved by the IRB and adhered to the tenets of the Declaration of Helsinki.
Results::
There were 36 subjects (7 M, 29 F; mean age: 27.7 yrs) who demonstrated a mean URE of 0.80D (Std dev 0.57, range 0 to 3.03D) and estimated that they spent a mean of 5.1 hrs/day on the computer. Analysis confirmed a relationship between the visual symptom index and the number of eyes meeting the criteria of 0.50D RE (p=0.029; median values 86.7, 91.1 and 84.4 for 0, 1 and 2 eyes meeting the criteria, respectively). The subjects correctly edited 92.8% of the apostrophes in the 4518 total mean words (range 917 to 8143) edited during 1 hr and correctly entered 82.0% of the population values in the 938.4 total mean entries (range 278.7 to 1170) during 1 hr. ANOVA modeling of the data entry task suggested that hrs of computer use (p=0.011), total URE before the two eyes (p=0.032), the mean URE between the two eyes (p=0.010), the number of eyes meeting the criterion (p=0.001), the total magnitude of work (p=0.000) as well as the interaction between the number of eyes meeting the criterion and the total magnitude of work (p=0.001) were related to the total correct work per hr.
Conclusions::
These data suggested that the subjects were most comfortable and productive while working with low or absent degrees of optical blur in at least one eye.
Clinical Trial::
www.clinicaltrials.gov NCT00318045
Keywords: refraction • spectacle lens • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials