Working Hypothesis: The blue-light blocking lens has no effect on the contrast sensitivity, accommodative response, color vision, and subjective grading of the quality of life and vision. Purpose: To determine and compare the visual performances after wearing the blue-light blocking lenses in participants with and without presbyopia. Methods: One hundred and sixty computer users (computer usage \>2 hours/day) with (n=120, aged \>40years) and without presbyopia (n=40, aged 18-35 years) will be recruited. Three pairs of ophthalmic lenses will be prescribed for the participants, in which one pair of them will be the blue-light blocking lenses (StressFree, Swisscoat, HK). The lenses will be used for intermediate vision (i.e., computer usage) in presbyopic group, and for distant vision in non-presbyopic group. The adaptation period for each pair of lenses will be 1 month. The pre- and post-treatment contrast sensitivity, accommodative response and color vision will be measured. The participants will also be asked to complete questionnaires about their quality of life and vision, and the performances of these ophthalmic lenses. Significance: The blue-light blocking lens reflects the short-wavelength lights and protects the retina from "blue-light hazards"; however, blue lights are essential for various visual function and circadian rhythms. This study will evaluate the impact of the blue-light blocking lenses on visual function and quality of life, and determine whether the blue-light blocking lenses are good choices for extra ocular protection.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
80
Contrast Sensitivity as Assessed by Mars Contrast Sensitivity Chart
Contrast sensitivity was measured using the Mars contrast sensitivity letter chart (Mars Perceptrix, Chappaqua, NY). One out of three charts differing in the letter combinations was selected randomly in order to avoid memorization of the charts. The chart was placed at 50 cm with each letter subtended 2° visual angle. We followed the recording procedures as specified by the manufacturer: participants were instructed to read the letters from high to low contrasts and the test ended when two consecutive errors were made. The contrast sensitivity was scored as the log contrast sensitivity of the last correct letter minus 0.04 log unit for every prior error. The test was administered under normal (room illumination, 400 lux) and glare conditions. A brightness acuity tester set at its medium light intensity level (100 foot lamberts) simulated the glaring condition. A higher mean indicates improved contrast sensitivity.
Time frame: Every 1-month interval from the date of randomization, up to 3 months
Color Vision as Assessed by the Farnsworth Munsell 100 Hue Test
The Farnsworth Munsell 100 hue test (X-Rite, USA) was used to evaluate colour vision. Each of the four trays consisted of 21 movable caps. Participants were asked to sort the randomly arranged caps following the hue order from the first to the last fixed caps. The total error score was calculated, as documented in the instruction manual, to quantify the accuracy of color discrimination. There are no defined endpoints to the "total error score" range. A lower score indicates improved color discrimination ability.
Time frame: Every 1-month interval from the date of randomization, up to 3 months
Self-assessment of Lens Performance Through Questionnaire
After each monthly wearing period (visits 3-5), the participants' lens performance, night vision quality and sleep quality (total 13 questions) were assessed subjectively using a questionnaire (scoring from 1 \[very unsatisfactory\] to 5 \[very satisfactory\]). At the end of the study, the participants were asked to choose their preferred lens type among the three pairs of lenses based on their subjective feeling of the "best lens type" (i.e., either clear lens, yellow tinted lens or blue-filtering coated lens). To make it clear and simple, here we only present the data on the participants choice of their preferred lens type (i.e., simply choosing the "best lens" among clear lens, yellow tinted lens or blue-filtering coated lens).
Time frame: Every 1-month interval from the date of randomization, up to 3 months
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