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New LCD-based system provides precise contrast sensitivity
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SEATTLE — A new method of testing contrast sensitivity was shown to provide faster and more accurate measurements than traditional tests, according to a researcher here at Optometry’s Meeting.
Sarah Henderson, BS, a third-year student at Southern College of Optometry, and colleagues evaluated the Harris contrast test (M&S Smart System), a computer-based test using an LCD display that allows the operator to manipulate the contrast level with different optotype sizes, according to the study abstract.
The study results were presented in a poster at the meeting, and Henderson shared them in a “live poster session.”
Henderson explained that the Harris contrast test overcomes disadvantages of a paper chart, such as fading, and allows the clinician to manipulate the size of contrast level and optotypes.
Sarah Henderson
“You can go back and forth to pinpoint contrast sensitivity with the click of a button on the remote control,” she said
She said the goal of the study was to “assess the validity of acuity thresholds on fixed contrast level on the Harris chart as compared to the Bailey-Lovie low contrast chart.”
The study involved 53 healthy adults with a best corrected visual acuity of 20/20 or better and no ocular or systemic conditions that would decrease contrast sensitivity, she said. Average age was 29 years.
“We got a baseline of all subjects’ visual acuity with the high-contrast Bailey-Lovie chart, then measured with low contrast,” Henderson explained. “Then we went to the Harris contrast chart and presented a single optotype at fixed 18% Weber contrast level. Contrast thresholds measured at 20/400.
“We found that with low contrast Bailey-Lovie, the logMAR was -0.006 (+/- 0.11), which was a visual acuity equivalent of 20/19.725,” she continued. “With Harris, the logMAR was -0.0038 (+/-0.09) and a visual acuity equivalent of 20/19.825. There was no statistically significant difference between the two values.”
Henderson said contrast sensitivity testing is important to provide more information about a patient’s visual function and assess their condition better than standard measures of visual acuity, such as the Snellen chart. – by Nancy Hemphill, ELS, FAAO
Disclosure: Henderson reports no financial disclosures. M&S loaned the researchers the software