A simple optics device may show higher sensitivity and reliability for measuring contrast sensitivity function (CSF) compared with a computer-based system, according to a study published in Ophthalmology and Physiological Optics.
“In most circumstances, CSFs are measured with a wall chart (such as the Pelli-Robson or CSV-1000), cathode-ray tube (CRT) oscilloscope or a computer monitor, which allows relatively simple electronic control of both spatial frequency and contrast,” the study authors explain. “These methods all tend to use very different stimuli and produce CSF curves that are often dissimilar in shape.”
Researchers included 21 participants (mean age, 28.95 years; 66.7% women) in the investigation and performed CSF evaluations using both the computer-based system and a simple optics device. The customized optical device used 520 nm lasers that had 2 integrating spheres with a 3.5° circular exit combined with a beam splitter. The team performed 2 sets of CSF measurements at 1.6, 3.2, 8, 16, and 24 cycles per degree at randomized special frequencies separated by 1 to 7 days and compared the sensitivity and reliability of both devices.
The shapes of the CSF curves differed between the methods, and the sensitivity of the simple optics device was approximately 3.5 times higher compared with the computer-based assessment.
The average coefficient of reliability was 0.27 for the computer-based system compared with 0.48 for the simple optics device. Participants tended to demonstrated higher sensitivity on the second evaluation day with both methods, but the study device showed high repeatability (r, 0.85) compared with computer-based system (r, 0.0), the report shows.
Investigators also note that the simple optics device did not return aberrant values, unlike the computer-based device. Excluding these outliers did improve the reliability of the computer-based device, according to the report.
“[C]hanging the stimulus presentation influenced both the shape and overall peak of the CSF and test–retest reliability,” according to the researchers. “This implies that varying the stimuli used to measure CSF also changes its prognostic value. Optimizing features (rather than just using a one-size-fits-all test or simply modifying the same features to make it faster, like the ‘quick CSF’22) to maximize the utility is likely a fruitful avenue for future studies using CSFs.”
The exclusion of individuals with poor visual function is an acknowledged limitation to the research.
Hammond BR Jr, Leathers TA, Wooten BR, Renzi-Hammond LM. Contrast sensitivity functions measured using simple optics and computer testing. Ophthalmic Physiol Opt. Published online April 10, 2023. doi:10.1111/opo.13141