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Vrushali Korde, Xu Cheng, Ben Wooley, Chantal Brennan; Clinically Meaningful Contrast Sensitivity Difference for a Healthy Eye. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4614.
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© ARVO (1962-2015); The Authors (2016-present)
A +0.25D blur has been shown to be noticeable and clinically meaningful in a healthy eye population, but the resulting contrast sensitivity loss has not been determined. Measuring contrast sensitivity may provide additional insight to vision performance, therefore understanding a clinically meaningful difference in contrast sensitivity could be valuable for the development of vision correction devices. This work aims to tie together 2 clinical observations and optical modeling results to determine a clinically meaningful difference in contrast sensitivity reduction for a healthy eye.
The Quick Contrast Sensitivity Function (qCSF) method was used to measure the monocular Area Under the Log CSF (AULCSF) of healthy eye subjects with a best corrected contact lens and with a +0.25D spherical blur trial frame over the contact lens in 2 clinical observations.An eye model was used to simulate the monocular CSF under the conditions of best corrected refraction and +0.25D spherical blur. The eye model consisted of a +3.08D (myopic) eye with -0.3D cylinder power and spherical aberration of 0.09 µm RMS for a 6.0 mm pupil. This eye model was corrected with a -3D contact lens, resulting in residual amounts of uncorrected spherical power (+0.08D) and the previously mentioned cylinder power and spherical aberration. The polychromatic Modulation Transfer Function (MTF) of the eye model was then multiplied with the Neural Contrast Sensitivity Function (NCSF) model resulting in the simulated CSF.
In the first clinical observation, the AULCSF difference between the control lens and the control lens with +0.25D blur in a trial frame was 0.065. In the second clinical observation, the AULCSF difference between the habitual lens and the habitual lens with +0.25D blur in a trial frame was 0.056. Due to a difference between refraction distance and test distance, the +0.25D over the contact lens was in effect +0.17D. Therefore, the measured AULCSF differences were due to a combination of the +0.17D blur and the use of a trial frame. The reduction in AULCSF by +0.25D blur simulated by the eye model was 0.062.
By combining optical modeling with clinical observations, a confident estimate of a clinically meaningful loss in contrast sensitivity was determined to be approximately 0.06. In terms of percent loss of AULCSF, the model predicted a 3% loss, while the clinical results ranged between 4-5% loss.
This is a 2020 ARVO Annual Meeting abstract.
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