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Jinrong Li, Jin Yuan, Fang Hou, Michael Dorr, Zhong-lin Lu; Deficient Contrast Sensitivity Function in Regular Astigmatic Eyes with Normal or Corrected-to-Normal Visual Acuity. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4214.
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The contrast sensitivity function (CSF) provides a more comprehensive measure in functional vision compared to visual acuity. This study investigates the visual quality of regular astigmatic subjects with normal or corrected-to-normal visual acuity by evaluating their CSF and ocular optical performance.
A total of 40 eyes of patients (ages 15-29 years old) with regular astigmatism either with normal acuity or corrected-to-normal acuity with their full spectacle corrections, and 34 healthy eyes of individuals (ages 22-30 years old) without astigmatism participated in this study. The cutoff spatial frequency (cutoff SF) and the area under log CSF (AULCSF) in CSF were derived with the quick CSF method (Lesmes, et al, 2010; Hou, et al, 2015). The MTF cutoff frequency (MTFcutoff), Strehl2D ratio, OQAS values (OVs) at 100%, 20%, and 9% contrasts, and objective scatter index (OSI) were used to assess the optical quality of the studied eyes by the Optical Quality Analysis System (OQAS).
The average astigmatism was 2.56±0.84 D (1.50-4.50 D) in the astigmatic eyes. The MTFcutoff (29.28±15.55 c/d) of the astigmatic eyes was significantly lower than that of the normal eyes (40.48±11.68 c/d) (p<0.001). The Strehl2D ratio was less in astigmatic eyes (0.18±0.09) than that of the normal eyes (0.23±0.08) (p<0.01). OV 100%, 20% and 9% and OSI were significantly smaller in the astigmatic eyes compared to normal (all p<0.05). Moreover, the cutoff SF in the astigmatic eyes was significantly lower (14.36±4.32 c/d) than that in the normal eyes (17.82±5.48 c/d) (p < 0.001). The AULCSF was reduced in astigmatic (1.15±0.28) versus normal eyes (1.35±0.17) (p<0.01). Most importantly, for patients with regular astigmatism, although visual acuity was not correlated with any optical performance measure, the AULCSF negatively correlated with the degree of astigmatism and the Strehl2D ratio (r=-0.3223 and -0.3745; p<0.05), and the cutoff SF correlated with the degree of astigmatism (r=0.3553; p<0.05).
Astigmatic eyes exhibited deficient contrast sensitivity function and optical transmission, even under full optical correction. The contrast sensitivity function is an important clinical management factor in assessing astigmatism correction in addition to visual acuity, even for individuals with normal uncorrected visual acuity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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