Wavefrontanalysis and Contrast Sensitivity after C-Cuts for Corneal Astigmatism
Kaymak H., Kremp K., Mester U.
Purpose: Correction of astigmatism with coreal arcuate incisions are safe and efficient procedures to reduce naturally occuring astigmatism as well as surgically induced astigmatism. Though the effects on sphere and cylinder (so called coupling-effect) are well known, changes in wavefront aberrations have not yet been investigated.
Method: 24 patients (age between 23-55 years) with idiopathic corneal astigmatism underwent paired arcuate-keratotomy with the diamond knife. All patients had complete ophthalmologic examination before and 6 weeks after surgery including wavefrontanalysis with Hartmann-Shack Sensor (Zeiss-Meditec) and contrast sensitivity testing with the Functional Acuity Contrast Test (F.A.C.T.) under photopic and mesopic conditions (with Ginsburg-Box).
Results: The mean vector-corrected surgically induced reduction of astigmatism was 2,61(SD 0,99). C-Cuts induced a mean negativ spherical aberration (Z4/0) of 0,09 micrometers and vertical coma of 0,12 micrometer (analyzed pupil diameter: 5mm). Contrast sensitivity was improved significantly under photopic and mesopic conditions with best corrected glasses, though there was a significant increase (+66%) of high-order aberrations.
Conclusions: C-Cuts induced not only spherical and cylindral changes but also high-order aberrations. The improved contrast sensitivity may caused by the induced negative spherical aberration which compensates the change from negativ
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