Wavefront Sensor with Astigmatism Correction for Measurements on the Human Eye

Abstract: When conducting experiments on the human eye it is sometimes required to correct some form of astigmatism. A fexible and cost effective way to achieve this is using two identical cross-cylinder lenses, as described in the article ‘Adaptive Astigmatism-Correcting Device for Eyepieces' by Arines and Acosta. When rotating these lenses the strength and angle can be adjusted to correct for different types of astigmatism.The measurements were made on two identical SR = +2 D, CR = - 4 D lenseson rotating mounts. A Shack-Hartmann wavefront sensor detected the change in a beam of collimated light directed through the lenses. Two types of measurements were conducted, to record the results of just the relative angle between the lenses and to find the aberrations the lenses themselves introduce to the system in combination with rotation. The two-lens-system we created adhered well to the theory and the results obtained by Arines and Acosta, although we obtained a slight variation in our values. The minimum cylindrical strength was close to -9 D and the aberrations were very small (< 0:01 μm). The reasons for these systematic errors are discussed but for the purposes of aiding in visual optics research this solution is well suited for its ease of use, and cost effectiveness.