From: Not all aberrations are equal: Reading impairment depends on aberration type and magnitude Journal of Vision. 2011;11(13):20. doi:10.1167/11.13.20 Figure Legend: Representation of the Zernike pyramid indicating the confusability of letters caused by each mode where a value of 1 indicates that letters are completely indistinguishable. Higher order aberrations are those with a radial order greater than 2. In (a), each aberrated letter is compared with the set of aberrated letters representing a subject attempting to recognize letters by looking for differences between the letters they are presented with. In (b), each aberrated letter is compared with the set of non-aberrated letters representing a subject attempting to recognize letters by making comparisons with known letter shapes. The Zernike modes that cause the most confusion between aberrated and non-aberrated letters are Z 2 0 (defocus), Z 4 ±2 (secondary astigmatism), and Z 5 ±3 (secondary trefoil). Date of download: 1/2/2018 The Association for Research in Vision and Ophthalmology Copyright © 2018. All rights reserved.