Repeatability and reliability of ocular aberration measurements in contact lens wear

Background To assess repeatability and within- and between-observer reliability when measuring ocular aberrations with and without soft contact lens wear. Methods The irx3 aberrometer was used to measure second to tenth radial order aberrations on 13 subjects with and without their habitual soft contact lenses. This was first performed by one observer, who took three separate measurements to determine repeatability. In addition, two observers each took a set of three measurements on two occasions, to determine within- and between-observer reliability. Data were normalized to a constant pupil size for all measurements made on each subject. Results There was no difference in repeatability with or without contact lenses for Zernike polynomial numbers 3–20. There was no difference between within- and between-observer relative reliability either with lenses (t = 1.9, p = 0.07) or without lenses (t = 1.1, p = 0.29). However, both within-observer and between-observer reliability were worse when lenses were worn (t = 3.6, p = 0.0009 and t = 2.8, p = 0.0074, respectively). Conclusion The reduction in within- and between-observer reliability when measuring aberrations in contact lens wearers may be due to variability resulting from a variety of factors, such as lens flexure, lens movement, lens decentration and reduced stability of the pre-lens tear film.