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© 2015 Journal of ophthalmic and Vision research | published by Wolters KluWer ‐ medKnoW Sir, Recently, a new aberrometer, the iDesign advanced Wavescan studio (Abbott Medical Optics, Santa Ana, CA, USA) has been launched for commercial use. This device is considered as a new, upgraded and more sensitive version of the Wavescan aberrometer (Abbott Medical Optics, Santa Ana, CA, USA). It has five times greater resolution, encompassing over 1,250 data points through a 7.0‐mm pupil as compared to 240 points for the Wavescan.[1] However, it remains to be seen if this increase in sensitivity would hamper instrument repeatability by picking up extra signal noise, especially during testing of wavefront aberrations, which are variable to some extent. In this consecutive case series, we measured the single user, single session repeatability of wavefront and other anterior segment measurements by iDesign in 100 refractive surgery candidates with no ocular morbidity except for refractive errors. The study had institutional review board approval and followed all tenets of the Declaration of Helsinki. Informed consent was obtained from all candidates. All candidates underwent a detailed evaluation and those with topographically evident keratoconus, dry eye, any previous surgical intervention in the eye or corneal scars/irregularity were excluded. All measurements were obtained by a single experienced user (DS) on the iDesign aberrometer. The candidates waited in the dedicated examination room for 30 minutes with eyes closed and the room lights shut off. Then the tests were carried out in dark room conditions. A five‐minute rest with the eyes closed was given between each measurement. The data is then analyzed by the instrument software, which looks for usable iris registration, wavefront data, and corneal topography data. The review screen shows a green icon for all these three data when measurements are practical for treatment or analysis. Three such consecutive ‘good’ measurements were taken. The right eyes were used for analysis. The data were noted and analyzed for a 6‐mm pupil diameter. Even though the machine provides output till 6th order aberrations for individual polynomials, the analysis was limited up to the 4th order to maintain clinical relevance and ease of interpretation as beyond 4th order, most values were exceedingly low. Polar Zernike coefficients were used for the study. All data was then transferred as jpeg images and manually entered into an MS Excel (Microsoft, Richmond, VA, USA) sheet. The data was then transferred to SPSS software version 16.0 (SPSS Inc., Chicago, IL, USA) for analysis. Mean and standard deviation of data for the three measurements (of 100 eyes) as well as the pooled data (n = 300) were derived. Analysis of variance was used to evaluate differences among the three measurements. The intra‐subject variation was assessed by the parameters described by Altman and Bland, including intra‐subject standard deviation (Sw) of the three consecutive measurements, intra‐subject precision (1.96 × Sw) and intra‐subject repeatability (2.77 × Sw).[2] The means, standard deviations, 95% confidence intervals of means and the range of data are detailed in Table 1. Mean values for measurement in the three groups were comparable (ANOVA P > 0.05 for all measurements, Table 1). Intra‐subject standard deviation (Sw), repeatability and precision values are presented in Table 2. The intraobserver Sw was 0.25 diopter (D) for sphere and 0.08 D Letter

Single session, intra-observer repeatability of an advanced new generation Hartmann-Shack Aberrometer in refractive surgery candidates