Visual function analyzer could provide pupillomerty, keratometry, and autorefraction assessment, allowing to acquire wavefront data and topography data simultaneously. Aberrometry presents larger applications than just enhancing the quality of the ablation zone in an excimer laser treatment. So the choice of the most appropriate machine depends mainly on the clinical practice. Making a practical comparison between the available devices is not an easy task because of the variety of principles used, such as ray tracing, Hartmann-Shack, Tscherning, and automatic retinoscopy. Wavefront sensors can be divided into 2 categories: outgoing and ingoing. Outgoing aberrometers operate by placing a point source of light on the retina and determining the shape of the wavefront emerging from the eye. Point source of light on the retina emits diverging spherical wavefronts that pass through the crystalline lens and the cornea to exit the eye. Ingoing aberrometers operate by examining how wavefronts external to the eye are altered as they pass through the optics of the eye. The Hartmann-Shack aberrometer is an outgoing wavefront aberrometer. The ray-tracing system is an ingoing aberrometry sensor. The purpose of this study is to provide a number of technical and practical parameters that may be useful in choosing an aberrometer for daily clinical practice. The total optical aberration of an eye is the sum of all rays entering and exiting the eye. Internal aberration refers to light rays that are mainly disturbed in the anterior segment. We measured high order aberration (HOA) of corneal, internal and total ocular using a KR-1W (based on Hartmann-Shack) and iTrace (based on ray tracing) to compare the difference and agreement of KR-1W and iTrace for measurement of HOA.
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