Changes in Foveal Fixation Axis Position Between Seated and Supine Postures and Their Potential Applications in Refractive Surgery

The correct centration of the ablation in laser refractive surgery is an unresolved classic challenge. This is usually performed at the pupillary center or corneal vertex, but ideally should be done with the point through which the patient's eye truly aligns when looking. Aligning the ablation with this axis is believed to yield the most accurate and effective refractive outcomes. This study proposes the use of a new device designed to center ophthalmic lenses, specifically progressive addition lenses, with the foveal fixation axis (FFA). This device showed an acceptable repeatability and users prescribed with progressive addition lenses with its measurements have an elevated adaptation rate and satisfaction. Because foveal fixation axis measurements have proven to be suitable for progressive addition lenses adaptation, it should be of interest to analyze whether these measurements can also be used as a proper reference in refractive surgery procedures, helping to improve centration of the laser ablation. Preoperative refractive surgery exam includes measurement of corneal and pupil characteristics that are conducted with the patient upright, but surgery is performed with the patient lying down, and a rotational movement of the eye has been described with this change of position. The purpose of this study was to analyze the change in FFA position with the change of the patient's position from seated to supine position, discussing the impact on refractive surgery procedures.