Clinical validation of an adaptive optics visual simulator

Laburpena

Adaptive optics visual simulators have been widely used in research laboratories for various applications within the visual sciences, however, their use in clinical practice has been limited. Recently, an Adaptive Optics Visual Simulator (VAO, Voptica S.L) has been commercially introduced as a medical device for clinical use. This visual simulator performs objective measurements of the aberrations of the human eye, as well as subjective refraction, visual acuity and simulation of different optical profiles, among other functions. Generally, before a new instrument is used in clinical practice, it must be validated to check its performance. When it is designed and developed, clinical validation must demonstrate that the objectives and safety intended by the manufacturer are achieved, as well as that the use and applications of the product give the expected results. This verification or validation is usually judged on the basis of how accurate (repeatable and reproducible) the measurements of the new medical device are and also the agreement with the gold standard (GS), in order to replace other medical devices and methods conventionally used in visual screening and diagnosis with more advanced technology. The Adaptive Optics Visual Simulator, VAO, is an instrument that as a whole is capable of performing objective optical measurements and subjective visual testing. This instrument incorporates an aberrometer with a Hartmann-Shack type sensor that measures the wavefront of the eye, thus obtaining the objective refraction and high order aberrations (HOA). A liquid crystal on silicon (LCoS) that acts as a spatial light modulator, allows for correcting or inducing any optical phase profile, being able to optically place visual stimuli at any required distance. In the same way, it also has an integrated an OLED display to present visual stimuli (optotype) to the patient. The instrument also allows to perform subjective refraction and can induce and correct, different amounts of high order aberrations, as well as various optical profiles. The main objectives of this thesis are: 1. To assess the precision (repeatability and reproducibility) and the agreement between examiners of objective refraction and high order aberrations taken with VAO, to be able to determine the degree to which repeated measurements under unchanged conditions and repeated measurements performed by different operators shows similar results. 2. To validate the subjective refraction and visual acuities taken with VAO by assessing the agreement between examiners and by comparing the results with gold standard procedure, to measure the accuracy of VAO and the agreement with the GS. 3. To study how depth of focus changes as a function of spherical aberration and is different for each person. For this purpose, different amounts of negative SA were induced, and trough-focus visual acuity was performed to investigate the potential benefit of SA customization. The analysis of the results of the different studies performed in this thesis suggests that VAO is able to provide consistent and reliable measurements of objective refractive parameters as well as of high order aberrations and RMS between measurements performed by the same examiner and those performed between two different examiners. The results obtained in the agreement of subjective refraction between examiners have similar or even better values than the reproducibility of subjective refraction with standard methods (trial frame and phoropter), which indicate a good correlation between both examiners. As for the agreement with the trial frame (GS), there were no significant differences in the subjective refraction and BCVA measurements between VAO and the gold standard used, having a good correlation between them. It follows that the two methods compared are analogous and can be interchanged without any detriment to the reliability of the measurements. Thus, subjective refraction found with VAO can be used for prescribing glasses and as a baseline to simulate any optical profile and to customize the selection of the ablation and the IOL design in refractive surgery. Finally, the induction of different values of negative spherical aberration with VAO increased the depth of focus of the subjects. However, the behavior was different for each one (high inter-subject variability). With this study, it has been shown that VAO can be used to determine the benefit in visual acuity by inducing different amounts of spherical aberration and that this benefit depends on each subject. With these findings described above, we can conclude that VAO, a Hartman-Shack wavefront aberrometer that objectively measures total low and high order aberrations of the eye and an instrument capable of performing subjective refractions and inducing any optical pattern or aberrations while performing visual tests, has been successfully validated.