Browsing by Subject "Adaptive optics"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Publication
    Open Access
    Adaptation to the eye’s chromatic aberration measured with an adaptive optics visual simulator
    (Optica Publishing Group, 2020) Fernandez, Enrique J.; Suchkov, Nikolai; Artal, Pablo; Fernandez, Enrique J.; Física
    Some aspects of vision after correcting the longitudinal chromatic aberration (LCA) of the eye are not yet completely understood. For instance, correcting the LCA notably alters the through focus visual acuity (VA) curve, but it does not improve the best VA obtained for the natural case. In this work, vision with corrected LCA is further investigated by using an adaptive optics visual simulator (AOVS). VA was measured continuously during 20 minutes in 5 subjects under both natural and corrected LCA conditions to explore possible adaptation effects. Low contrast VA as a function of time exhibited a consistent and significant boost of 0.19 in decimal scale after an average time of 10.9 minutes of continuous testing. For high contrast, only one subject showed a similar increase in VA. These results suggest that some LCA neural adaptation may exist, particularly for low contrast. This adaptation impacts the performance of vision under corrected LCA, and possibly prevents measurement for immediate visual benefit. The results have practical implications for the design and visual testing of optical aids, especially those correcting, or altering, the LCA.
  • Thumbnail Image
    Publication
    Open Access
    Comparison of binocular through-focus visual acuity with monovision and a small aperture inlay
    (2014) Schwarz, C.; Manzanera Román, Silvestre; Prieto Corrales, Pedro María; Fernández Martínez, Enrique Josua; Artal Soriano, Pablo; Física
  • Thumbnail Image
    Publication
    Open Access
    Impact of longitudinal chromatic aberration on through-focus visual acuity
    (Optica Publishing Group, 2019) Suchkov, Nikolai; Fernandez, Enrique J.; Artal, Pablo; Fernandez, Enrique J.; Física
    An enhanced adaptive optics visual simulator (AOVS) was used to study the impact of chromatic aberration on vision. In particular, through-focus visual acuity (VA) was measured in four subjects under three longitudinal chromatic aberration (LCA) conditions: natural LCA, compensated LCA and doubled LCA. Ray-tracing simulations using a chromatic eye model were also performed for a better understanding of experimental results. Simulations predicted the optical quality of the retinal images and VA by applying a semi-empirical formula. Experimental and ray tracing results showed a significant agreement in the natural LCA case (R2 = 0.92). Modifying the LCA caused an impairment in the predictability of the results, with decreasing correlations between experiment and simulations (compensated LCA, R2 = 0.84; doubled LCA, R2 = 0.59). VA under modified LCA was systematically overestimated by the model around the best focus position. The results provided useful information on how LCA manipulation affects the depth of focus. Decreased capability of the model to predict VA in modified LCA conditions suggests that neural adaptation may play a role.
  • Thumbnail Image
    Publication
    Open Access
    Simultaneous aberration and aperture control using a single spatial light modulator
    (Optica Publishing Group, 2019) Suchkov, Nikolai; Fernandez, Enrique J.; Martínez-Fuentes, Jose L.; Moreno, Ignacio; Artal, Pablo; Fernandez, Enrique J.; Física
    A method to simultaneously control aberrations and the aperture of an optical system using a single phase-only spatial light modulator was investigated. The experiment was performed using a liquid-crystal-on-silicon spatial light modulator (LCoS-SLM) within an adaptive optics system used for visual testing, although the method has broader applications in adaptive optics field. The performance of the technique was characterized through the estimation of the system’s modulation transfer functions (MTFs) by using a random chart method. MTFs obtained from the phase modulation-based approach were compared with those from using a real aperture (diaphragm). The areas under the MTFs for the two conditions were similar up to 98%, confirming that the low-pass filter effect associated to the size of the entrance pupil was similar for the phase-modulated pupil and the physical pupil. As an example of application, both aberrations and pupil were controlled by a single phase-only modulator to study the through-focus visual performance in real subjects. Limitations and possible enhancements of the presented method were also discussed. The presented technique reduces complexity and cost of adaptive optics systems. It opens the door to new experiments by allowing dynamic modulation of aberrations and apertures of any shape.
  • Thumbnail Image
    Publication
    Restricted
    Wide-range adaptive optics visual simulator with a tunable lens
    (Optica Publishing Group, 2019-04-04) Fernandez, Enrique J.; Suchkov, Nikolai; Artal, Pablo; Fernandez, Enrique J.; Física
    An adaptive optics visual simulator (AOVS) with an extended dioptric range was developed, allowing measuring and correcting aberrations in a majority of highly ametropic eyes. In the instrument, a tunable lens is used for defocus correction, while a liquid-crystal-on-silicon spatial light modulator is used for compensating or inducing any other aberration. The instrument incorporates a digital projector, which uses a micromirror array to display the stimuli. A motorized diaphragm enables operation for any physiological pupil size. A full description of the instrument and its calibration are provided, together with the results obtained in seven highly myopic subjects with refraction of −7.2 1.8 D (mean SD). Refraction obtained with the instrument was compared to the standard refraction prescribed by trial lenses. When using the refraction obtained by the AOVS, the visual acuity (VA) exhibited an average increase of 0.21 (decimal scale). The visual impact of correcting high-order aberrations is presented in three subjects, whose VAs slightly improved with the correction. High myopes are able to benefit from the improved refraction assessment. The new instrument creates a possibility for a wide number of new experiments, especially for eyes exhibiting large refractive errors, where previous AO instruments failed to operate.