Browsing by Subject "Optical instruments"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Open Access
    Instrument for fast whole-field peripheral refraction in the human eye
    (Optica Publishing Group, 2022) Fernandez, Enrique J.; Sager, Santiago; Lin, Zhenghua; Hao, Jiangdong; Roca, Javier; Prieto, Pedro M.; Yang, Zhikuang; Lan, Weizhong; Artal, Pablo; Fernandez, Enrique J.; Física
    An instrument for fast and objective measurement of the peripheral refraction in the human eye is presented. The apparatus permits the automatic estimation of both defocus and astigmatism at any retinal eccentricity by scanning a near infrared beam. The design includes a Hartmann-Shack wavefront sensor and a steering mirror, which operate in combination with a compounded eyepiece for wide field operation. The basic scanning protocol allows the estimation of refraction in a circular retinal patch of 50 deg diameter (±25 from central fixation) in 3 sec. Combined with additional fixation points, wider retinal fields can be sampled to achieve a whole field. The instrument underwent calibration and testing, and its performance for real eyes was assessed in 11 subjects of varying age and refraction. The results show high repeatability and precision. The instrument provides a new tool for the investigation of peripheral optics in the human eye.
  • 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.