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Wide field 2-D rapid scanning peripheral refractor


Purpose : To design, build and validate a new optical instrument to measure ocular refraction and aberrations rapidly in a two-dimensional (2D) wide field. Existing peripheral refractors are constrained to limited meridians, therefore requiring several visual fixations at different points to complete an actual 2D map, making them impractical for clinical use.

Methods : The instrument combined the scanning of 850-nm laser beam with a Hartmann-Shack (H-S) wavefront sensor. A multielement eyepiece was designed for wide field operation. A steering mirror scanned the beam generating a flying spot on the subject’s retina. The light backscattered from the retina was de-scanned by the steering mirror and redirected to the H-S relay for optical measurements. The visual fixation stimulus was generated by rotating the steering mirror, forming a flickering disc of 0.5 deg diameter. The stimulus was intermittently presented for 150 ms every 300 ms. During the time off, the beam was sequentially scanned on the retina, and refraction/aberrations were estimated at 98 Hz. Trial lenses were measured at different eccentricities for prior calibration. Accordingly, residual field aberrations of the apparatus were computationally compensated. A group of 10 young normal subjects participated in the first series of measurements.

Results : The instrument estimated the magnitude and orientation of trial lenses within a precision of 5 %. The basic operation mode in real subjects obtained the refraction in 50×50 deg field (88 sampled points, 5 deg step), with a single fixation point, in 3 sec. With 2 fixation points at ±15 deg horizontal, refraction distribution in 80×50 deg field could be obtained. Other protocols included high density, 1 deg step, at any selected meridians. Retinal sampling can be customized and adapted to virtually any clinical need. 2D refraction and aberration maps were obtained in the group of subjects.

Conclusions : The new scanning peripheral refractor permitted the accurate, programmable, and rapid measurements of peripheral optical parameters of the eye. A single fixation point provided data in a field of 50×50 deg in 3 sec. The enhanced capabilities of this instrument, such as wide angle and speed would allow its use in the clinic for the characterization of peripheral optics as a clinical tool in myopia management.

This abstract was presented  (poster) at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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