Comparison of Two Wavefront Autorefractors: Binocular Open-Field versus Monocular Closed-Field

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Comparison of Two Wavefront Autorefractors: Binocular Open-Field versus Monocular Closed-Field

Eye Refract System

The Eye Refract system (Luneau Technology; Chartres, France) is a binocular open-field aberrometer combined with a phoropter. The Eye Refract incorporates two Hartmann–Shack sensors that perform objective refraction in both eyes at the same time. The wavefront metric used for the objective refraction determination is based on the principle of equivalent quadratic, using the method of paraxial curvature matching proposed by Thibos et al. [25] This method considers the high-order aberrations analysis up to 4th order, using the Zernike coefficients  and  for MSE determination,  and  for J0 determination, and  and  for J45 determination The Eye Refract measures the wavefront under physiological pupil conditions, and it recalculates the refractive parameters for 3 mm. If pupil size is equal to or less than 3 mm, the Eye Refract provides the values for its exact size. The Hartmann–Shack sensors use a near-infrared light of 800 nm, and the pitch of the microlens array is 0.1 mm.

Refractive Parameters

Refractive parameters were analyzed in terms of mean spherical equivalent (MSE) and vertical and oblique cylindrical vectors (J0 and J45) with the method proposed by Thibos et al. [27]. The following expressions were used to calculate MSE, J0, and J45:

                MSE = sphere + cylinder/2

                J0 = −(cylinder/2) × cos (2 x axis)

                J45 = −(cylinder/2) × sin (2 x axis)

Visual Acuity Measurement

Binocular corrected distance visual acuity (BCDVA) was immediately measured after finishing each objective refraction. BCDVA was assessed through the oculars of the Eye Refract, in the case of the objective refraction with this system, and with trial frame, in the case of the objective refraction with the VX110. The high-contrast (100%) ETDRS chart of the digital screen set at 4 meters of distance was used to measure the BCDVA.

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Sarah Jhonson
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International Journal of Case Reports
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