Repeatability of measurements with a double-pass system

Abstract

No author has a financial or proprietary interest in any material or method mentioned.

Binocular summation and visual function with induced anisocoria and monovision

“…Tarrasa, Spain), an optical instrument based on the double-pass technique widely validated [27][28][29]. This device provides information on higher-order aberrations, diffraction, and scattered light, using an infrared laser diode (λ = 780nm) as light source.…”

“…A lower value indicates lower retinalimage quality due to a greater influence of ocular aberrations and scattered light. On the other hand, the MTF represents the loss of contrast produced by the eye's optics on a sinusoidal grating as a function of its spatial frequency [29]. The MTF cutoff theoretically represents the spatial frequency, in cycles per degree (cpd), corresponding to an MTF value of 0.…”

“…However, due to the noise introduced by the CCD camera, which collect the double-pass image, the MTF cutoff is the frequency (cpd) at 1% of maximum MTF. That is, the double-pass device uses a MTF threshold value of 0.01 for reporting the MTF cutoff [27,29]. The definition used here for this parameter is not equal to the classical definition, which is calculated based on wavelength and pupil diameter [30].…”

Optics of Astigmatism and Retinal Image Quality

“…Figure 13 shows the double-pass images and the corresponding intensity profiles as a function of the angle (averaged section of the double-pass image), MTFs, and simulated vision using a standard visual acuity chart for an emmetropic eye, an eye with uncorrected astigmatism and an eye with spherical ametropia. The measurements were taken with the Optical Quality Analysis System (OQAS, Visiometrics, S.L., Spain) (Güell et al, 2006;Saad et al, 2010;Vilaseca et al, 2010a), which is a double-pass system currently available for use in daily clinical practice that includes this application. The double-pass technique has been used extensively to determine the optical quality of the eye, mainly by means of the ocular MTF.…”

Discrimination between Surgical and Nonsurgical Nuclear Cataracts Based on ROC Analysis

“…From this technique an objective scattering index (OSI) proposed by Artal et al (15) can be computed. This parameter takes into account the forward-scattered light and has been validated in several studies (16) (17) (18). Other studies have suggested the usefulness of this parameter in the clinical prediction of intraocular scattering (16) (19) (20) and it has been shown to be useful for grading nuclear, cortical and posterior subcapsular cataracts (15)(21).…”