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Mateusz Tomasz Jaskulski, Norberto Lopez-Gil, Andrei Martinez-Finkelshtein, Vicente Fernández-Sánchez; Objective Amplitude of Accommodation and Refraction Using a New Wavefront Metric Dependent on Pupil Radius. Invest. Ophthalmol. Vis. Sci. 2017;58(8):322.
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© ARVO (1962-2015); The Authors (2016-present)
To obtain fast and accurate measurements of the equivalent sphere (M) and amplitude of accommodation (AA; subjective SAA, objective OAA), taking into account the potential changes in refraction due to the changes of pupil size.
An empirical wavefront refraction metric (MTR) was formulated using objective (OR) and subjective refraction (SR) measurements, compiled from 3 datasets: Murcia (174 eyes), Houston (40), and Alabama (94). It was tested using an independent dataset, Indiana (200 fully corrected eyes). OR were calculated for all eyes, for pupil radii (rescaled) from 1.00 to 3.75mm. The results were compared with ones obtained with traditional metrics; Paraxial and minRMS. The MTR metric was then used to compute the OAA in 140 eyes (ages 17-55), for which OR measurements spanning the full range of accommodation had been obtained using the irx3 aberrometer (Imagine Eyes, France), in 0.5D steps of stimulus vergence. OAA was calculated as the maximum minus minimum value of OR. The results were compared to SAA, obtained with minus lenses, and custom Badal optometer.
The MTR metric predicted the subjective M with a mean, inter-subject error ≤0.12D for all pupil radii, both in the 3 datasets used to formulate it (308 eyes), and the independent dataset, Indiana (200 eyes). Equivalent sphere values calculated by the MTR metric lie between these of the minRMS and Paraxial metrics (Fig. 1), which for large pupils usually give values too myopic or too hyperopic, respectively.The OAA estimated by the MTR metric was on average 0.91±0.10D smaller than SAA obtained with the Badal method, and 0.75±0.09D smaller for the minus lenses method.
The new MTR metric gives accurate prediction of the subjective M for the whole range of pupil radii, even though the SR may change due to spherical aberration (SA) for large pupils. On average, it was found to underestimate the SAA by 0.85±0.10D, which is expected, as the effects of the depth of field, present in subjective measurements, are not taken into account in objective measurements of far, and especially near points (see Bernal et al. OVS, 2014).The new metric can be used to estimate OR and OAA for pupil radii different than the measurement radius, and of interest to studies of children, and low illumination, where the pupil radius and SA can be large.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Subjective - Objective Refraction Error in Function of Pupil Radius
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