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Luminita Tarita-Nistor, Esther G Gonzalez, Moshe Eizenman, Natalie Landon-Brace, Samuel N Markowitz, Martin J Steinbach; Identification of Preferred Retinal Loci during Binocular Viewing in Patients with Central Vision Loss. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4136.
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Until now, the absolute location of the PRL of patients with central vision loss could only be identified monocularly. We tested a new method to measure/predict the location of the PRL in each eye in patients with central vision loss when viewing binocularly. The method uses a unique remote eye-tracking system that estimates the optical axes of both eyes without user calibration. We hypothesized that this method predicts the locations of monocular and binocular PRLs accurately.
Five experienced controls and 6 patients with stable central vision loss were tested. Their fixation was recorded monocularly with both the MP-1 microperimeter and the eye-tracking system and binocularly with the eye-tracking system. The eye-tracker measured the direction of the optical axis and the angle between the PRL (fovea for control subjects) and the optical axis in each eye. The MP-1 measured the location of the PRL relative to the optic disk; that is, its absolute location. Using the monocular measurements of the eye-tracker and the MP-1, in control subjects, a transformation from eye-tracking measurements to MP-1 measurements was created and used to predict the absolute location of the PRLs in patients. The predicted values for monocular viewing for each eye were compared with the measured MP-1 values.
The prediction errors of the horizontal and vertical coordinates were -0.1 ± 0.7 deg and -0.1 ± 1.1 deg for the right eye, and -0.1 ± 0.9 deg and 0.0 ± 1.0 deg for the left eye. The same transformation was then used with measurements of the eye-tracker’s PRLs under binocular viewing, to obtain the absolute locations of the PRLs in the MP-1 coordinate system.
By transforming the measurements of the PRL location from an eye tracking coordinate system to the MP-1 coordinate system, the absolute location of the PRLs (i.e., relative to the optic disk) during binocular viewing can be predicted with an acceptable accuracy.
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