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Esther G Gonzalez, Luminita Tarita-Nistor, Moshe Eizenman, Mark Mandelcorn, Martin J Steinbach; Preferred retinal loci during binocular viewing at two viewing distances. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):547.
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© ARVO (1962-2015); The Authors (2016-present)
To determine, in patients with AMD, whether the absolute location of monocular and binocular PRLs changes as function of viewing distance. The method presented here uses a remote eye-tracking system that measures the optical axes of both eyes without user calibration. This method yields the absolute location of monocular and binocular PRLs which, until now, could only be done monocularly.<br /> We hypothesized that the locations of the binocular PRLs would not change as a function of viewing distance.
Fifteen eyes from 8 patients with AMD fixated a 3 deg cross for 15sec. The PRL location for the patients was recorded monocularly with both the MP-1 microperimeter and the eye-tracking system and then binocularly with the eye-tracking system. The eye-tracker measured the horizontal and vertical components of angle Kappa, which is the angle between the optical and the visual axis (PRL for patients, fovea for controls) in each eye. Using the values of 10 control eyes, a transformation from the eye-tracking to the MP-1 coordinate systems was created to predict the absolute location of the monocular and binocular PRLs in patients. Measurements were made at two viewing distances: 70 cm and 6m.
For the patients, the mean prediction errors for the monocular PRLs (MP-1 - eye-tracker system) ranged from 0.03 to 1.05 deg. Viewing distance did not affect PRL location during binocular viewing. For the 7 patients with complete data for the two eyes, there were no consistent changes in PRL when viewing changed from monocular to binocular as a function of viewing distance: 3 patients showed no appreciable changes in PRLs, 2 patients showed larger changes at 70cm than at 6m and 2 patients showed the reverse. For all patients, the PRLs of the better eye changed less than the PRLs of the worse eye.
Binocular PRL location did not change as a function of viewing distance. Changes in PRL location from monocular to binocular viewing depended on the characteristics of the patients’ scotomas and not on the viewing distance. The absolute location of the PRLs (i.e., relative to the optic disk) can be predicted with acceptable accuracy with the method presented here.
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