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Emily K Wiecek, Mary Lou Jackson, Peter J. Bex; Binocular Microperimetry with Simulated Asymmetric Bilateral Scotomas. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):549.
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© ARVO (1962-2015); The Authors (2016-present)
It is difficult to perform visual field testing on patients with central field loss (CFL) because they may fixate with a Preferred Retinal Location (PRL) in an unknown location outside the former fovea. Microperimeters combine simultaneous imaging and testing to measure the PRL location and CFL in retinal coordinates, but are expensive and limited to monocular measurement. We develop and evaluate a binocular microperimetry system that uses eye tracking to track the optic nerve head (ONH) and stereo shutter glasses that support simultaneous and independent presentation of stimuli to each eye.
PRL location, and monocular and binocular microperimetry were assessed in 6 normally sighted participants with and without independent binocular simulated scotomas. The simulated scotoma was presented as a 3° or 6° circular patch of pink noise in a raised cosine window (λ=0.5°) to each eye monocularly and required the participant to use a PRL to fixate a central cross. To determine the location of the PRL and map stimulus presentation in retinal coordinates, the ONH was mapped in each eye with kinetic perimetry. The ONH location in each eye was compared with fundus images offline and provided retinotopic references for monocular and binocular microperimetry with Goldman III targets presented in a polar 3-21 pattern.
The ONH location in our system corresponded to its location in fundus images and was an average location of 15.5° temporal and 2° superior to fovea, across observers. The ONH location mapped with asymmetric, binocularly-simulated scotomas shifted vertically from the central cross an average of 6° (the size of the larger scotoma) consistent with the use of a PRL in upper visual field. The ONH location measured with a monocular scotoma, however, corresponded to a shift the size of the independent monocular scotoma, highlighting a difference in monocular and binocular assessment of PRL location. Both binocular and monocular perimetry accurately mapped the location and extent of the simulated scotoma in all six participants after accounting for eye movements with eye tracking data.<br />
A computer-based binocular microperimetry system can offer binocular assessment of CFL induced with simulated gaze-contingent scotomas. This system can provide reliable information about the binocular nature of visual field loss, fixation stability, and PRL location in CFL patients.
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