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Neeraj Kumar, Alex D. Hwang, Eliezer Peli; Characterizing AMD field loss for contact lens simulating scotomas. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5184.
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© ARVO (1962-2015); The Authors (2016-present)
While controversial for a long time it is now clear that central scotoma can be simulated with tinted contact lenses as long as the pupil is kept mitotic. To use this tool in studies, it is important to determine the characteristics of the scotomas. In retrospective, observational study computationally we examined the shapes, dimensions, locations of patients’ scotomas, and the direction and distance of preferred retinal loci (PRL) with respect to the fovea.
Computerized central field perimetry records of 161 eyes of 87 AMD patients collected in prior studies were retrieved. An analytic tool was developed to computationally quantify the scotoma’s size expressed as the angular diameter of equivalent area circle (DEAC), width, height, location and direction of the scotoma with respect to the PRL, and distance of the PRL with respect to the fovea. The direction of the scotoma (e.g. superior, inferior, left, right, etc.) was quantized using the location of the center of gravity of the scotoma relative to the PRL position. The position of the fovea was estimated using the optic nerve head scotoma and assuming that the location for the optic nerve head scotoma was centered at ±15°, -2°.
Out of 161 eyes, central scotoma was present in 95 eyes. The optic nerve was marked in 74% (n=64) in OD and 79% (n=69) in OS. The most common direction of the scotoma relative to PRL was to the right (36%), followed by left (28%), and superior-right (11%). The mean (SD) size of the scotoma in DEAC was 9.6° (6.1°). The mean (SD) width and height of the scotoma were 11.3° (7.6°), and 11.0° (6.6°), respectively. A statistically significant difference between OD and OS was found in the scotoma size in DEAC (t(159) = -4.4, p<.001), width (t(159) = -5.3, p<.001), and height (t(159) = -4.6, p<.001). The median (IQR) distance of the PRL from fovea was 4.17° (1.9-10.55)°, where it varied for each PRL direction, 3.4° (1.9-6.3)°, 3 (1.5-7.3)°, and 15.11° (11.6-24.6)° for right, left, and superior-right, respectively.
The scotoma was mostly in the right and left octant to the PRL, and the PRL is about 3° from the fovea for these directions. Since the PRL characteristics differ between OD and OS, only one eye’s PRL should be used for binocular viewing simulation. The mean/median and range data will be provided to serve as guidelines for scotoma simulation experiments with contact lenses in various functional performance studies.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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