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Sally Chang, Donald C. Fletcher, Ronald A. Schuchard, Manfred MacKeben; Macular Scotoma Topography in Dynamic Visual Field Testing. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4365.
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To assess if topographical changes in retinal function as measured by scanning laser ophthalmoscopy (SLO) are associated with difficulty performing search and identify tasks using dynamic visual field (DVF) testing.
14 patients with macular pathology referred for low vision rehabilitation had 1 meter ETDRS visual acuity, Rodenstock SLO macular perimetry and DVF testing performed in their initial evaluation. The DVF test consisted of a suprathreshold Landolt C stimulus presented randomly on a computer monitor along 8 vectors from a central reference point at 2, 4, 6 and 8 degrees of eccentricity. The patients were encouraged to not fixate on the central reference point which disappeared as the stimulus was presented, but actively look for the stimulus. The time from presentation to when the stimulus gap was correctly identified was recorded as the DVF response times.
Patient age median (range) was 85 (61-90) years with 50% female. Visual acuity mean (range) was 20/133 (20/80-20/366). All patients had an SLO demonstrated dense scotoma that corresponded to at least one vector on the DVF test based on the scotoma position relative to the preferred retinal locus (PRL). A total of 47% of DVF vectors tested had a corresponding SLO dense scotoma. There was considerable variation in response time from patient to patient but within each patient, the scotoma vectors had slower response times than scotoma free vectors. Mean DVF response latency was 14.5 seconds for scotoma vectors and 9.5 seconds for scotoma free vectors (p<0.05). Age and visual acuity showed no significant relationships to DVF response times.
The DVF test has already been shown to have a higher correlation with reading performance than visual acuity. Presence of a macular scotoma near the preferred retinal locus also appears to slow the process of search and identification. The demonstration of topographical correspondence lends support to the concept that scotoma awareness and compensatory eye movements are important in low vision rehabilitation. This inexpensive and easily administered test may have clinical value where macular scotomas are causing reading, page navigation as well as other ADL challenges that involve visual search. The DVF test may be useful as a training tool and also to monitor and evaluate rehabilitation outcomes.
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