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Chris A Johnson, Michael Wall, Lars Frisén, Tana Wagschal; Development and Reliability of the Tangent Corner Test (TCT) Visual Field Evaluation. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5977.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a procedure for measuring the extent of the visual field along the horizontal meridian to screenfor vigabatrin (Sabril) toxicity that could cause peripheral visual field constriction, and to assess the test-retestreliability.
The Tangent Corner Test (TCT) measures the temporal extent of the visual field along the horizontalmeridian. The patient sits 1 meter from the corner of a strip of paper mounted at eye level along the two intersecting walls (left figure), with large markings for each 5 degree eccentricity out to 110 degrees and small markings for each degree. The right figure demonstrates the visual field measurement process. A mirror at the center is used as a fixation stimulus, and allows the examiner to view the patient’s eye and head alignment during the testing of each eye separately. A translucent eye patch occluded the non-tested eye. Illumination of the TCT was between 10 and 30 candelas per meter squared, and a tennis ball painted black and mounted on a dowel rod was used as a high contrast peripheral vision stimulus. Five measurements were obtained, with the stimulus moving from the periphery at a rate of 2-3 degrees per second. A total of 76 patients with complex partial seizures were tested on three separate occasions, as part of a clinical trial sponsored by Lundbeck.
The average location where the peripheral stimulus was detected was beyond 90 degrees, with averagevalues between 94 and 96 degrees. The standard deviation of the five measures was about 2 degrees, and the coefficient of variation (COV) was approximately 2%. The results below present average results for the right and left eyes for the three testing sessions. Results from two other visual field tests (Humphrey Field Analyzer 30-2 SITA. Standard or SITA Fast, and threshold determinations at every ten degrees from 40 to 70 degrees eccentricity along the nasal and temporal horizontal meridian) were more variable than the TCT in this population. (Right eye 95-96 deg, SD= 1.6-1.9 deg, COV= 1.80 - 2.15%, Left eye 94-95 deg, SD= 1.8-1.9 deg, COV = 1.8 - 2.0%).
The Tangent Corner Test (TCT) provides a reliable determination of horizontal visual field extent, even inpatients with complex partial seizures who may have cognitive impairment and attention deficits.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Schematic representation of the Tangent Corner Test (TCT) in the left panel, and a demonstration of the test procedure in the right panel.
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