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D. P. Greene, S. K. Houston, III, S. A. Newman; Rarebit Perimetry: Number of Test Passes Needed to Identify Visual Field Defects. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2338.
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Rarebit perimetry has been demonstrated to effectively detect a wide range of visual field defects. The current protocol includes 5 test passes for data collection. In a recent study we demonstrated the usefulness of Rarebit to detect visual field defects in hospitalized patients. Since attention span is limited we were interested in whether the test could be shortened in duration without losing the ability to recognize pattern defects.
10 individuals with distinct visual field abnormalities (initially detected by standard automated perimetry) underwent Rarebit testing on each eye utilizing the protocol described by author Lars Frisen, first completing 5 passes followed by 2 passes. A neuro-ophthalmologist blinded to the patient data verbally described the defect pattern of visual fields from each patient, randomly selected as either 5-pass or 2-pass fields, and then attempted to match these fields with their correlates (e.g. 5-pass with 2-pass fields) based on pattern recognition and verbal description. In addition, mean test time (MTT) for each eye was compared between the 5-pass and 2-pass tests.
10 patients (3 men, 7 woman) ages 38-88 (average 60.6, SD ± 15.0) participated. In the matching exercise, each field was successfully paired with its correlate, and verbal descriptions of correlate fields were consistent. MTT for each eye was 6.95 min (SD ± 0.71 min) on 5-pass tests and 2.37 min (SD ± 0.29 min) on 2-pass tests.
Rarebit perimetry can reliably demonstrate visual field defects when performed using 2 passes. Additionally, 2-pass testing is 65.9% shorter in duration compared to 5-pass testing and is completed in approximately 7 minutes for both eyes, including time allowed for patient instruction. A visual field test that minimizes testing time while maintaining reliable detection of defects may benefit patients that are unable to complete time-intensive exams.
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