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JL Keltner, CA Johnson, KE Cello, MA Kass, MO Gordon, SE BandermannOcular Hypertension Treatment Study Group; The Characterization and Comparison of OHTS Abnormal Visual Field Classifications using the 24-2 vs. the 30-2 Testing Strategies . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2151.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: A classification system was developed for the Ocular Hypertension Treatment Study (OHTS) to describe visual field (VF) abnormalities. Methods: Three certified readers classified 500 OHTS abnormal VFs (1000 hemifields) using 17 abnormality classifications. To simulate a 24-2 visual field, a template was used on the 30-2 probability plots to occlude the outermost ring of points except for the two points straddling the horizontal meridian on the nasal side. Readers assigned separate classifications to the upper and lower hemifields using the Total and Pattern Deviation probability plots as the primary basis for the classifications. If 2 out of 3 readers agreed, then a final abnormality classification was determined for that hemifield. If 2 readers did not agree, then the VFs were adjudicated by group consensus. After a final classification was made for each hemifield, the 30-2 abnormality classifications were compared with the 24-2 abnormality classifications and the frequency and location of differences were determined. Results: Of the 1000 hemifields, 671 (67%) had the same type and location of abnormality using both testing strategies and 329 (33%) had either a different type/location of abnormality or were classified as normal using the 24-2 strategy. 181/329 (55%) had a different type/location of abnormality using the 24-2 strategy and 148/329 (45%) were classified as normal using the 24-2 strategy. 127/148 (86%) classified as normal using the 24-2 strategy, were classified as peripheral defects using the 30-2 strategy. Peripheral defects included the following: temporal wedge (38), inferior depression (29), partial peripheral rim (26), superior depression (25), and nasal step (9). Conclusion: The 24-2 testing strategy may reduce artifactual defects which are evident by the 33% of abnormal hemifields that either had a different type/location of abnormality (18%) or returned to normal (15%). It is uncertain how many early glaucomatous defects might be missed as seen with temporal wedge defects 26% (38/148) and nasal step defects 6% (9/148) classified as normal using the 24-2 testing strategy.
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