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A.J. Anderson, C.A. Johnson; Does a Criterion of Normal Perimetric Performance Generate a Supra-normal Sub-population? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):68.
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Purpose: To interpret the results from automated perimeters, a normative database must be developed to which individual results may be compared. Typically, a set of criteria is used to determine what subjects may be included in the database. We wished to determine whether a criterion of normal performance on an established clinical perimeter generated a sub-group with supra-normal perimetric performance. Methods: The perimetric performance of a group of one hundred subjects, aged 20 to 85 years, was analysed retrospectively. Results for right eyes were examined only. Subjects had visual acuities better than 20/40, no history of eye disease, and normal slit lamp biomicroscopic and ophthalmoscopic examinations. Subjects performed test/retest visual field examinations on the Humphrey Field Analyser (HFA) 24-2 test, and on a custom frequency-doubling (FD) perimeter with 4 degree targets spaced in the same 24-2 pattern. Testing was performed over four visits. Results: Test-retest correlation (r-squared) for mean defect (MD) and pattern standard deviation (PSD) indices were 0.43 and 0.17 for the HFA, and 0.71 and 0.23 for the FD perimeter. Three subjects with HFA MDs in the lower 5% on initial testing gave similarly low MDs upon retest, whereas no subject was common between the test and retest lower 5% for HFA PSD. Correlation between the HFA and FD test results were 0.17 (MD) and 0.00 (PSD). Only one subject was in the lower 5% of initial test MDs for both HFA and FD testing, with no subjects common between the lower 5% for PSD. Conclusions: Although a criterion of a normal MD may produce a sub-population with supra-normal perimetric performance, a criterion of a normal PSD is less likely to. The poor correlation between indices from different types of perimetric tests (achromatic versus frequency doubling) in disease-free subjects suggests that a normal criterion on one test is unlikely to result in a supra-normal sub-population on another.
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