Lens rim artifact in automated threshold perimetry.

In central static threshold visual fields (Humphrey 30-2 Program) performed with a corrective lens, lens rim artifact (LRA) was present in 10.4% of 704 fields examined retrospectively and 6.2% of 276 fields evaluated prospectively. Lens rim artifact most commonly presented as a combination of absolute and relative defects involving the temporal quadrant either alone or in combination with another quadrant. Lens rim artifact was related to seven different types of interpretational errors, five of which led to an overdiagnosis and two to an underdiagnosis. Risk factors for the occurrence of LRA include older age, high hyperopic correction, and location specific involvement probably due to a limitation in perimeter design. Field defects involving only the four targets at 27 degrees eccentricity in the temporal quadrant were due only to LRA in this series and may be disregarded when interpreting the Humphrey 30-2 Program. Recommendations are made toward minimizing the occurrence of LRA and avoiding interpretational errors associated with LRA.