Central field perimetry of discriminated targets: I. Results for normal individuals using high-contrast targets

Abstract

Purpose: A new perimetry method is described to evaluate central vision under multiple hue, illumination, and contrast conditions; results are described for normal individuals using high-contrast targets.

Methods: For 70 normal eyes of individuals with varying age, the ETDRS chart acuity was determined as well as discriminated target perimetry using high-contrast targets presented for 250 ms at locations up to 10 degrees eccentricity. Retesting was performed to evaluate for learning and repeatability for the thresholded acuity at each eccentricity.

Results: The ETDRS acuity averaged 1.15+/-0.37 arc min minimum angle of resolution (MAR) with best correction (20/23 equivalence). At fixation, the thresholded acuity for high-contrast targets paralleled the ETDRS acuity and averaged 1.75+/-0.85 arc min MAR (20/35 equivalence), and declined with increasing eccentricity in a linear fashion to 5.81+/-3.97 arc min (20/116 equivalent) at 10 degrees eccentricity. Linear regression showed Vmar=1.74+0.330 (*) eccentricity in degrees (R (2)=0.966, P<0.0001). Testing time required approximately 8-10 min per eye. Repeated testing showed only minimal learning experience at the most peripheral locations. The test-retest 95% confidence limits of difference measured 1.12 arc mins MAR at fixation (64% of the mean) and remained approximately the same proportion to the mean thresholded acuity outwards to 10 degrees eccentricity.

Conclusion: The methodology seems rapid and reliable for measuring discriminatory visual function of optotype targets throughout the central 20 degrees diameter visual field.