Hyperacuity perimetry. Assessment of macular function through ocular opacities.

"Hyperacuity perimetry" provides localized measures of visual performance across the central visual field that are resistant to the retinal image degradation caused by media opacities. A normal observer, viewing a vernier stimulus through an artificial opacity (ground glass), exhibits a pronounced performance improvement with foveal viewing, relative to viewing at visual field points just 2 degrees to 4 degrees parafoveal. Patients with central lesions exhibit anomalous hyperacuity perimetric profiles, even in the presence of a simulated ocular opacity. We conclude that in patients with media opacities, hyperacuity perimetry can preoperatively evaluate the distribution and size of areas of visual loss across the central visual field and the stability and location of primary fixation. This potentially powerful test of macular function behind media opacities is as easy to apply as any static visual field measurement.