Enhanced S Cone Syndrome: Testing An Explanation for Hypersensitivity of the S Cone System

Abstract

Enhanced S cone syndrome (ESCS) is a retinal degenerative disease associated with nightblindness and hypersensitivity of the short-wavelength-sensitive (S) cone system.1-3 Patients with ESCS have characteristic electroretinograms (ERG) with a large negative component (a-wave) in the presence of a background field. The a-wave can be as large or larger than the normal dark-adapted rod a-wave.1-7 Recent studies have demonstrated that these a-wave responses are mediated almost entirely by receptors with S-cone pigment.1-3,8,9 The syndrome gets its name from these large a-wave responses and psychophysical evidence of hypersensitivity of the S-cone system.2