Enhanced S-cone syndrome (ESCS) is an unusual disease of photoreceptors that includes night blindness (suggestive of rod dysfunction), an abnormal electroretinogram (ERG) with a waveform that is nearly identical under both light and dark adaptation, and an increased sensitivity of the ERG to short-wavelength light [1,2]. The disease is caused by mutations in the orphan nuclear receptor transcription factor NR2E3 (also known as photoreceptor nuclear receptor), which is expressed exclusively in rods [3,4]. Recent human genetic studies have also demonstrated mutations in this gene in Goldmann-Favre syndrome and many cases of clumped pigmentary retinal degeneration [5].