Electroretinograms of a normal individual and patients with forms of stationary night blindness. The tracings in the top row are the responses to single flashes (repeated every 2 seconds, or 0.5 Hz) of blue light that is so dim that only rods are stimulated. The middle row shows the responses to 0.5-Hz, bright, white flashes that stimulate both rods and cones. The bottom row shows the responses to bright, white light flashing 30 times per second (30 Hz); cones but not rods elicit individual responses to light flashing at this frequency. Thus, going from the top to bottom rows, one observes normal rod-isolated responses, combined rod-plus-cone responses, and cone-isolated responses. The time of the light flashes is denoted by the vertical dashed line in the top and middle rows and by the solid vertical lines within the tracings of the bottom row. The letters “a” and “b” in the normal rod-plus-cone electroretinogram (left column, middle row) label the a-wave and b-wave, respectively. The arrows in the tracings of the bottom row denote the cone peak implicit times (that is, the time interval between a light flash and the corresponding peak amplitude). In all tracings, two or three consecutive sweeps are superimposed. The calibration symbol in the lower right corner designates 50 ms horizontally and 100 μV vertically. The column headings refer to the genetic defect causing each patient’s night blindness. Note that the patients with rhodopsin, transducin, and rhodopsin kinase mutations have no observable rod b-waves with these test conditions, whereas the patient with a defective 11-cis RDH (fundus albipunctatus) has a subnormal rod b-wave that becomes normal in amplitude after 5 hours of dark adaptation. Mixed rod-plus-cone responses to 0.5-Hz flashes of bright white light (middle row) are without a prominent cornea-positive b-wave (rhodopsin and rhodopsin kinase cases) or have subnormal b-waves (transducin) except for fundus albipunctatus where the rod-plus-cone b-wave is normal. The rod-plus-cone electroretinograms in fundus albipunctatus would be subnormal after 45 minutes of dark adaptation if the dark-adaptation period had been preceded by exposure to intensely bright light that would bleach a large proportion of the patient’s rhodopsin. In all of these forms of stationary night blindness, cone electroretinograms in response to 30-Hz white flickering light are normal or near-normal in amplitude and have normal peak implicit times (that is, 32 ms or less). | Dryja, T. P. (2000). Molecular genetics of Oguchi disease, fundus albipunctatus, and other forms of stationary night blindness: LVII Edward Jackson Memorial Lecture. American Journal of Ophthalmology, 130(5), 547–563.

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