Ocular fundus, chromatic pupillary light reflexes, and electroretinogram of a day-blind MAS. A. Compiled image of the normal ocular fundus of the day-blind MAS. B. Chromatic pupillary light reflexes. i. Day-blind MAS: Normal pupillary constriction was observed with the blue light stimulus (480 nm, 200 kcd/m2), whereas no pupil constriction was observed with the red light stimulus (630 nm, 200 kcd/m2) of the same light intensity. ii. Normal canine: Complete pupillary constrictions were elicited with both bright red and blue light. C. Electroretinograms. Compared to a normal, age-matched, mixed-bred colony dog (ii) with normal cone-mediated ERG responses (ii, black arrows), the recordings of the day-blind MAS (i) revealed normal rod- but absent cone-mediated retinal function.