Figure 1.

Electroretinograms of normal and affected dogs. Electroretinograms (ERGs) from a 7 weeks old normal dog (A), a 12 weeks old dog affected with canine cone-rod dystrophy 3 (crd3; B), a crd3-affected dog aged 1.2 years (C), a 2 years old crd3-affected dog (D), and a 4.9 years old crd3-affected dog (E). Each vertical panel presents electroretinogram (ERG) responses to a red flash, a blue flash, a white flash, 5 Hz low-intensity white flashes (Rod), and 30 Hz high-intensity white light flicker (Cone). Short vertical arrows under the Rod and Cone flicker responses indicate the onset of the flickering light stimuli. Red and White traces represent mixed rod-cone responses, Blue and Rod traces are rod-specific, and Cone traces are cone-specific. Responses of the 12-weeks-old crd3-affected dog appear normal (B), but by 15 months of age, cone dysfunction is detected as reduced 30 Hz flicker responses (C), and is followed at later ages by continued deterioration of both cone and rod responses (D, E). At all ages, the loss of cone function is more prominent than that of rods. Vertical calibration bar=100 µV; horizontal=200 ms for rod flicker; and other responses are 100 ms.