How is CSNB diagnosed?
It is extremely difficult to measure quality of vision in animals as they cannot communicate with us. However, we can objectively measure the function of their retina. The most objective way we have of testing retina function is the electroretinogram (ERG). This is a test that measures the retinal cell’s electrical activity in response to light stimuli. We can accurately assess the ability of the retina to responds in dark conditions as well as bright light conditions, by varying the conditions and the stimuli used while doing the test. Normal ERG parameters are established through testing hundreds of horses under different test conditions. Horses with reduced retinal function will have changes in the ERG recordings that can be quantified. Normally, when a human or animal is put in a dark room vision is initially very poor until the retina begins to adapt. This is called dark adaptation; the retina actually becomes more sensitive to light as the person or animal is left in the dark. Ho
