Best Answer: The pupil size limits the the amount of light that enters the eye. There are also day-time photoreceptors, the cones, which occur with three kinds of photo-sensitive pigments, for red, yellow-green, and blue.
Those âdevotedâ dogs lying on their mastersâ graves? Theyâre depressed. âMany dogs are simply depressed for their whole lives because theyâre deprived of the normal amount of attention, exercise, and stimulation they need from day one. These humans wonât know they have a problem and wonât want the dog any livelier as that wouldnât fit in with their lifestyle,â says Tamara.
Causes of Collapsing in Dogs. Examples of illnesses that may cause canine collapse include: Heart disease. This includes congenital heart disease (birth defects in the heart), acquired valvular heart disease (leaky heart valves), heartworm disease, tumors of the heart, pericardial disease (disease of the lining of the heart) and primary cardiac arrhythmias (erratic heart beat).