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.
1 Fainting/Collapsing: If your dog faints or collapses at any time, seek veterinary help. It may be a sign of many different serious illnesses, heart disease being one of them. 2  Weakness: Weakness may be seen as a general sign of aging, but be sure to seek veterinary attention if it is combined with other symptoms.