What Are the Causes of a Feline's Dilated Pupils?

Cats are complex animals that use both body language and vocalizations to communicate with people. One way they communicate is through the use of their eyes. A cat's pupils can convey messages to other animals and people. However, a cat's dilated pupils can be indicative of a number of things, other than adjusting to the amount of light. Such things include mood and medical conditions, including hypertension, diabetes and glaucoma.

  1. Mood

    • Dilated pupils in a cat can indicate their mood. When a cat is fearful or aggressively excited, its pupils will dilate. Additionally, your cat's eyes may also dilate as a way to express its excitement over seeing you, a fellow feline or when it's time to be fed. For example, the more fear a cat feels, the wider and more dilated its eyes will be. Fear can quickly turn into aggression in a cat. The cat's pupils will be more dilated and, coupled with its ears being turned back, is indicative of a warning to the other person or animal.

    Hypertension

    • Hypertension, or high blood pressure, in cats commonly results from other medical problems such as kidney disease. High blood pressure in cats can cause the eyes to swell and bleed, often resulting in blindness. Retinal detachment, caused by major head trauma, can also occur, causing blindness. Most times, a cat will be asymptomatic (no symptoms). However, when signs and symptoms do appear, a cat may have visual impairment, lethargy, depression and seizures.

    Diabetes

    • Diabetes is a disorder that primarily affects how glucose (blood sugar) in processed in the body. The pancreas manufactures insulin -- a hormone that signals the body's cells to take in the glucose. If there isn't enough insulin, the glucose levels in the blood rise and therefore, the glucose isn't able to be used by the cells for energy. Other organs, such as the kidneys, in the cat may attempt to compensate for this problem by getting rid of the glucose surplus in the blood by using copious amounts of water. Treatment includes a proper diet for the cat, or medications, if needed.

    Glaucoma

    • Glaucoma is an increasing pressure in the eye caused by a buildup of the clear fluid in the eye that doesn't properly drain. The fluid, called aqueous humor, usually drains through a special sieve-like area, but in glaucoma, the delicate balance of fluid and drainage is interrupted when the drain becomes clogged. In cats, glaucoma can be classified as primary or secondary. Primary glaucoma (an inherited condition) is rare in felines but secondary glaucoma occurs when other eye problems cause improper fluid drainage. Glaucoma in felines is commonly caused by chronic uveitis (an inflammation inside the eye).