A special tube called the nasolacrimal duct permits tears to drain from the eye into the nose. Tearsare made of water, oil, and mucus produced by the lacrimal glands, glands in the third eyelid, mucus glands, and meibomian glands. Additionally, it helps keep the eye moist with tear production.Įyes require moisture which comes from tears produced by several glands located around the eye. The third eyelid extends over the eye to protect it from scratches (like when running through a bush or brush) or is often seen in sick dogs and cats in response to illness or inflammation. Usually not noticeable, the third eyelid is located in the inside corner of the eye (closest to the nose) and is usually whitish-pink in color. Blinking keeps the eye moist by spreading tears over the surface of the eye and clearing away small pieces of dirt and dust.Ĭats and dogs get additional eye protection from the third eyelid or nictitating membrane. Together, this bundle of nerve fibers forms the optic nerve which transmits the image seen by the eye to the brain.ĭogs and cats have both upper and lower eyelids that blink reflexively, protecting the eye. The most sensitive part of the retina, called the area centralis, holds thousands of photoreceptors, each attached to a nerve fiber. Fun Fact: Road engineers mimic this effect for highway reflective markings on roads and signs, making it easier to see by motorists at night or in dim lighting! This reflective layer of the retina in the eye is called the tapetum lucidum, a layer that humans do not have.

You may be familiar with the blue or greenish reflection of a cat’s eyes when shining a flashlight or caught by a car’s headlights. While they can’t see if it’s totally dark, their vision is dramatically better than ours because their specialized eye functions allow them to see even when there is very little light. Rumor has it that cats can see in the dark. Cats have many rods which give them 6 times better vision in dim light than people. Of the 2 types of photoreceptors called cones and rods, conesgive cats an increased ability to hunt with more accurate and binocular vision. The area called the retina has light-sensing cells called photoreceptors. The pupil is the black area in the center of the eye controlled by a circular muscle that becomes smaller in bright light to allow in less light, and larger in decreased light to allow in more light.īehind the iris is the lens which works to bring objects into focus. The iris is the rounded, colored part of the eye that works to make the pupil smaller or larger, adjusting the amount of light entering the eye. The cornea is the clear rounded part on the front surface of the eye which functions as protection and allows light in to focus onto the retinaat the back of the eye. The sclera is the white area of the eye covered by the conjunctiva which extends to the edge of the cornea covering the inside of the eyelid. The orbit is the bony cavity or socket which holds the eyeball as well as muscles, nerves, blood vessels, and structures that produce and drain tears. The anatomy of dogs’ and cat’s eyes work by adjusting to different light conditions essential for hunting or tracking prey. This constantly produces images that are rapidly sent to the brain to be processed. Eyes work by adjusting to different light conditions, focusing on objects near, far, and in between.

Dog unequal pupil size