Cat Eyes: Adaptations for Night Vision & Functionality

What are a cat's eyes?

Cats possess a unique visual receptor known as their eyes.

Where are a cat's eyes located?

Cats have two eyes, each situated on either side of their face. There is considerable variation among animal species in terms of the position, size (including the bony socket), and the size and shape of the eyelid slit (the opening between the eyelids). Within the feline species, these structures are quite consistent, although certain breeds, such as Persians and Burmese cats, may appear to have eyes that protrude more from the skull and seem to have wider slit openings.

What is the general structure of a cat's eyes?

Cats' eyes are composed of three concentric layers or tissues: the outer fibrous coat, the middle vascular coat, and the inner neural coat. The fibrous coat is the outermost layer of the eye, consisting of the sclera (the white part of the eye) and the cornea (the transparent covering over the eye's front). The vascular coat is the thicker middle layer, commonly referred to as the choroid. It includes the choroid (a thin, dark layer containing blood vessels behind the retina), the ciliary body (which produces fluid in the anterior chamber of the eye and helps support the lens), and the iris (the tissue that forms the pupil). The pupil is the opening at the center of the iris (or the black dot), primarily responsible for regulating the amount of light the eye receives. The internal neural coat at the back of the eye is the retina. The retina, akin to the film in a camera, transmits electronic images to the brain via the optic nerve.

The internal structure of a cat's eyes can be divided into three chambers: the anterior chamber, the posterior chamber, and the vitreous chamber. The anterior chamber is located between the cornea and the iris and contains aqueous humor (a transparent fluid produced by the ciliary body). The posterior chamber is situated between the iris and the lens and also contains aqueous humor. The vitreous chamber is behind the lens and in front of the retina. This gellike substance helps maintain the eye's round shape.

Other important structures within a cat's eyes include:

1. The orbit, which is the bony cavity that contains and protects the eye.

2. The eyelids, which are extensions of facial skin used to protect the eyes. The outer surface is covered with skin, while the inner layer is a pale, pink conjunctiva.

3. The third eyelid, originating from the inner corner of the eye, features a robust cartilage support and tear glands. It also serves as an additional protective mechanism for a cat's eyes.

4. The conjunctiva, a thin, nearly transparent, vascular tissue that covers the white part of the eye and the eyelids.

5. The lens, a soft, transparent, spherical structure suspended within the eye just behind the pupil. The lens is primarily responsible for focusing light entering through the pupil onto the retina at the back of the eye.

6. The lacrimal system, which includes the lacrimal glands and the glands within the third eyelid, responsible for producing tears and draining them from the eye.

What are the functions of a cat's eyes?

The primary function of a cat's eyes is to enable the animal to see or have visual perception. The ability to see depends on the activity of several structures within and around the eye. When a cat looks at an object, light reflects off the object onto the cornea. The light is bent by the cornea and then enters through the pupil into the lens, and finally through the vitreous into the retina.

The lens ensures that light is clearly focused on the retina. The image received on the retina is inverted, and it is the brain's responsibility to flip the image so that the cat can see it correctly. The retina contains millions of lightsensitive receptors called rods and cones. Rods are sensitive to dim light, while cones are sensitive to bright light and color. The retina converts light energy into electrical signals, which are then transmitted to the brain via the optic nerve. In the brain, these electrical signals are converted into images that can be perceived in an upright position.