Inherited Ocular Diseases, Dr. Cheryl Cullen, BSc, DVM, MVetSc, Diplomate ACVO

THE EYES OF A DOG are located within a protective bony socket called the orbit. In addition to the orbital bones, the eye is protected by upper and lower eyelids.

The exposed portion of the eye is covered with tears, which are made up of three main layers: a fatty layer, a water layer and a mucous layer. The eyelids protect the eye and distribute the tears across its surface to keep it moist.

The eye itself is made up of three main layers: the outer layer, called the fibrous coat; the blood-vessel­ rich layer, called the uvea; and the inner nervous-tis­sue layer at the back of the eye, called the retina. The retina has special receptors called rods and cones, which provide dim light, and bright light and colour vision, respectively. Contrary to popular belief, dogs have the ability to see not only shades of grey, but also colours, namely blues and yellows.

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