Several “normal” aging changes occur in the eyes of dogs and cats, just as they do with humans. These conditions, described below, sometimes need to be differentiated from more
The lens is made up of layers of protein. Because the lens cannot enlarge in size, the layers get compacted, leading to scierosis, or hardening of the lens, so that it no longer changes shape in order to focus. As this process progresses, dog and cat owners may note certain behavioral changes. These might include hesitancy with stairs, jumping due to an inability to judge distances, difficulty catching a toy or treat, or “flinching” when approached. Lenticular sclerosis is sometimes referred to as “senile cataracts,” but this term is misleading. A true cataract is an opacity that obscures vision. With sclerosis, the dog or cat shows depth perception problems, but can still see.
The pupil of the iris is made up of a muscle. This muscle frequently thins and atrophies with age, decreasing the pupil’s ability to contract. The decrease in the pupillary light response causes pupil dilation and increased sensitivity to bright light. This naturally occurring iris atrophy and pupil dilation should be differentiated from serious ocular problems, such as glaucoma, inflammation, or neurological disorders.
The cornea is like a sandwich: the outer layer is the epithelium, the inner layer is the endothelium, and the stuffing is the stroma. The stroma is made up collagen layers, arranged in such a way that light passes through. If increased fluid enters the stroma, the collagen layers swell and become disrupted, causing the cornea to become edematous or cloudy with a blue-gray appearance. The endothelium keeps fluid out of the collagen layers; however, it often degenerates with age, so that more fluid enters the stroma than is taken out, leading to the edema. With forward motion, the fluid accumulates under the epithelial layer, forming little bullae, or “water blisters.” If these rupture, corneal ulcers form. This is called “Bullous Keratopathy.” While there is no “cure” for the condition, it may be controlled with hyperosmotic NaCl 5% (salt) ointment. This helps prevent recurrence of ulcers and occasionally facilitates partial clearing. This condition does affect the pet’s vision. With the edema, the cornea is no longer clear, and vision is like looking through frosted glass, causing some distortion of the objects seen. Corneal edema can be seen with more serious diseases, such as glaucoma or intraocular inflammation.
Examination by a veterinary ophthalmologist is recommended if your pet is experiencing any vision problems or ocular discomfort.
Compliments of Nancy M. Bromberg, VMD, MS, DACVO at SouthPaws Veterinary Specialists & Emergency Center 703-752-9100