Cataract. A clouding of the lens that obscures vision. Cataracts are the most common cause of blindness in dogs. Most dogs with cataracts inherited the tendency to develop them. Inherited cataracts can occur in the Afghan Hound, American Cocker Spaniel, Boston Terrier, Chesapeake Bay Retriever, German Shepherd, Golden Retriever, Labrador Retriever, Miniature Schnauzer, Norwegian Buhund, Old English Sheepdog, Schnauzer, Siberian Husky, Staffordshire Bull Terrier, Standard Poodle, Welsh Springer Spaniel and West Highland White Terrier. Diabetes, injuries, poor diet and aging can also lead to cataracts.
 
Removing the lens allows light to again enter the eye. For best post-surgery vision, the natural lens is usually replaced by a plastic lens. “The surgery itself is not too stressful for the majority of patients,” says Dr. Lim. However, “the first few weeks postoperatively can be stressful because it is very intensive—the patient must wear an Elizabethan collar at all times, and several medications are required.”
 
Glaucoma. Elevated pressure of the intraocular fluid (fluid inside the eyeball) caused by fluid draining more slowly than it is produced. Glaucoma can damage the retina or optic nerve.
 
Most often, a dog gets glaucoma because she inherited an eye structure that leads to poor drainage. Breeds in which primary (inherited) glaucoma occurs include the Alaskan Malamute, American Cocker Spaniel, Basset Hound, Beagle, Boston Terrier, Bouvier des Flandres, Chow Chow, Dalmatian, English Cocker Spaniel, English Springer Spaniel, Great Dane, Labrador Retriever, Norwegian Elkhound, Poodle (all sizes), Samoyed, Shar-Pei, Shih Tzu, Siberian Husky and Welsh Springer Spaniel.
 
Primary glaucoma has no obvious cause and affects both eyes, although one eye may develop glaucoma earlier than the other. Secondary glaucoma is glaucoma that is caused by a dislocated lens, injury, tumor or other problem that decreases fluid drainage in the eye; it may affect just one eye.
 
Four types of glaucoma occur in dogs. In open-angle glaucoma, pressure builds and damage occurs slowly. The American Cocker Spaniel, Basset Hound, Beagle, Boston Terrier, Miniature Poodle, Miniature Schnauzer and Norwegian Elkhound are prone to this type. Narrow-angle (also called closed-angle) glaucoma is more common. It is an emergency in which glaucoma comes on quickly and painfully and causes serious damage within as little as a few hours. Dogs prone to this type are the Alaskan Malamute, American Cocker Spaniel, Basset Hound, Chow Chow, Dalmatian, English Cocker Spaniel, Fox Terrier, Great Dane, Poodle (all sizes), Samoyed, Siberian Husky and Welsh Springer Spaniel. The third type is goniodysgenesis, in which a ligament in the eye is defective and may cause partial blockage of drainage. The American Cocker Spaniel, Basset Hound, Bouvier des Flandres, Chihuahua, Chow Chow, English Cocker Spaniel, Norwegian Elkhound, Poodle (Toy and Miniature), Samoyed, Siberian Husky and Terrier (some breeds) are among the breeds prone to this type. In pigmentary glaucoma, an excess of pigment cells block drainage. Cairn Terriers are prone to this type.
 
Glaucoma treatments include surgery, pills, eye drops or (rarely) removal of the eyeball. “Glaucoma is still one of the more difficult things to handle,” says Dr. Vainisi. “Even though there are literally dozens of glaucoma procedures, there still is not that ideal one … even in humans.”