Two important congenital disorders that affect the optic nerve and optic disk in dogs are Coloboma which is a localized absence of optic nerve tissue, and optic nerve hypoplasia marked by underdevelopment of the optic nerve. The nerve may also be impaired by:
- Inflammation (Optic Neuritis)
- Swelling (Papilledema)
- Shrinkage (Optic Atrophy)
What Is Optic Nerve Hypoplasia?
Optic nerve hypoplasia is a relatively rare condition and may be unilateral (one eye is affected) or bilateral (both eyes are affected). In this condition, the optic nerve appears extremely small because of its underdevelopment. Either eye can be affected by this congenital abnormality, and affected eyes frequently are blind.
Signs & Symptoms
Because blindness in one eye is compensated by sight in the other, hypoplasia affecting only one eye often will go undetected. Affected eyes have reduced numbers of retinal ganglion cell axons. Resting pupil size may be normal, being regulated from the opposite eye, or dilated, with bilateral optic nerve hypoplasia. Examination reveals a small or barely detectable optic nerve. The retinal blood vessels are present, but the number of arterioles and veins may be reduced. There is no effective therapy for this condition.
Susceptible Dog Breeds
Breeds affected by the optic nerve hypoplasia include the:
- Great Pyrenees
- Irish Setter
- Miniature Schnauzer
- Norfolk Terrier
- Saint Bernard
- Standard Poodle
- Miniature Poodle
- Toy Poodle
It is best to withhold affected dogs from breeding programs, since the condition is known to be inherited in the Miniature Poodle, while in others it is associated with inherited eye disorders and a broad range of disorders of the central nervous system.
- Mordecai Siegal – UC Davis Book of Dogs : The Complete Medical Reference Guide for Dogs and Puppies
- Kirk N. Gelatt – Color Atlas of Veterinary Ophthalmology