Retinal detachment (dogs)

The retina is comprised of multiple layers of cells at the back of the eye. Its purpose is to convert incoming light into an electrical signal. The retina converts an image into an electrical signal, which then travels via the optic nerve to the brain, and thus is interpreted as a particular image. In cases of retinal detachment the retina loses its attachment to the back of the eye, an attachment that is crucial for the retinal cells to receive nutrients and survive. The retinal cells also no longer have a connection to the optic nerve and thus any electrical signal they produce will have no way of transmitting to the brain. Therefore vision will be diminished or completely lost.

Retinal detachment mostly occurs when fluid builds up in the space (sub retinal space) between the retina and the underlying layer called the neuroepithelium. This fluid accumulation can create a pressure rise, which may force the retina off the neuroepithelium.

There are a number of different types of fluid which can form in the sub retinal space.
Neoplasia
Either primary (a cancer of the eye cells) or metastatic (a cancer that has spread from a site elsewhere in the body)
Infectious
Canine Distemper, leptospirosis, brucellosis, ehrlichiosis, Rocky Mountain Spotted Fever, aspergillosis, blastomycosis, cryptococcosis, histoplasmosis, coccidioidomycosis, toxoplasmosis, leishmaniasis, neosporosis, any septicaemia (toxins in the blood) or bacteraemia (infection in the blood) and migrating larvae of some nematode (worm) species.
Metabolic
Hypertension, renal failure, hypothyroidism (see related article), hyperviscosity and hypoxia (not enough oxygen in the blood).
Immune Mediated
Systemic Lupus Erythematosus and uveadermatologic syndrome.
Toxins
There have been some reports of drug reactions in dogs that as yet have not been explained. One example is a reaction to trimethoprim-sulphonamide, a common antibiotic. Ethylene glycol (anti-freeze) ingestion has also been shown to result in retinal detachment.
Other
Collie-eye anomaly , severe retinal dysplasia (abnormal development of the retina) and some young animals which may get a congenital or juvenile detachment.
Idiopathic
Some giant breeds of dog have had retinal detachments for which no apparent cause has yet been found.
Rhegmatogenous (retinal tear): A tear will allow the vitreous (viscous fluid that fills the middle of the eyeball) to enter the sub retinal space. Tears may result from age or cataracts. Normally there is a concurrent problem with the character of the vitreous.

Penetrating injuries or foreign bodies, blunt trauma and surgical trauma may all cause retinal detachment, but the problem is usually unilateral (one eye affected).

Traction can cause detachment unrelated to the sub retinal space. When there is a reaction in the eye a fibrous attachment between the retina and another structure may occur. This attachment then only needs to tighten and it will pull the retina off the back off the eyeball.

Signs of retinal detachment will include:
Reduced or lost vision in one or both eyes, (both eyes suggests a systemic problem)
A dilated pupil that does not constrict when exposed to bright light.
Visualizing the detached retina using an opthalmoscope

Reattachment of the retina and a return of vision can occur spontaneously when medical treatment to reduce pressure and inflammation in the eye is initiated. Diuretics and corticosteriods are commonly used. Surgery may be attempted in some cases. Any underlying diseases need to be treated. A prognosis for return of vision is guarded.