Labrador Eye Health

Many of you may have experienced eye problems with your labrador, some of which can be quite common. In this article we are going to discuss the structure of a dogs eyes, and a few of the many eye problems which may occur in dogs in general, and more specifically, labradors.

How Does My Labs Eye Function?

The function of the eye is to allow your dog to see or have vision. The ability to see is dependent on the actions of several structures in and around the eyeball. When you look at an object, light rays are reflected from the object to the cornea. The light rays are bent (refracted) by the cornea and directed through the pupil to the lens, and then through the vitreous to the retina. The lens' job is to make sure the light rays come into focus sharply on the retina. The resulting image on the retina is upside-down and it is the brain's responsibility to turn the image so that you see the image correctly. The retina contains millions of light receptors called rods and cones. Rods are sensitive to dim light and cones are sensitive to bright light and colors. The retina converts light energy into electrical signals and sends them to the brain via the optic nerve, which is the nerve that runs from the eye to the brain. In the brain the electrical signals are translated into an image that is perceived in an upright position.

Eye Problems That Can Affect Labs

Eye Discharge

Like their owners, labradors sometimes wake up with 'sleepers' in their eyes - a crusty discharge that results from the eye's natural self-cleaning efforts. All dogs will get this from time to time, and it is perfectly normal. There are some bulgy-eyed breeds such as pugs and pekingese that are much more prone to it than others. If your labrador has 'sleepers' in their eyes, simply wipe their eyes gently with a damp cotton pad, to remove any discharge. If thy don't produce a build up of discharge to any extent during the day, then you generally don't have to worry about it.

If your labs eyes have a discharge throughout the day, they may have an infection. Eye infections are fairly common. They can crop up on their own or when something lodges in the eye. They can also occur when the surface of the eye, called the cornea, gets scratched. A telltale sign of infection is the appearance of the discharge: It will often be thick, yellow, gray, or green. It may form a crust on the eyelids as well.

Cataracts - Like a camera, eyes have a clear lens inside them that is used for focusing. A cataract is any opacity within a lens. The opacity can be very small (incipient cataract) and not interfere with vision. It can involve more of the lens (immature cataract) and cause blurred vision. Eventually, the entire lens can become cloudy, and all functional vision lost. This is called a mature cataract. Most cataracts in dogs are inherited. The cataract may develop rapidly over weeks, or slowly over years, in one or both eyes.Like humans, dogs also develop cataracts with age (often after 8 years of life).Cataracts can also develop in dogs with diabetes mellitus or in orphan puppies on an artificial milk replacer diet.

Distichiasis - Distichiasis is the term used to refer to extra hairs growing on the edge of the eyelid. Distichiasis causes irritation. This usually shows itself in the dog as an increase in blink rate, holding the eye partly closed and increase in tear production showing itself as tear overflow or a "tear streak".

Retinal Dysplasia - Retinal dysplasia is the most important retinal disease affecting Labradors used for hunting and field trial work. The condition is relatively uncommon in lines of Labradors used for conformation work. Retinal dysplasia is a widespread inherited condition in the Labrador. Retinal dysplasia involves abnormal development of several structures of the visual system. Dogs may be very mildly affected and demonstrate folds in the retina. These are areas where extra retina develops and instead of forming a thin membrane over the back surface of the eye, the extra retina develops into folds. This fold results in a blind spot. Retinal dysplasia involves abnormal development of several structures of the visual system. Dogs may be very mildly affected and demonstrate folds in the retina. These are areas where extra retina develops and instead of forming a thin membrane over the back surface of the eye, the extra retina develops into folds. This fold results in a blind spot. Often times the retina is also undernourished and an area of retinal degeneration will occur.

Dogs with mild changes (i.e. a few retinal folds), usually have no visual compromise. Subtle changes on the part of the dog, on the positioning of the head while marking a bird, help affected Labradors make use of normal areas of the retina. Larger blind spots may cause dogs to miss a mark or miss stationary objects, while these dogs are able to perceive moving objects with less difficulty.

The retina is a membrane which lines the back of the eye and contains the light receptors needed for vision. Progressive Retinal Atrophy (PRA) and Central Progressive Retinal Atrophy (CPRA) are diseases which progressively destroy these light receptors resulting in gradual loss of vision and blindness. Both PRA and CPRA are inherited conditions and have been seen in several breeds including Labrador Retrievers. If your lab has one of these diseases they are capable of transmitting the disease to their offspring if mated with a lab carrying the trait for the disease.Any dog having one of these diseases is capable of transmitting the disease to his offspring if mated with a dog carrying the trait for the disease.

Eye Examinations to detect PRA/CPRA

Dry Eyes- Some dogs will develop eye disease when normal tear film production is reduced. The lack of tears causes the cornea of the eye to become dry and damage to the cornea then occurs. This condition is commonly called Dry Eye. Dogs with this condition will show obvious irritation of the eyes, with thick yellow discharge being produced. Ulceration of the cornea is common, the cornea looks dry and loses its normal shiny appearance. The nostril on the affected side is usually dry too because normally, tears flow from the eyes, through the tear duct, to the nostrils.

Eyelid Problems- Abnormalities of the eyelids are a common cause of eye disease in dogs. The eyelids may roll inwards so that the hairs of the face rub against the eyeball. As you well know, having a hair in your eye is a painful condition. Imagine what it is like to have several hairs constantly rubbing against your eye! This condition is called Entropion and is corrected by careful surgery.

Structures Of A Dogs Eye

•   The orbit is the bony cavity that contains and protects the eyeball.
•   The eyelids are extensions of the skin of the face, and they are designed to protect the eye. The outer surface of the eyelid is covered with skin and sometimes contains the cilia (eyelashes). The inside is lined with a pink-white colored conjunctival membrane.
•   The nictitans or third eyelid arises from the inside corner of the eye and contains a strong cartilage support and a tear gland. It is also designed as an extra protective mechanism for the eye.
•   The conjunctiva is a thin, nearly transparent, vascularized (containing blood vessels) tissue that covers the white of the eye and lines the eyelids.
•   The lens is a soft, transparent, spherical structure that is suspended within the eye just behind the pupil. The lens is responsible for focusing light coming in through the pupil onto the retina in the back of the eye.
•   The lacrimal system, which includes the lacrimal (major tear) gland and the gland of the third eyelid, is responsible for tear production and drainage of tears away from the eye.
  

If you notice a problem with your labradors eyes, seek advice from your vet who will examine your labrador and advise accordingly.

Disclaimer:
Please note, all of the above information has been written as a guide only, please consult your vet with any further questions you may have about your labs eyes, and always follow the advice of your own vet, as they will know your labrador best.