Eye emergencies

Usually only one of the eyes is affected, allowing you to compare easily the affected eye with the healthy eye to see what changes have occurred.

If the eye is painful, the classical signs are that your dog may blink a lot, keep their eyes tightly closed, produce more tears than usual, avoid looking at the light and may not like being touched around the head.

The white parts of the eye may appear red.

Sudden blindness may affect one eye, or both eyes; the dog will be confused and may walk into obstacles on the affected side, or sides. If vision loss is only on one side, you may be able to notice a difference in pupil size between the two eyes. If both eyes are affected, the pupils may appear larger than usual. Many causes of sudden blindness are painless and not all are caused by problems directly related to the eye itself.

Eyeball prolapse (where the eyeball may pop out of position) is most commonly seen in brachycephalic dogs (dogs with a characteristic flattened face and a short muzzle) because the socket of the eye (the orbit) where the eyeball is located is particularly shallow. Unfortunately, the chances of long-term damage to the eye are high, even if the eyeball is quickly returned to the socket.

Traumatic injury to the eyeball is also more common in brachycephalic breeds because their eyes tend to be more prominent. Prominent eyes are often less sensitive, so the dogs may not initially show any major signs of pain, even if there is deep corneal ulceration. However, in many breeds of dog, owners are quick to realise that urgent veterinary assistance is needed, because the eye is clearly damaged.

Damage to the eyelids (third eyelid, upper and lower eyelids) needs veterinary attention quickly, as surgery to restore eyelid integrity will prevent adequate blinking, result in poor tear film distribution and secondary corneal damage can occur.

Traumatic injury to the cornea (the surface at the front of the eyeball) is not uncommon and cat scratch injuries are a frequent cause of corneal ulceration. With the exception of some brachycephalic dogs referred to above, corneal ulcers are usually painful, although they are not always obvious. When there has been deep damage to the cornea, the clear fluid that fills part of the eye ball may escape through the wound until it forms a clot. The colourful part of the eye (the iris) may be caught up in the wound and, if so, the pupil (central black part of the eye) may no longer appear round. All cases of suspected penetrating eye injury should be assessed as a matter of urgency by your local veterinary surgeon to make sure that the lens has not been damaged. When lens damage has occurred, or is suspected, urgent referral to a specialist will be required.

Many kinds of damage to the cornea can result in a corneal ulcer. For example, occasionally hairs, especially those found beneath the eyelid (ectopic cilia) can be painful if they rub against the cornea, especially in breeds susceptible to extra eyelashes (distichiasis).

Complications of corneal ulceration can happen if the cause of the ulcer is not recognised or managed correctly, if the ulceration is not treated appropriately or if it is linked to other diseases, such as Cushing’s syndrome or diabetes mellitus. The ulcer may deepen and the cornea rupture; a situation which requires emergency intervention.

Corneal ‘melting’ is clearly an eye emergency – the greyish, jelly like appearance of the melting cornea is typical, which can lead to corneal rupture if the dog is not hospitalised and treated urgently.

Foreign bodies may be inorganic (e.g. metal and glass) or organic (usually plant material) and as well as being retained in the cornea, they may penetrate more deeply within the eye, or lodge in the eye socket (the orbit).

Plant material, for instance, can become lodged in the visible white of the eye, beneath the eyelids or within the tear drainage system. The dog’s lifestyle and day-to-day activities should be taken into account, especially if the injury comes on suddenly; e.g. when there is shooting in the vicinity, or following a walk in a hayfield or barley meadow.

Swelling of, or around, the eye socket can be painful and the dog may be very reluctant to open its mouth or eat. The insides of the eyelids may become red and swollen, the third eyelid may be more obvious than usual and the eyeball itself may be pushed forward by any swelling. Sometimes a swollen eye socket may be a result of a stick injury that occurred weeks or months before.

Chemical injuries, especially those caused by alkalis, such as oven cleaner or drain cleaner, may cause blindness and are usually very painful. If possible, find out what chemical, or what product, your dog has been exposed to and always ring your veterinary surgeon for advice immediately. If possible, carefully rinse the eye with plenty of water straight away, but this may be challenging depending on how painful the injury is.

The uveal tract is made up of three main parts: the choroid (a layer filled with blood vessels which supplies oxygen and nourishment to the retina), the ciliary body (which produces aqueous humour and changes the shape of the lens) and the iris (the structure responsible for controlling the size of the pupil and defining the colour of the eye). Inflammation of the uveal tract has many possible causes. One or both of the eyes may be involved. If both eyes are affected it may suggest that systemic disease might be present. The classical appearance is of a red painful eye. If only one eye is affected, the pupil may appear smaller than normal on the affected side. The fine detail of the iris may also be lost and iris colour may be altered, usually becoming darker.

Acute glaucoma is usually associated with an increased pressure in the eye and is both painful and sight threatening; it usually affects only one eye initially. The eye may become reddened and the pupil may be larger in the affected eye. Sometimes the surface of the eye may appear slightly blue and there may be partial, or complete, vision loss. Some breeds are more prone to primary glaucoma, but it is most commonly secondary to a number of other conditions, including primary lens luxation, severe uveitis, neoplasia and pigment migration. In dogs with primary lens luxation the lens may be seen to be positioned abnormally within the eye.

Sudden loss of vision may happen in either one or both of the eyes, although it is not always easy to be sure that the eye is blind when only one eye is affected. As well as the causes already listed (traumatic and chemical injuries, inflammation and glaucoma), bleeding in the eye and retinal detachment are other possible reasons for blindness. Problems with the central nervous system, inflammation, tumours and increased pressure around the brain (intracranial pressure) could all cause sudden blindness. Various poisons may also cause vision loss.

However, sudden retinal degeneration (SARDS) is a syndrome of unknown cause which is most common in middle-aged and older dogs, especially those with a recent history of weight gain. It is probably the most well known, although not well understood, or treatable, of conditions causing sudden onset blindness. The only clinical signs the owner may notice initially in dogs with SARDS are moderately larger pupils and problems seeing.

If your local veterinarian is unable to discover the main cause of your dog’s blindness then they may need to carry out more investigations into your dog’s general health.