Question and Answer – Eye problems

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Dear Your Own Vet,

My cat suffers from eye discharge a lot. How do I know which eye problems are emergencies and which ones aren’t? If I use an ointment or eye drops at home, how do I know which eye drops to use?

Karin Mayers



Dear Karin,

Always phone your vet to check which eye drops to use, as the wrong eye drops can damage your pet’s eye. The most common eye problems that are seen in animals are:














Conjunctivitis is inflammation or infection of the conjunctiva. The conjunctiva is the soft pink lining inside the eyelid. When it is inflamed, you may see:

feline Herpes infection causing conjunctivitis

Note the eye discharge, and closed eyes in a cat with conjunctivitis

discharge from the corner of the eye which may be pussy or clear

redness of the inner eyelids

swelling or bulging of the inner eyelids

the eyes may be sensitive to light

the eyelids may be half closed

the third eyelid (the fleshy pink part in the corner of the eye) may be swollen or protrude over the eye itself

The most common causes of conjunctivitis in cats are Feline Herpes virus or Feline Chlamydia infection. Together the two are known as “Snuffles” or “Cat Flu” in some countries. Dogs can also get contagious conjunctivitis. If the animal is not showing any other signs of illness, and only has an eye infection, the owner is usually given eye drops to put into their pet’s eyes a few times a day. These eye drops usually contain antibiotics.

Avoid: Boracic acid is not recommended for pet’s that have conjunctivitis.

swollen conjunctiva in cat with herpes infection

Note the swollen conjunctiva or eye membranes with a severe conjunctivitis


Ulcers on the eye can be caused by a direct injury to the eye but can also be caused by feline Herpes virus. (You see a conjunctivitis combined with an ulcer on the eye’s surface) Ulcers on the eye are on the layer of the eye known as the cornea, which is the clear covering over the whole surface of the eye, that protects the delicate structures underneath. A hole or graze on the cornea is called an ulcer. Boxer dogs are prone to ulcers that will not heal with eye drops and other conservative treatments, and need surgery done on the cornea in which little striations or tiny cuts are made over the ulcer and cornea, stimulating blood flow and healing of the ulcer.  Ulcers are usually diagnosed with a dye called “Fluorescein” which is a luminous orange dye that goes bright green when it stains an ulcer up.

fluorescein staining ulcer cornea dog

An ulcer on the eye surface (cornea) stained green with fluorescein to show up.

Ulcers that are small and shallow pose no real threat to the eye and uncomplicated uninfected ulcers heal with antibiotic eye drops over about a week. Ulcers that are infected can get worse, and that means larger and deeper. If an ulcer goes too deep, it eats through the whole thickness of the cornea and exposes the delicate parts of the eye underneath. This is an eyeball emergency and will also need surgery – a small area of the conjunctiva can be stitched over the defect in the cornea bringing blood to the area and allowing it to heal. If the ulcer goes right through the cornea, a pink membrane called a descemetocoele will poke out through the hole and if it goes through that membrane then the eyeball can rupture and the whole eye will have to be removed.

Avoid: Any eye drops that contain cortisone as these will make the ulcer far worse

DRY EYE (Keratoconjunctivitis Sicca/KCS)

Tears are normally produced by the eye to wash away dirt and bacteria on the surface of the eye, as well as to lubricate the eye’s surface so the eyelids can open and close more easily. There are a number of tear glands around the eye and excess tears drain through the tear duct or lachrymal duct in the corner of the eye down into the back of the nose and throat. Sometimes the tear glands can be attacked by an immune process that stops tears being produced.

KCS keratoconjunctivitis sicca

Note the redness of the  eye and the mucky discharge from dirt and infection the tears would normally wash away

If the tears stop being produced the eye dries out and becomes painful and infected. Dry eye is diagnosed by doing a tear test –  a soft piece of filter paper with dye marks on it is put into the eye and kept there for up to a minute. A normal eye will tear excessively and the dye will run up the strip.  A dry eye doesn’t do that.  Animals left without treatment can develop ulcers on their eyes that can rupture through the cornea, and the eyeball has to be removed.  It is more a problem in dogs than in cats. The eye is treated initially to get rid of any infections and to heal up ulcers with replacement tears and antibiotics and then stimulated to produce tears again using  a drug that suppresses the immune process attacking the tear glands, such as Cyclosporin or Tacrolimus eye drops given a  few times a day. Once the infection has cleared and the ulcers have healed, most dogs stay only on the immunosuppressive drops for life but sometimes have to use artificial tears or teargel as well.

Avoid: Missing any treatments of drops as missing treatment can lead to a lot of pain for your pet.

PANNUS (Chronic Superficial Keratitis)

Pannus is a disease that occurs in dogs, often German Shepherds or Pugs. It is a slow inflammation of the cornea that leads to a membrane growing over the eye and eventually causes blindness. It starts as a pink membrane with veins in it and gradually gets darker and eventually becomes completely black. It often starts on one corner of the eye and grows diagonally over the eye over time. It is caused by an immune process in some cases and is also seen in eyes that take a lot of damage, such a breeds with eyes that protrude out like the Pug or in a mild dry eye that has been slightly dry for a long time.

superficial keratitis

Note the black membrane growing over from the corner of the eye

If animals live at a high altitude or are exposed to lots of ultraviolet radiation, it can cause pannus to develop as well.  It isn’t painful and is quite easily treated with eye drops, either cortisone based drops such as “Pred Forte” or immunosuppressive eye drops such as Tacrolimus or Cyclosporin. Animals on these eye drops are on treatment for life.  Often the cortisone eye drops are used initially to clear the pannus up, and followed by the immunosuppressive drops, to keep it at bay.

Avoid: Missing treatments of eye drops and stick to a strict regimen to get this under control


If the eyeball comes out of it’s socket, it’s an emergency! This usually happens in breeds such as the Pug, Shih Tzu and Pekingese because they tend to have eye sockets that are a lot shallower than for example, the Bull Terrier. If they are attacked by a  big dog who bites them round the eye , or struck by a car, the eyeball can literally “pop” out of its socket. The muscles that hold the eye in place can tear as well. The eyeball that is hanging out of its socket is very prone to getting damaged as it is exposed to hair and dirt that it would normally be protected from. It also dries out very quickly without the protection of the eyelids. The large artery and nerve that supply the eye are stretched so the eye receives a poor blood supply during this time.

eyeball that has popped out

An eyeball that has popped out (proptosis) is an emergency

The torn tissues round the eyeball and the poor drainage out of the eye (the vein is also stretched and cannot drain blood out the eye) make the eyeball swell up very quickly. If this happens to your dog, and you manage to get your dog into a vet quickly, there is a fair chance that the eye might be saved. Put a damp cloth or cotton wool on the eye surface and bring him straight in.  If a number of hours have elapsed or the pupil is fixed and dilated, the chances are slim that the eye will be saved. Your vet needs to put your dog under general anesthetic and replace the eyeball in the socket. He/she will then sew the eyelids together and recheck your dog in a few days time to see what damage has occurred and send your dog home with antibiotic drops to put in between the eyelids up to 4 times daily. Anti inflammatory painkillers such as Carprofen (Rimadyl) are often given at the same time.

ENTROPION (Eyelids that turn in)

In certain dog breeds that have a lot of facial folds, such as the Shar Pei, the Boerboel, the Bulldog, Retriever and the Mastiff, the folds are so excessive that even the eyelid literally folds over into the eye.

Entropion eye problems shar pei

Shar Pei dog with many facial folds – these dogs often get Entropion

The hairs ands eyelashes rub continuously on the eye causing tearing, eye infections and ulcers to form on the eye’s surface. When puppies are a few weeks old, a tacking stitch may be put in the eyelids to encourage them to grow correctly. In adults, the only way to correct this, is to do a surgical “Tuck” on the skin around the eye, so that the eyelid folds back the way it should. This is a great operation to do, as it gives the animals so much relief afterward and sorts out the continual tearing and eye infections permanently. Once the operation has been done, an Elizabethan collar is put on the dog for 2 weeks to stop him scratching the stitches out. If the eye is infected or ulcerated, drops are given at the same time to clear those up as well.

Eyelid turning in with entropion

Note how the lower eyelid rolls over onto the eye and the blue color of the eye from damage from the eyelashes

GLAUCOMA (increased pressure in the eye)

Glaucoma is an increased pressure within the eyeball itself, which makes the eyeball swell up and appear larger than the other eye and also bulge more out of the socket. The eyeball is filled with fluid – there are two types of fluids in the eye – aqueous humour which as watery and vitreous humour which is like jelly. The fluid is refreshed all the time, new fluid gets produced and fed into the eyeball and old fluid gets drained out.  Usually glaucoma occurs when there is a problem with draining the fluid out of the eye, new fluid comes into the eye but the old fluid can’t get out. This can happen if there is inflammation or infection in the eyeball which makes clots which block the drainage duct, or a growth inside the eye or an injury to the eyeball causing bleeding in the eye. Sometimes with inflammation or damage to the eye, the lens moves and physically blocks the drainage duct. This is called secondary glaucoma i.e. – something happened inside the eye to cause blockage. Sometimes glaucoma happens spontaneously due to genetics for example, and this is called primary glaucoma.  Glaucoma is unfortunately picked up a lot earlier in humans than in pets, because people notice their vision being affected. Most pet owners only notice a problem when it is in its final stages and  a lot of damage has already occurred inside the eye. The increased pressure in the eye pushes on the delicate retina, damaging the cells vital for vision.

enlarged eyes with glaucoma

This dog has glaucoma in both eyes. Note how large the eyes are

Signs of glaucoma in pets:

A very large eyeball which protrudes out compared to the opposite eye

Pet seems off color or grumpy

The pupil is often dilated

The eye appears to be very red and the veins in the white of the eye are prominent

Treatment of glaucoma:

There are two elements to treating glaucoma – with primary glaucoma, medications are given in the form of eye drops to decrease the pressure of the eye.  Example so drugs that are used to treat glaucoma include “Trusopt” (Dorzolomide Hydrochloride) or “Cosopt”. These drops help to reduce pressure within the eye. Painkillers may also be prescribed by your vet. Some veterinary ophthalmologists may do surgery on the eye to treat the glaucoma.

Diagnosis of glaucoma:

Besides the obvious clinical sign of glaucoma, your veterinary ophthalmologist may test the pressure inside the eye with special instrumentation placed on the surface of an anesthetized eye.


Cancer can  occur anywhere in the eye. The most common types of cancers I have seen are:

Squamous cell carcinoma (skin cancer)  of the eyelids:

This occurs in white animals with non pigmented eyelids who live in climates with a lot of sunlight and ultraviolet radiation. The cancer starts off as what looks like a small sore on the eyelid or even on their third eyelid (fleshy part of the corner of the eye), which doesn’t heal and gradually gets bigger and bigger, crusted and starts to irritate the dog or cat, and they rub the eye a lot, leading to tearing of the eye.  These cancers tend to get bigger and spread locally. If left alone, it eats away at all the tissues in the area, gradually enlarging and may get infected. Treatments include surgery, radiation or cryotherapy (freezing).


Melanomas of the eye can be malignant and usually if they are inside the eyeball the entire eye has to be removed.

Retrobulbar tumors (Tumors behind the eye)

Tumors behind the eye push the eyeball forward, and can look very similar to a glaucoma of the eye or an abscess behind the eye. (Retrobulbar abscess).  These are very difficult to treat, the eye has to be removed, the tumor biopsied, and if malignant, the prognosis is guarded as lots of tissue may have to be removed including the bone.


Uveitis is inflammation inside the eye itself.  The eye from the outside looks red and inflamed and cloudy or blue. If your vet looks inside the eye, he/she will not be able to see clearly to the back of the eye because the inside of the eye contains small particles of inflammation (pus or fibrin) and the whole eye is cloudy inside. It can be from an infection, but also as an immune response to something else happening in the body. If left untreated, it can lead to secondary glaucoma or blindness. Treatment unusually involves antibiotic eye drops, atropine eye drops as well as cortisone containing eye drops to reduce the inflammation.


Cherry eye is when the tear gland in the corner of the eye has become inflamed and sometimes everts, causing a red swelling in the corner of the eye.

The lachrymal gland that everts causing cherry eye

The lachrymal gland that becomes inflamed and everts in cherry eye

Treatment is with anti inflammatory eye drops, but may also need surgery, to replace the gland. This surgery may not be successful the first time and may have to be repeated. Some vets remove the gland altogether which is not recommended as it can lead to dry eye.


Cataracts are an irreversible hardening of the lenses inside the eye. If severe, it can lead to blindness. Most old dogs have cataracts to an extent, but some diseases cause cataracts, for example diabetes mellitis.


Note the cloudiness of the lens with a cataract

Injuries to the eye may also cause cataracts. Veterinary ophthalmologists can remove the lenses and also replace the lenses with plastic lenses.  It is recommended that both eyes be operated on as if one is done, disorientation with vision can occur.


Small hairs that grow inside the eyelid and scratch the eye, causing constant tearing and ulcers on the eye. Common in Spaniels The hairs are layered or burnt off under general anesthetic.







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