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  • Jo De Klerk

    Common Dog Eye Conditions

    The eyes are two structures that are so vital to your dog’s ability to perceive their surroundings. On a normal basis, he shouldn’t be able to feel his eyes, but if there’s something wrong, they can be excruciatingly painful. The cornea (outside layer of the eye) has one of the most densely packed areas of nerves in the whole body. This means that even a tiny scratch can lead to excruciating pain, and needs swift medical attention.

    The eye is made out of several structures. As we’ve already mentioned, the outside layer is called the cornea. The inside of the eyelids is lined with the conjunctiva. When you look at the eye, the black part in the middle is called the pupil, which is not black, but instead a hole to the back of the eye where the light enters. Around this is a coloured part of the eye, known as the iris, and the function of the iris is to cause the pupil to get bigger and smaller, to let in more or less light. Across the pupil is a clear structure called the lens. This bends the light as it passes through, to focus it on the retina at the back of the eye. The retina is a layer which is full of nerve endings. This is the structure that converts the light into a signal to the brain for processing. Normally, all these structures work harmoniously together, but when there is a problem, it is very obvious to your dog.

    Here are the five most common conditions why a dog will need to see their vet about their eyes:


    Conjunctivitis translated means the inflammation of the conjunctiva. As we’ve already mentioned, the conjunctiva is a lining of the eyelids. When it becomes inflamed, it turns a dark pink or red colour and can be very sore. It can cause the eyes to produce mucus, which may be green, yellow or white, and collect in the inner corner of your dog’s eye. This needs to be cleaned away daily to prevent skin infections in this area.

    Conjunctivitis is most commonly caused by an infection, usually bacterial, although not always. A veterinarian will first check that the eye hasn’t had any trauma to it, that has got infected. He will do this using a stain. If the conjunctivitis has been going on for a while, he may also take a swab to send off to the laboratory to be cultured for bacteria, but for most conjunctivitis conditions, they will clear up with daily drops which your vet will prescribe.

    Corneal Ulcers

    A corneal ulcer is one of the sorest eye ailments that your dog can experience. Even tiny ulcers can cause great pain. Ulcers can arise for many reasons. The most common reason is because of a traumatic abrasion. This could be from something as big as a stick which your dog’s eye contacted on a walk, or as small as dust. Another common reason is because of an object getting stuck in your dog’s eye. Grass seeds are common foreign bodies, and they commonly get stuck under the third eyelid. Finally, if your dog has an underlying condition, such as Dry Eye (talked about in the next section), or protruding eyes, such as in Pugs and French Bulldogs, they can be prone to developing ulcers due to dryness.

    Like conjunctivitis, your vet will probably start by investigating the amount of damage to the eye with a stain. This will be orange or green in colour and fluoresce when he shines a blue light on it. If he thinks there might be something in the eye contributing to the damage, he is likely to also put in some local anaesthetic, and use a cotton bud to check underneath the eyelids.

    Most corneal ulcers will heal up very quickly with eye drops to prevent infection and promote healing, but in rare cases, surgery might be needed to remove loose flaps of the cornea which may be causing a problem.

    Dry Eye

    Also known as Keratoconjunctivitis Sicca (KCS), dry eye is a disease that some predisposed breeds of dog may go on to develop. The medical term essentially means ‘inflammation of the cornea and surrounding tissues due to drying out’. It is due to inadequate production of tears from the lacrimal gland and/or the tear gland in the third eyelid. This is usually due to immune-mediated destruction of the glands or in other words, the body’s immune system attacking and destroying the glands.

    Tears are needed to lubricate the eye and remove debris which may have come into contact with the eye surface. Tears are made up of water, mucus, and fatty substances. When there are not enough tears in the eye, your dog will have painful eyes and he may be red and squint or blink excessively. There is usually a discharge from the eye, which is the mucus part of the tears that no longer has water in it.

    In severe cases, as mentioned earlier, ulceration may also happen, which might lead to scarring of the eye or increased pigmentation. If it is very extensive, the eye may also have a blue hue to the outside of it. The eye will also have numerous tiny blood vessels going to the area where it is ulcerated to try to bring nutrients to the area to heal it. Both eyes are usually affected, however, one is often worse than the other.

    Dry eye can be easily diagnosed based on the history, clinical signs and a test called the Schirmer tear test. Any veterinarian can carry out this test in a matter of minutes at very little cost. It is a simple test, where a strip of blotting paper is placed under the bottom eyelid for one minute, and it measures the volume of tears produced and absorbed within that time frame.

    There are two aims of treatment for dry eye; firstly, to increase tear production and secondly to replace the tears. There are several types of eye drops available that stop the body from attacking the tear glands, thereby allowing them to function again to some degree. These are usually used in combination with replacement tears to keep the eye moist. These drops require lifelong administration, although once any ulcers have healed up and the eye is less painful, the drops can usually be reduced to just several times per day, rather than every few hours.

    Cataracts and Nuclear Sclerosis

    Both cataracts and nuclear sclerosis are conditions of the lens. Normally the lens is clear, but in these cases, it appears cloudy. The difference is, with cataracts the cloudiness is opaque, whereas a dog with nuclear sclerosis will be able to have some vision.

    Nuclear sclerosis is a normal part of aging and is of no concern. It is when the fibres of the lens condense together. Cataracts, on the other hand, are not normal, and underlying medical conditions such as high ocular pressure or diabetes should be investigated and ruled out. Some dogs don’t have underlying issues, but instead, their cataracts are related to genetic predispositions. There are no medical options for the treatment of cataracts once they form, however, it is possible to surgically replace the lens under the treatment of a veterinary ophthalmologist.


    Glaucoma is when the pressure of the eye is high. This can be due to many reasons. The most common reason is because of high blood pressure, however primary eye problems can also cause glaucoma, such as eye tumours pressing on the eye or luxation of the lens.

    Glaucoma is extremely serious, and while drops can be given by your veterinarian to reduce the pressure, the underlying cause should be investigated and treated. Glaucoma might not be externally obvious, but in some cases, the eye may be cloudy and there may be excessive tears from the pain. If the drops do not work, and addressing the underlying issue does not make a difference, then in some cases, the eye might have to be removed.

    How Do You Give Eye drops?

    Your vet is likely to prescribe some eye drops to treat your dog’s eye. Before applying the drops to your dog’s eye, ensure that you read both the package instructions and your veterinarian instructions. Some drops may require storage in the box, out of light, and some may require storage in the fridge. Ensure that you apply the drops to the eye as frequently as your veterinarian advises. You can do this by cleaning the discharge away from the eye, then tilting your dog’s head upwards and applying the drops to the centre of the open eye.

    If you do not see a marked improvement in 24-48 hours, then you should revisit your vet, because luckily for your dog eyes heal quickly, and therefore they should have made an improvement by then.

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    Jo De Klerk

    Jo is a graduate of the Royal Veterinary College, London. She has a Masters degree in Tropical Animal Health, and has spent most of her career working in mixed veterinary practice.

    Recently, she has become involved in one of the UK’s fastest growing veterinary telemedicine services for dogs and cats.

    She is a published author of several books, and enjoys working as a freelance veterinary writer around her clinical work.

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