The lacrimal glands produce, throughout the day, tears which will form a natural protection for the eye: the lacrimal film.
A lack of secretion of these tears will cause an ocular dryness itself responsible for inflammation of the conjunctiva and the cornea. This condition is called dry keratoconjunctivitis.
What is the use of tears?
The lacrimal film performs several functions:
A protective role: the permanent humidification of the cornea allows mechanical protection against all types of aggressions (wind, dust ...)
A role of nutrition: tears bring to the cornea the nutrients and oxygen that it needs
An antibacterial action
A cleaning role: the small foreign particles are trapped in the mucus and eliminated by this means
An aid for the sliding of the eyelids on the cornea
When tear secretions fail, these functions are no longer assured and various symptoms appear.
What are the symptoms of dry keratoconjunctivitis?
The dog suffering from dry keratoconjunctivitis has several symptoms:
- The affected eye is red. Signs of "discomfort", pain are noted (the animal regularly blinks eyelids, it frequently rubs the eye with the paw)
- Streams of mucus (or even pus when superinfection is present) stick to the eyelids and make it look dirty permanently
- The eye loses its smooth and shiny appearance
- The cornea loses its transparency: whitish stains appear first in some places then an "opaque film" gradually covers almost the whole cornea
- Small vessels develop on the surface of the eye
- In advanced stages, the dull and irregular cornea is covered with brown spots, this pigmentation being accentuated with time
- Finally, corneal ulcers may develop
Origin of dry keratoconjunctivitis
Some breeds are predisposed as Poodle, Cocker, West Highland White Terrier as well as many brachycephalic breeds (dogs with short snouts) among which the Shi Tzu, Pekinese, King Charles Cavalier, Lhasa Apso, Bull Dog ...
Several causes can be at the origin:
Immune: this is the most common cause of dry keratoconjunctivitis. The immune system of the eye attacks by mistake the lacrimal glands. The associated inflammation causes their progressive destruction and therefore the decrease in tear secretion
Aging: the lacrimal glands degenerate gradually with time
Anomalies of development: since lacrimal glands have not been formed normally during the development of the embryo, a lacrimal gland may, for example, be absent at birth
Endocrine imbalance: including Diabetes or Cushing's Syndrome
General Illness: Sickness, Leishmaniasis ...
Medicinal: For example, when administering anti-epileptics or prescribing prolonged use of certain antibiotics of the sulphonamide family
In all these cases, the pathology is very often bilateral
In other cases of dry keratoconjunctivitis, only one eye is affected, especially when the origin of the disease is:
Neurological: during paralysis of certain nerves of the face (other symptoms are then also present)
Trauma: the trauma causes an important inflammation of the conjunctiva, itself responsible for a partial destruction of the lacrimal glands
To demonstrate dry keratoconjunctivitis, your veterinarian will perform a test called "schirmer test":
A small graduated absorbent strip will be placed between the eye and the eyelid of the animal for 1 minute and collect the secreted tears in this period of time.
The quantity of tears produced in one minute can then be evaluated and compared with the established standards (15 to 20 mm / min in dogs and 10 to 15 mm / min in cats)
Careful examination of both eyes will then look for possible secondary lesions such as:
- pigmentation or the presence of small vessels on the surface of the cornea
- the presence of corneal ulcers revealed by a fluorescein test:
This colored product attaches itself to the injured areas of the cornea, making it possible to demonstrate the presence of any ulcers.
Your veterinarian will seek, during the consultation, a specific condition or cause that may explain the presence of dry keratoconjunctivitis. Thus, if a drug can be incriminated, it will, as far as possible, be stopped. Similarly, if other symptoms are associated with keratitis, a general disease will be considered and its treatment instituted.
The treatment can then be put in place.
It is based on:
The application, morning and evening, of cyclosporine-based ophthalmic tear ointments
- This molecule stops the process of autoimmune destruction of the lacrimal glands (it is therefore particularly useful in dry keratoconjunctivitis secondary to an immune disorder)
- It stimulates the secretion of tears
- It limits the inflammation
- and makes it possible to combat the superinfections
The instillation, several times a day, of tear substitutes which will play the part of the tears naturally secreted by the lacrimal glands
For optimum results, these tear ointments and gels should be administered at least one hour apart from each other.
Your veterinarian will evaluate the effectiveness of the treatment by performing a new shirmer test:
- If the secretion of tears is always very weak, the lacrimal glands are destroyed; Only treatment with tear substitutes will be maintained.
- If the result of the schirmer test has improved significantly, treatment with cyclosporine is continued. Stopping the administration of the ointment is usually accompanied by a new lacrimal deficiency, and this treatment must therefore most often be maintained for life.
Antibiotic and anti-inflammatory eye drops are associated with cyclosporine ointments and lacrimal gels to treat secondary lesions (bacterial superinfection, neovascularization on the surface of the cornea ...)
Finally, surgery is sometimes necessary:
- During deep ulceration, the eye will be temporarily closed to facilitate the healing of the cornea
- When pigmentation causes significant visual discomfort, the pigmented areas can be removed surgically
- In dry keratoconjunctivitis refractory to any medical treatment, a salivary canal may in certain cases be deflected in order to bring it to the level of the eye and thus ensure a humidification of the cornea
Untreated dry keratoconjunctivitis has many repercussions: chronic pain, repeated infectious conjunctivitis, loss of transparency and corneal pigmentation, resulting in decreased vision, corneal inflammation that can cause ulceration or even perforation of the cornea ...
Do not hesitate to consult your veterinarian with any sign evocative of this affection (red eye, painful, dirty, dull, pigmented ...)