Types of dry eye

Dry eye is a fairly complex pathology that requires continuous monitoring. In severe cases, corneal ulcers and opacities may appear, which can lead to significant visual deficits.

Breeds like the French Bulldog are more prone to developing dry eye syndrome.
What is dry eye syndrome?

Dry eye is a complex, multifactorial disease that affects the ocular surface and causes discomfort, visual problems, and, in some cases, lesions in the cornea and conjunctiva.

It is a chronic disease that affects many cats and dogs and requires personalized diagnosis and treatment. Several causes and types of dry eye involve different degrees of severity and require individualized therapeutic strategies to obtain the best results.
Lacrimal glands and ocular surface

Parts of the eye are involved in dry eye syndrome: meibomian glands, ocular surface, and tear film layers.

Despite its name, dry eye is much more than simply "no-tear."

Symptoms

Eye dryness
Redness of the conjunctiva (red eye)
Frequent blinking and the urge to scratch your eyes
Stinging, discomfort, or difficulty keeping your eyes open
Tearing
Increased mucous or mucopurulent secretions (legañas)
Photophobia (abnormal intolerance or excessive annoyance by light)
Loss of vision

In some pets, the discomfort caused by dry eye stimulates the secretion of the main lacrimal gland, paradoxically producing the so-called lacrimation.

These symptoms are often accentuated in situations related to increased evaporation (heat, wind, air conditioning).
According to studies by the UNAM and records of the Conde de Valenciana Ophthalmological Institute, nine out of ten patients suffer from dry eye syndrome, a common disease that worldwide presents 10 to 20 percent of affectation.

Among the most affected are women over 40 years of age due to the hormonal change that generates an abnormal functioning of the tear film and can cause potential damage to the ocular surface.

Diseases associated with dry eye syndrome include rheumatoid arthritis, Sjögren’s disease, systemic lupus erythematosus, and other autoimmune diseases.

As it is a multifactorial condition, a change in ocular humidity can be observed due to climatic changes, use of air conditioning, prolonged use of televisions and computers, and hormonal changes, especially in women.

The symptoms are very clear; there is irritation, eye discomfort, sensitivity to light, itching, and blurred vision that affects the patient’s quality of life and sometimes complicate their daily lives.

Regarding the treatment, an adequate anamnesis should be carried out to diagnose the severity of the disease and thus determine if the invasive or conservative therapeutic line will be used: you can resort to the use of lacrimal plugs, autologous serum drops, or eye drops of immunosuppressive drugs in more severe cases until corneal transplantation if trauma, infections, corneal deformities or degenerations are found.

General protective measures include the use of sun and wind protectors with suitable glasses and identifying and possible exogenous factors such as topical medication and the dry environment.
Causes

Dry eye is generally caused by:

tear deficit (due to lack of production or excessive evaporation)
poor quality tear (lack or alteration of lipids or mucin that make up the tear)
blepharitis (inflammation of the eyelid).

The causes are very diverse and can occur in isolation, or several of them converge.

The main risk factors for dry eye are:

Diseases such as diabetes or hypothyroidism
Advanced age
Allergies
Brachycephalic breeds (with very bulging eyes)
Use of drugs such as eye drops (for glaucoma), sulfa drugs, or antihistamines (for allergies)
Chemotherapy or radiation therapy treatments
Having undergone eye surgery
Environmental factors (air conditioning, heating, dry or highly polluted environments ...)
Diet (vitamin deficiency)
Autoimmune diseases

Types of dry eye

Aqueous: Due to lack of tear production, generally of the aqueous component.

Evaporative: By rapid evaporation of the tear. It is the most frequent reason, caused mainly by the dysfunction of the meibomian glands or by the impossibility of complete blinking (in animals with bulging eyes, etc.).

Inflammatory: Due to clinical or subclinical inflammation.

Neurotrophic: Due to a deficit in the innervation of the cornea, which limits tear secretion and regeneration of the ocular surface.
Ardor, itching, heavy eyelids, eye irritation, blurred vision, and elimination of mucous discharge are manifestations of dry eye syndrome. In addition, although it may seem strange, excessive tearing can also be a symptom of this alteration since it occurs in response to the lack of moisture in the eyes and its consequent symptoms.

Dr. Fernando Goñi, an ophthalmologist at Clínica Alemana, explains that dry eye syndrome is caused by a lack of lubrication or ocular moisture due to the low production of tears or the alteration in its composition.

There are a wide variety of causes of dry eye syndrome. Environmental factors such as extremely dry and heated air, exposure to smoky or polluted places, aging, and certain systemic diseases are most frequent.

The eyes are constantly covered by a thin layer of tears, made up of three layers – one of the lipids, one liquid, and finally, one of mucin. A change in the amount and composition of any of them can cause this syndrome.

For example, an insufficient amount of oily substance in tears will cause the middle water layer to evaporate too quickly. On the other hand, if there is insufficient water, the tears will not be able to fulfill their function adequately. Also, a decrease in mucinous substance will prevent tears from spreading evenly over the surface of the eye.

Eyelid problems or diseases that alter the composition or distribution of the tear also cause dry eyes. Certain medications such as birth control pills and antidepressants, among others, can cause this syndrome; wearing contact lenses can exacerbate the problem.

Some diseases cause dry eyes, such as Sjögren’s syndrome, which is related to systemic diseases such as Rheumatoid Arthritis and Lupus.

Lastly, many of the causes tend to produce more noticeable results as people age. As a consequence, older adults are more prone to dry eye problems. Decreased tear production, also known as Sicca Keratoconjunctivitis, is a common age-related cause of this syndrome. This is usually more common in women due to hormonal changes as a result of menopause.

Dr. Goñi explains that the diagnosis is suspected based on the data provided by the patient about the symptoms. ‘We confirmed this with a clinical ophthalmological examination, in which tear secretion is measured with the Schirmer test, which consists of placing small strips of special paper on the eyes for a few minutes to see how much they get wet. That gives an idea of ​​how the patient’s tear is. ‘