Keratoconjunctivitis Sicca (KCS), also known as “dry eye,” is a common ophthalmic condition in dogs and cats that affects the ocular surface, specifically the cornea and conjunctiva.

This disease results from the deficiency of some of the phases of the tear film, which leads to tear hyperosmolarity and, consequently, a series of ocular complications that can compromise the visual health of the animal.

The structure of the tear

To better understand KCS, it is important to know the three layers that make up the tear film and their functions:

• Mucinous layer: This layer, the innermost, modifies the surface tension of the tear so that it adheres and distributes properly over the surface of the eye. Mucin is produced and secreted mainly in conjunctival goblet cells.
• Aqueous layer: The intermediate layer, and the most abundant, hydrates the ocular surface and transports nutrients and oxygen essential for the metabolism of the cornea. It also acts as a flushing mechanism to remove debris and foreign bodies. This watery portion is produced and secreted in the main and accessory lacrimal glands.
  
• Lipid layer: The outermost layer protects the aqueous layer from evaporation, allowing the tear to remain in the eye longer. In addition, it increases the surface tension of the tear, preventing overflow over the edge of the eyelid and lubricating the eyelids. This layer is produced and secreted mainly in the meibomian glands.

KCS classification

The KCS can be classified into two main types:

• Qualitative KCS: It is produced by a pathological decrease in the lipid or mucoid components of the tear film, which makes it difficult for it to remain on the cornea, either due to excess evaporation or difficulty adhering. It is usually due to damage or inflammation in the meibomian glands or goblet cells of the conjunctiva.
  
• Quantitative KCS: It is produced by a pathological decrease in the aqueous component of the tear film. It can have various causes, the most common being localized and chronic immune-mediated inflammation of the lacrimal gland. This is the most common form of KCS, and in most cases it progresses to a mixed form (quantitative and qualitative) over time.

What symptoms does it cause?

Symptoms of KCS may include mucosal exudate, conjunctival hyperemia, corneal opacity, neovascularization, corneal edema, and ulceration, among others. The diagnosis of KCS requires a thorough evaluation of the patient’s medical history and specific ophthalmological tests, such as the Schirmer Test, Fluorescein Test, and the Lysamine Green Test.

What treatment is used?

Treatment of KCS may include artificial tears, topical immunosuppressants, and surgical treatments, depending on the severity and underlying cause of the disease. Additionally, supplementation with specific nutraceuticals such as LACRIMALIS+ can help manage this disease, offering natural help to maintain pets’ eye health.

If your pet presents symptoms compatible with this disease, go to your trusted veterinarian for correct diagnosis and treatment.