Dry eye syndrome, also known by its official name keratoconjunctivitis sicca (KCS), is an inflammation of the cornea and conjunctiva due to insufficient tear production. The term “kerato” refers to the cornea, “conjunctivae” refers to the conjunctiva, “itis” refers to inflammation, and “sicca” refers to dryness, collectively indicating the clinical symptoms of dry eye syndrome.

Tears are the fluid in the eyes that help lubricate, protect, and nourish the cornea, enabling the eyes to function normally. Tears primarily consist of water, approximately 95%, and also contain other components such as fats (which prevent tear evaporation), mucin (which helps tears adhere to the corneal surface for longer), minerals, and proteins with antibacterial properties.

The main functions of tears are to lubricate the eyes, kill pathogens, and remove foreign substances. Insufficient tear production can lead to irritation because the eyes cannot blink properly, resulting in redness of the conjunctiva, changes in the cornea’s appearance, accumulation of eye discharge, chronic eye inflammation, or corneal ulcers. Severe dry eye, if left untreated, can lead to various eye diseases, both infectious and non-infectious, ultimately leading to vision loss.

Treatment approaches for dry eye syndrome

using medication involve two main groups of drugs: tear stimulants and tear substitutes.

Tear stimulation

  1. Pilocarpine: Stimulates the parasympathetic nervous system, which has connections to the tear glands. However, the use of this medication may have systemic side effects, such as nausea, diarrhea, and bradycardia.
  2. Cyclosporine (CsA): Acts as an immunomodulator, inhibiting the production of interleukin-2, which helps suppress the increase of T-helper and cytotoxic T cells in the tear glands. CsA also has anti-inflammatory properties, reduces the accumulation of pigment granules in the eyes, and controls mucus production in tears.
  3. Tacrolimus : Exhibits similar effects to CsA but with higher potency. It is often used when CsA is ineffective. However, prolonged use of CsA or tacrolimus may lead to corneal squamous cell carcinoma in dogs.

Tear substitutes

  • These substances help lubricate the eyes. Common forms of tear substitutes include solutions, gels, and ointments containing ingredients like artificial tears, cellulose-based solutions/gels, and artificial tears combined with petrolatum, mineral oil, or lanolin.

In addition to the aforementioned tear substitutes, another interesting substance for treating dry eye syndrome is chondroitin sulfate. This substance belongs to the glycosaminoglycans group and has significant potential as a tear substitute. Chondroitin sulfate ophthalmic solution, containing 20% chondroitin sulfate, is effective for both dogs and cats in treating dry eye syndrome and corneal inflammation. It can also be used for eye cleaning and during surgeries, making it a valuable clinical eye medication.

ภาพ A : แสดง Chondroitin Sulfate พบบริเวณ Extracellular Matrix

Studies have shown that chondroitin sulfate helps restore corneal surface integrity more rapidly than sodium hyaluronate. It also reduces inflammation effectively due to its NF-kappa B inhibitory properties, which are related to the inflammatory process in the eyes. Furthermore, chondroitin sulfate’s Newtonian fluid properties enable it to adhere well to the glycocalyx layer surrounding corneal cells, ensuring tear stability and consistency on the corneal surface.

In clinical use, chondroitin sulfate ophthalmic solution has demonstrated positive results in treating dry eye syndrome, and its anti-inflammatory effects, effects on corneal surface changes, tear quality and stability, have been compared favorably to sodium hyaluronate eye drops in dogs with dry eye.


ภาพ B : แสดงการลดการอักเสบโดย Chondroitin Sulfate (CS)

ภาพ C : แสดงกราฟ คุณสมบัติในการลด Shear stress และ shear rate ของ Newtonian fluid และ Pseudoplastic fluid



  1. Ashwarth S, Harrington J, Hammond GM et al., 2021. Chondroitin sulfate as a potential Modulator of the stem cell niche in cornea. Front Cell Dev Biol. 8: 567358.
  2. Ledbetter EC. Munger RJ, Ring RD et al. 2006. Efficacy of two chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects and ulcerative keratitis associated with bullous keratopathy in dogs. Vet Ophthalmol. 9: 77 – 87.
  3. Wang X, Majumdar S, Ma G et al., 2017. Chondroitin sulfate – based biocompatible crosslinker restores corneal mechanics and collagen alignment. Invest Ophthalmol Vis Sci. 58: 3887 – 3895.
  4. Wouk F, Castanho L, Kleiner JA et al., 2021. Comparison of the anti-inflammatory effects, epithelial morphofunctional changes, tear quality and stability using chondroitin sulfate (CS) and sodium hyaluronate (HA) eyedrops in dogs with dry eye. https://wsava2021.com/wp content/uploads/sites/48/2021/11/WSAVA21-Abstracts-Nov-15-by-topic.pdf.

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