Dry Eyes: Causes and Remedies

Background

The tear film is the outermost connection between the surface of the eye and the environment and is involved in the visual process. It moisturizes, protects and nourishes the eye. It is an aqueous gel containing water, mucins, salts, antibacterial proteins and antibodies, vitamin A, and lipids, among other substances, and is distributed over the eye during blinking. It is formed by the lacrimal glands (tear fluid), the conjunctiva and cornea (mucins), and the meibomian glands of the eyelids (lipids). The lacrimal secretion enters the nasal cavity via the lacrimal puncta and the lacrimal ducts.

Symptoms

Dry eye is a multifactorial disease of the lacrimal fluid and ocular surface. Possible symptoms include:

• Sensation of dryness, sandiness and foreign body.
• Pain
• Irritation, burning or stinging eyes
• Sensitivity to light, itching
• Increased blinking
• Fatigue
• Visual disturbances
• Inflammatory processes and redness

Paradoxical eye watering is also possible. Dry eyes can worsen the quality of life and limit personal and professional activities. They are a risk factor for other eye diseases.

Causes

Any dysfunction of the structures involved in tear film formation can lead to dry eyes. The two main causes include, first, a deficiency of tear fluid and, second, factors that promote evaporation of fluid from the ocular surface (Table 1). For example, occlusion of the lacrimal duct inhibits secretion of lacrimal fluid. A large eyelid opening and infrequent blinking lead to increased evaporation of fluid from the ocular surface. A number of environmental factors can trigger or worsen the condition. Ocular dryness is characterized by increased tear film osmolarity and tear film instability. It damages the epithelial cells and makes them susceptible to infections. Inflammation, in particular, is now considered an important factor and a cause of dry eye. Table 1. causes of dry eyes (based on Report of the International Dry Eye Workshop, 2007) 1. tear fluid deficiency:

• Sjögren’s syndrome is an autoimmune disease in which, among other things, the lacrimal glands are destroyed.
• Tear deficiency, often age-related, heredity, AIDS, sarcoidosis.
• Occlusion of the lacrimal duct, e.g. scarring eye diseases, chemical and thermal burns.
• Reflex blockage, e.g., surgical procedures, contact lenses, diabetes, herpes.
• Medicines

2. evaporation:

• Diseases of the meimom gland, e.g. skin diseases such as rosacea.
• Disorders of the opening of the eyelids
• Low eyelid blink rate, e.g., in Parkinson’s disease.
• Drugs, e.g. isotretinoin
• Vitamin A deficiency
• Preservatives in eye products, e.g. benzalkonium chloride.
• Wearing contact lenses
• Diseases of the ocular surface, such as allergic conjunctivitis.

3. environmental factors:

• Infrequent blinking and a large eyelid opening increase evaporative loss, for example, computer work, work at the microscope, gamer, television.
• Natural aging
• Low androgen and high estrogen concentrations are risk factors.
• Medications: Antihistamines, anticholinergics, beta blockers, diuretics, some psychotropic drugs, antiandrogens, estrogens, amiodarone.
• Low humidity, dry and cold air, heated homes in winter, high wind speed, occupational environment (eg, office workstation, air conditioning, screen work), air pollution, air travel.

Diagnosis

The diagnosis is made by the ophthalmologist based on the medical history and with various tests. Other eye diseases can cause similar symptoms and should be excluded.

Nonpharmacologic treatment

If possible, the causes or risk factors should be influenced. Meibomian gland function can be improved with heat treatment and good lid margin hygiene. So-called punctum plugs (punctual plugs) are small, permanent or degradable plugs that block the tear points, inhibiting the outflow of lacrimal secretions. Finally, sealed eyeglasses and therapeutic contact lenses, among others, are also used.Various surgical methods are available. A watch glass dressing is applied when there is a lack of closure of the eyelids, such as fascial palsy.

Drug treatment

Tear substitutes:

• Are eye drops or eye gels that moisten and lubricate the eye. Substances used include viscosity-increasing agents such as povidone, hyaluronic acid, hypromellose, carbomers, polyvinyl alcohol, carmellose, dextranes, macrogols, and salts. They may contain pharmaceutical agents such as dexpanthenol or vitamin A. The ophthalmic agents are placed in the conjunctival sac of the affected eye several times a day. Treatment is purely symptomatic and not curative. Products without preservatives should always be preferred. In particular, the common benzalkonium chloride can cause adverse effects on the eye (e.g., eye irritation, corneal inflammation). Less toxic preservatives and those that dissolve on the eye are available.

Eye ointments:

• Contain substances and active ingredients such as thin kerosene, petrolatum, lanolin and dexpanthenol. They are designed to stabilize the physiological lipid layer of the tear film and protect against evaporation. A strand of ointment is inserted into the conjunctival sac. Possible adverse effects include hypersensitivity reactions (lanolin). They are used less frequently than artificial tears, but have a stronger moisturizing effect.

Eye sprays:

• Contain, among other things, phospholipids and are sprayed on the eyelid (and not in the eye!). Thus, they get like the natural lipids on the edge of the eyelid and should thus stabilize the lipid layer of the tear film.

Vitamin A eye ointments:

• Contain vitamin A retinol palmitate, which counteracts keratinization on the eye. They are approved for the additional treatment of dry eye. The ointment is placed in the lower conjunctival sac. Possible adverse effects include visual disturbances immediately after administration.

Anti-inflammatory agents:

• Are effective against the inflammatory processes that can contribute to dry eye. Ciclosporin eye drops were approved in many countries in 2016. Ciclosporin is immunosuppressive and anti-inflammatory. Glucocorticoid eye drops and oral omega-3 fatty acids are also effective against inflammation. Glucocorticoids can cause ocular side effects, especially with prolonged use.
• Lifitegrast (Xiidra) is an anti-inflammatory agent in the LFA-1 antagonist group that was approved in the United States in 2016 and in many countries in 2018. Lifitegrast blocks the interaction between LFA-1 on T cells and ICAM-1 on endothelial cells, thereby inhibiting T cell extravasation, migration, and proliferation, as well as the release of proinflammatory cytokines.

Secretion-promoting agents (secretagogues):

• Increase the formation or secretion of the natural components of the eye film, and thus should allow a more causal treatment. These include, for example, diaquafosol tetrasodium (INS365, Prolacria), a P2Y2 receptor agonist. Phase III clinical trials have been completed, but the compound has not yet been approved by the FDA. Other candidates include 15-(S)-HETE, ecabet sodium, rebamipide, and androgens. The cholinergic pilocarpine (Salagen) and cevimelin (not commercially available in many countries) in tablet form are also used to treat dry eye resulting from Sjörgen syndrome. Pilocaprine has previously been approved in many countries for the treatment of dry mouth in patients with Sjögren’s syndrome, but not for this indication.

Eyebright eye drops:

• Are common means in alternative medicine. They contain eyebright tincture or eyebright in some cases deep homeopathic potentization (D3). The application originally goes back to the theory of signatures: the flower of the plant resembles an eye with eyelashes.

Finally, antibiotics (eg, tetracyclines for rosacea, blepharitis), autologous serum, numerous alternative medicine therapeutics and other agents are used. Vasoconstrictive agents such as tetryzoline should not be used in our view. They increase dryness and may cause adverse effects.