Dry Eye Syndrome

Dry eye syndrome occurs due to insufficient tear production or excessive tear evaporation, leading to discomfort and potential damage to the eye’s surface.

STRUCTURE AND FUNCTIONS OF TEARS

The tear film consists of three layers:

1. Mucin layer (innermost) – Produced by surface epithelial cells, it converts the hydrophobic epithelial surface into a hydrophilic one, ensuring the even distribution of the aqueous layer.
2. Aqueous layer (middle) – The largest portion of the tear film, secreted by the lacrimal glands, containing electrolytes (Na, K, Cl), immunoglobulins, and antibacterial proteins like lactoferrin and lysozyme.
3. Lipid layer (outermost) – Produced by the Meibomian glands, it prevents excessive tear evaporation.

Tears serve several critical functions, including:
✔ Providing a smooth optical surface for clear vision
✔ Protecting surface cells from drying and infections
✔ Flushing out foreign substances

TYPES OF DRY EYE

Primary Lacrimal Gland Deficiency (Congenital Dry Eye)

• Extremely rare
• Associated with Riley-Day Syndrome, where abnormal nerve stimulation leads to poor tear production.

Secondary Lacrimal Gland Deficiency

Occurs due to:

• Inflammation of the lacrimal glands (e.g., lymphoma, sarcoidosis, hemochromatosis, amyloidosis)
• HIV infection
• Graft-versus-host disease
• Lacrimal gland surgery or radiation therapy
• Systemic medications that block nerve signals to the lacrimal gland
• Menopause-related androgen imbalance (contrary to popular belief, estrogen reduction is not the main cause)
• LASIK, cataract surgery, or corneal transplants, which may damage the nerves stimulating tear production

Sjögren’s Syndrome

A condition causing dry eye and dry mouth due to immune system dysfunction. It is classified as:

• Primary Sjögren’s (occurs alone)
• Secondary Sjögren’s (occurs with autoimmune diseases like lupus, scleroderma, or polymyositis)

Diagnostic Criteria for Sjögren’s Syndrome:
✔ Schirmer’s test shows reduced tear production
✔ Objective evidence of reduced salivary gland function
✔ Labial salivary gland biopsy confirms inflammation
✔ Presence of autoantibodies (ANA, RF, specific antibodies)

Patients meeting all four criteria are diagnosed with definite Sjögren’s syndrome, while those with three criteria are classified as probable cases.

Evaporative Dry Eye

• Caused by environmental factors (dry air, high heat, high altitude).
• Neurological or mechanical disorders preventing full eyelid closure lead to increased tear evaporation.

Mucin Deficiency

• Results from chemical burns, trachoma, mucous membrane pemphigoid, Stevens-Johnson syndrome, which damage the epithelial cells that produce mucin.

SYMPTOMS OF DRY EYE

🔹 Common complaints include:

• Burning
• Itching
• Stinging
• Dryness
• Eye fatigue
• Light sensitivity
• Redness

🔹 Symptoms worsen in the morning due to:

• Loose eyelids
• Sleeping with eyes partially open
• Eyelid inflammation

🔹 Triggering factors:

• Prolonged screen use
• Airplane cabins
• Air conditioning and heating systems in offices

🔹 Visual disturbances:

• Blurred vision due to an unstable tear film
• Patients with diabetes or nerve damage may not feel dryness despite severe symptoms and should still be evaluated for dry eye.

DIAGNOSTIC METHODS

Staining Tests

• Fluorescein dye test: Highlights damaged epithelial cells.
• Rose Bengal test: Stains dead epithelial cells and provides more detailed analysis than fluorescein.
• Van Bijsterveld test: Assesses corneal and conjunctival staining.

Tear Film Stability

• Tear Break-Up Time (TBUT) Test: Measures the time before the tear film starts breaking down.
  • Less than 5 seconds indicates dry eye.

Tear Production Measurement

• Schirmer’s Test: Measures basal tear secretion using a paper strip placed in the lower eyelid.
  • <5 mm wetting in 5 minutes confirms dry eye.
  • 6-10 mm suggests potential dry eye.
• Phenol Red Thread Test:
  • Uses a thread soaked in phenol red, which changes color when in contact with tears.
  • No need for anesthesia, unlike Schirmer’s Test.

Other Diagnostic Tests

• Lysozyme & Lactoferrin Levels: Assessed using fluorophotometry.
• Osmolarity Testing: Evaluates tear film concentration.
• Corneal Sensitivity Testing: Determines nerve involvement.
• Blood Tests and Minor Salivary Gland Biopsy: Used for Sjögren’s Syndrome diagnosis.

TREATMENT OF DRY EYE

Artificial Tears

✔ Increase tear volume and reduce osmolarity.
✔ Contain viscosity-enhancing agents like methylcellulose, hydroxypropyl methylcellulose, and polyvinyl alcohol.
✔ Preservative-free drops are recommended for severe cases.
✔ Artificial tear ointments provide longer-lasting lubrication.

Stimulation of Tear Production

• Medications that stimulate tear production may be prescribed.
• For severe cases (Schirmer test <2 mm), tear drainage can be blocked:
  • Punctal occlusion using plugs (temporary)
  • Punctal cautery (permanent closure)
  • Prevents tear film from draining too quickly

Environmental and Behavioral Adjustments

• Use humidifiers to combat air conditioning and heating dryness.
• Take breaks from prolonged screen exposure.
• Adjust workstations to prevent excessive strain on the eyes.

Anti-Inflammatory Treatments

• For inflammation-related dry eye, topical and systemic medications can help.
• Eyelid hygiene and warm compresses can improve Meibomian gland function.

CONCLUSION

Dry eye is a multifactorial disease that affects vision and comfort. Early diagnosis and personalized treatment are crucial to prevent complications. From artificial tears to surgical interventions, proper management can significantly improve a patient’s quality of life.