Dry Eyes

Synonyms: Keratoconjunctivitis sicca, Xerophthalmia (used for dry eye associated with vitamin A deficiency)

Tears are a complex solution of proteins, salts, lipids and mucins. These play a hydrating, immunological, nourishing and lubricating role. Some of the components are simply there to allow the tears to remain on the corneal surface effectively and the tear/cornea interface has important refractive properties. The tears are produced under nervous and hormonal control by various glands within the eyelids and adjacent to the globe, the biggest of which is the lacrimal gland. Each type is responsible for producing a different combination of the components essential to good tear maintenance. The lids are equally important in distributing the tears across the corneal surface.

Dry eyes can arise as a result of insufficient tear production or excess tear loss. Underlying conditions are summarised below:¹

This is a common condition affecting up to a third of over 65 year olds. It is 50% more common in women than in men.

Symptoms

• Gritty irritation and foreign body sensation
• Burning or pain, aggravated by air conditioning, prolonged reading or computer work, dry air etc
• Stringy mucus discharge
• Transient blurring of vision

Symptoms tend to be worse towards the end of the day. Less often, there may be itching, photophobia and a tired or heavy feeling. Some patients may report a lack of emotional tears or may have noticed a less vigorous response when peeling onions. They rarely complain of a dry eye until the diagnosis is made and they then relate their symptoms to 'dry eye'. Some patients paradoxically complain of too much tearing - a excessive reflex response to corneal dryness.¹

Signs

• Non-corneal signs:¹ look for a decreased meniscus and a reduced tear break-up time (see diagnosis below). There may be a mucous discharge and strands of mucin on the corneal surface.
• Corneal signs: there may be signs of keratopathy such as punctate epithelial erosions, filament and plaque depositions on the cornea. When severe, frank ulceration, leading to perforation, can occur. Dry eyes are predisposed to bacterial infections.

Assessment³

• The dry eye: how bad is it, to what extent is it interfering with the person's life and is it threatening the cornea?
• Is there any other explanation for these symptoms and signs (see differential diagnosis below)?
• Could there be an underlying cause for the dry eye (see above list)?
• What treatment has already been tried by the patient?
• Ask about aggravating or risk factors and explore how these could be reduced if at all.

You can generally gauge the severity of the problem from the patient's account. However, if you are not sure (the understated or over anxious patient), a helpful guide to quantifying the disease is the Ocular Surface Disease Index, a questionnaire providing a scale for the answers given to questions about symptoms. See further reading for a copy of the questionnaire.

Diagnosis can be confirmed by assessing tear break-up time or carrying out the Schirmer test.

Tear break-up time

This simple test needs the use of a slit-lamp, set on a bright light setting with a cobalt blue filter.

1. Instill fluorescein into the lower fornix.
2. Ask the patient to blink several times and then stop.
3. Measure the time between the last blink and the first appearance of a dark spot on the cornea (formation of a dry area).

A tear break-up time of less than 10 seconds suggests a dry eye.

Schirmer test

1. Instil a drop of local anaesthetic.
2. Prepare a filter paper (5mm x 35mm with folded end).
3. Gently dry the eye.
4. Apply the filter paper with the folded end hooked onto the lower lid margin at the junction between the middle and outer third (take care not to touch the cornea).
5. Tell patient to keep eye open and blink normally.
6. Measure the amount of wetting after 5 minutes: 13-15mm wetting rules out a dry eye. 6-10mm is borderline and less than 6mm indicates dry eye.

• Other causes of Red Eye - see our dedicated record. Dry eyes tends to be a bilateral condition, even if one eye is more affected than the other.
• Blepharitis - this often co-exists with a degree of dry eye.
• Blocked nasolacrimal duct - this can cause tears to overflow and therefore inefficiently coat the cornea so causing a paradoxical dry eye.
• Floppy eyelid syndrome - overweight male patients with floppy and easily everted upper eyelids associated with chronic papillary conjunctivitis of the upper palpebral conjunctiva.

• Ease discomfort
• Protect and preserve the cornea
• Treat any underlying conditions

1. Explain the protracted nature of this condition and the importance of the patient's input in managing it.³
2. Many of these patients suffer with concurrent blepharitis and good lid hygiene measures can go someway towards alleviating both problems.
3. Discuss aggravating and risk factors (another opportunity to address the issue of smoking cessation). Regular computer breaks, use of room humidifiers and minimising contact lens wear will all help.³
4. Rule out underlying causes including medication (e.g. beta-blockers) and over the counter drugs (e.g. anti-histamines).¹

Now you can focus on the tear issue:

• Preserve existing tears by minimising tear evaporation (e.g. suggest avoiding central heating, room humidifiers).
• Tear substitutes:
  • Most common approach in the primary care setting.
  • Drops, gels and ointments are available both over the counter and on prescription.

If things do not settle, consider referral (see above) for further management:

• Reduction of tear drainage:
  • Temporary: the canaliculi openings can be occluded by the placement of small mushroom-shaped collagen punctual plugs. This is done in the clinic setting with a slit lamp and only requires local anaesthetic drops.
  • Permanent: this is considered in severe cases and involves either instillation of permanent silicone-based punctal plugs or cautery of the draining canaliculi. Occasionally, the lids are partially surgically sutured together (tarsorrhaphy) in order to reduce the palpebral aperture and hence the surface area from which tears can evaporate.
  • Other: lid abnormalities connected with excessive tear drainage (such as ectropion) are to be corrected. Special contact lenses can be used to help maintain a tear film on the corneal surface and some advise patients who have lagophthalmos to sleep with swimming goggles.
• Drug treatment:
  • Mucolytic agents such as acetylcysteine 5% drops may be helpful in dispelling sticky residual mucus, applied 3-4 times daily.⁴
  • Oral cholinergic agents such as pilocarpine stimulate tear secretions and may be used where there are systemic causes such as patients with Sjögren's syndrome. Other tear stimulants include diquafosol and rebamipide (topical agents) and oral cevilemine.
  • Cyclosporin A reduces cell-mediated inflammation of the lacrimal tissue.
  • Topical corticosteroids have been shown to have some beneficial effect and research is being carried out into the role of tetracyclines and biological tear substitutes.
  • There is research being carried out into the use of androgens.¹

A new approach involves salivary gland autotransplantation: transplantation of oral mucosa containing submandibular salivary glands to reconstruct the fornix (the junction between the posterior eyelid and the eyeball). However, this would be a very long way down the treatment line.

• Drops:
  • Examples - hypromellose (most commonly used), normal saline (useful 'comfort' drops in contact lens wearers), polyvinyl alcohol, sodium hyaluronate, povidone.
  • Action - increase wettability and retention time.
  • Application - usually 3-4 times daily but can be used up to hourly as required. Advise patients to discontinue contact lens wear during treatment. If this is impossible, use preservative-free drops and allow 30 minutes after drop application before putting in contact lens.
  • Over the counter preparations - all of the above available.
  • Additional notes - hypromellose / acetylcysteine 5% combination preparation is available. Choose drops rather than ointments if other eye drops are required. Beware of development of preservative sensitivity in prolonged or frequent use (> 6 times a day) of drops; use preservative-free drops.
• Gels:
  • Examples - variety of carbomers e.g. Viscotears®, GelTears®, Luiquivisc®.
  • Action - help form a stable tear film.
  • Application - 3-4 times a day: they cling to the surface of the eye and hence need less frequent applications than drops.
  • Over the counter preparations - all of the above available.
  • Additional information - not for use in children and pregnant / breast-feeding patients.⁶
• Ointments:
  • Examples - liquid paraffin, yellow soft paraffin.
  • Action - reduce evaporation of tears by coating cornea.
  • Application - best applied at night as they can cause blurred vision due to coating effect on cornea. Contact lens wear contra-indicated. Particularly useful in more severe cases of dry eye and in cases of recurrent corneal erosions.
  • Over the counter preparations - all of the above available.

Dry eyes are more susceptible to infections. These may be superficial, e.g. conjunctivitis. However, if the dry eye is severe, corneal complications (infection, ulceration and rarely, perforation).

There is little formal research into the natural history of the condition but it tends to follow a protracted course although with little associated morbidity when treatment is adhered to. The prognosis depends on the underlying cause if there is one.