The dreaded dry eye

Ocular surface disease cycle

The ocular surface requires a constant supply of healthy tear film to maintain its clarity and defence.  

 A healthy tear film consists of 3 layers:

1. A thick aqueous layer to nourish ocular surface structure
2. A mucus layer to maintain the aqueous layer on the hydrophobic ocular surface structures
3. An oil layer produced by meibomian glands at the lid margin to reduce evaporation of the aqueous surface

These layers of tear film need to be spread across the ocular surface by eyelids to maintain a healthy ocular surface.

The cycle of dry eye often starts with a disruption or decrease of aqueous production (due to age, medical and ocular history, lifestyle factors, lid positioning, ptosis or poor blinking). The mucus and oil production then get increased as compensatory mechanism causing further unbalance of the tear film and mucus discharge or blepharitis/meibomian gland overproduction. The poor-quality unstable tear then leads to inadequate wetting of the ocular surface and subsequent inflammation and breakdown of corneal and conjunctival epithelial cells. This process further destroys aqueous production and the cycle perpetuates.

Causes of dry eye

Dry eye disease is common, and ageing is often the main cause of decreased aqueous production. Up to a third of people aged 65 or older have this condition, and women are often affected most. Factors that cause instability in aqueous production or delivery can trigger dry eye disease; the following list is not exhaustive:

• Blepharitis and meibomian gland dysfunctions.
• Lifestyle and work patterns. Prolonged near work and excessive screen time reduce our blink rate and can exacerbate dry eye symptoms.
• Poor sleep, diet and high stress may disrupt meibomian gland function leading to low quality or an unstable tear film.
• Environmental factors, i.e. prolong work in air-conditioned environments or dry surroundings can exacerbate existing dry eye symptoms. For example, in professions such as flight attendants, low humidity and air pressure may worsen eye dryness.
• Contact lenses. While modern contact lenses have improved immensely on oxygenation in general, overwearing or their long-term wear can cause micro injuries on the cornea as well as subacute irritation and inflammation that impacts the quality, quantity and spread of the natural tear.
• Previous eye surgeries, including laser refractive procedures.
• Allergic eye diseases.
• Systemic conditions such as thyroid dysfunction, diabetes, menopause, polycystic ovarian syndrome (PCOS).
• Autoimmune diseases such as Sjögren syndrome, rheumatoid arthritis (RA), lupus can all increase risk factors for dry eye disease. Although having dry eyes does not necessarily indicate an underlying autoimmune condition, it is worth checking for an autoimmunity if dry eye symptoms are refractory to conventional treatment.
• Skin conditions such as eczema and rosacea may be associated with ocular manifestations, leading to dry eye symptoms.
• History of chemotherapy, immunosuppressants, cytotoxic therapy - these treatments can induce or exacerbate ocular surface disorders and reduce tear production by directly acting against accessory lacrimal glands, the primary producers of background tears.
• Latrogenic causes such as some cosmetic procedures that can affect lid margins (lash extensions, use of prostaglandin containing mascaras for lash growth) or induce poor/inadequate blink or lid closure (ptosis repair, blepharoplasties, botox) can also contribute to eye dryness by inducing exposure.
• Prolonged use of ‘eye brightening’ drops which works by inducing vasoconstriction of surface blood vessels have been reported to cause irreversible damage and permanent dry eye symptoms.
• Skin whitening products can cause direct corneal damage that mimic dry eye symptoms at early stages.
• Unbalanced diet lacking in omega-3 may also be contributory.

Dry eye symptoms

Common presenting complaints include pain, gritty sensation, and ironically watery discharge in the form of reflex tearing, sticky eyelids, and blurred vision. The symptoms may occur episodically, they can be worse in the morning or evening or triggered by factors like reading, cold weather or exposure to outdoor elements.

Treatment options

The treatment of dry eye disease and associated lid margin pathology requires substantial time and effort from the patient and thus it’s essential to educate them on the importance of consistent actions addressing different areas of their life. Patient can be reassured that while this is a troublesome condition, it is almost never blinding.

Treatment plans are tailored for individual patients depending on the subtype of their dry eye disease. However, often all 3 target areas need to be tackled simultaneously.

1. Replenish and restore tear quantity and quality: trial and identify lubricant of choice and apply regularly. In principle, hyaluronic based eye drops replenish, and Trehalose eye drops supplement the lipid layer.
2. Improve lid margin health performing regular lid hygiene: warm compresses and target lid margin cleaning with wetted cotton bud or specialised lid margin wipes.
3. Implement patient lifestyle changes to improve their sleep, diet and reduce screen use.

Treatments such as topical Azithromycin eye drops BD for day 1,2,3 per week for 4 weeks and/or oral Doxycycline tablets 100mg orally for 3 months can be useful to treat lid margin disease, especially if patient has a background of severe blepharitis or rosacea.

For patients with busy lives or those unable to do the eyelid cleaning activities at home, optometrists can offer lid cleaning service with mechanical methods, automated heat mask massager and IPL (Intense Pulse Light) therapy to target meibomian glands to improve their function.

Systemic investigation including anaemia, thyroid function and autoimmune screening (if supported by other symptoms in patient’s medical history) should be considered in patients who are not responding to conservative dry eye treatment. It’s worth noting that perimenopause or menopause women can present with dry eyes as primary symptoms of their hormonal changes.

When to refer to ophthalmology

Normally, patients have good results with conservative dry eye treatment at home and in primary care, but sometimes a specialist ophthalmic support is needed. Cases where we recommend a referral to secondary care include:

• When a patient has been stuck in the ocular surface disease cycle for a long time with established inflammation that needs topical steroids, or immunosuppressant (Cyclosporine drops).
• The dry eye symptoms are secondary to a lid issue - positioning or dermatological issues i.e. eczema/ dermatitis/rosacea.
• If a patient has developed a stye (hordeolum or chalazion) that is refractory to conservative treatment and oral antibiotics (>2-3 weeks).
• A recurrent stye in the same spot, or a ‘bald’ stye where there is a disruption to lid margin or eyelash loss that needs a second opinion, for suspected malignancy such as Basal Cell Carcinoma (BCC).
• Where there is a need for extra support for patient education.
• Any concerns that the symptoms may not be associated with dry eye disease: uniocular conjunctivitis, unusual prolonged or severe redness, reduction in visual acuity or 1 line worse than their usual baseline, a suspected infection (in contact lens wearers a sudden red eye is an infection until proven otherwise), a new onset of extreme light sensitivity (i.e. patient is wearing sunglasses in your practice) or pain that requires oral pain killers.
• Suspected rare conjunctival autoimmune or malignancy conditions such as pemphigoid or Squamous Cell Carcinoma (SCC).