Dry eye syndrome is also known as keratoconjunctivitis sicca or dysfunctional tear syndrome. It is a common condition mainly affecting older adults, with about one third of people over 65 years being affected.
For most patients it is a mild, benign condition, but it can be associated with a risk of serious sequelae in a minority of cases, which need ophthalmological assessment.
In dry eye syndrome there is either decreased production of aqueous tear (aqueous tear deficiency) or excessive evaporation of tears (evaporative tear dysfunction) or a combination of both.
The most common cause of dry eye is insufficient tear production (aqueous tear deficiency). There are numerous causes of aqueous tear deficiency and the most common ones are subdivided into non-Sjogren and Sjogren.
Non-Sjogren causes are: idiopathic, age-related, lacrimal gland disease, vitamin A deficiency, chemical and thermal burns to the eye, medications - including antihistamines, beta-blockers, anticholinergics, oral contraceptives, chemotherapy and diuretics and radiation therapy. Loss of reflex tearing due to damage to ocular surface nerves from contact lens wear, diabetic neuropathy, herpetic disease, topical and systemic anaesthesia, fifth cranial nerve disease and corneal surgery may also be a cause.
Sjogren's syndrome could be primary or secondary (for example, rheumatoid arthritis).
Evaporative tear dysfunction may be associated with meibomian gland disease, which reduces the production of lipid layer of the tear film, low blink-rate, from Parkinson's disease for example, ocular surface disease and disorders of eyelids, such as proptosis, lid palsy and ectropion.
Most commonly, dry eyes are associated with a history of persistent eye irritation, itching and/or intermittent blurred vision. Patients can also present with local burning sensation, foreign body sensation, corneal ulcer (photophobia, pain, redness and loss of visual acuity), stringy mucus discharge and excessive tears due to a reflex response to the dry cornea.
There are some features in the history which can help diagnose the cause of dry eyes. Symptoms that get worse in low humidity environments, such as air conditioning and central heating, towards the end of the day, in wind and after a long duration of reading, driving, watching television or computer use are likely to be caused by aqueous tear deficiency.
However, if the patient complains of symptoms being worse on waking then the underlying cause is likely to be evaporative tear dysfunction.
Other symptoms, such as dysphagia, dry mouth and vaginal dryness, are suggestive of Sjogren's syndrome.
Ask about the duration, onset and severity of the symptoms. This is important as sudden onset with severe symptoms warrant urgent referral to an ophthalmologist. Enquire about the impact these symptoms have on quality of life and assess the risk factors outlined in the box.
Consider whether the patient's medications could be the cause of dry eyes. Try to exclude other differential diagnosis, such as allergy or hay fever, infected conjunctivitis, keratitis, iritis, acute glaucoma and episcleritis.
Enquire if the patient has tried eye drops or OTC remedies. This is important because some eye drops have preservatives which actually make the situation worse. Lastly, check patient's previous medical, surgical and ocular history.
Mild cases can be diagnosed in primary care on history and examination, with a trial of first-line treatment and early review. However, where symptoms are more severe, examination using ophthalmic tools, such as the slit lamp, is indicated. For this, GPs can ask patients to see an optometrist, but if there is concern about serious sequelae, such as corneal damage, urgent referral to an ophthalmologist is indicated.
Common investigations that are used to confirm diagnosis of dry eyes are tear film break-up time and Schirmer's test.
Dry eye is not a curable condition. The main aim of the treatment is to keep patients symptom free. Most patients can be managed in primary care with patient education and tear substitutes.
Patient education includes explaining the nature of the disease, advice about avoidance of aggravating factors, including medications. GP should also emphasise the importance of good compliance with tear-replacement therapy.
In mild cases, standard artificial tears, such as cellulose derivatives or carbomers, should be prescribed. Paraffin-based eye ointment can also be used at bedtime. For moderate disease, the ophthalmologist may recommend:
- Preservative-free artificial tears to reduce epithelium toxicity.
- Physiological tear substitutes, such as hyaluronic acid, to help in the healing process of the ocular epithelium.
- Acetylcysteine 5% if there are visible strands of mucus.
- Topical anti-inflammatory drops, such as corticosteroids or ciclosporin.
- Non-medical treatment involves lower punctum occlusion by a plug either intracanalicular or punctal, to stop the drainage of tear.
Severe cases are normally dealt with in secondary care and treatment entails secretagogues and specialised surgical procedure.
Consider referral to an ophthalmologist if there is no relief of symptoms despite appropriate treatment for four weeks; deterioration of visual acuity; if corneal damage is suspected; if an underlying causative disease, such as Sjogren's syndrome, is suspected and if the patient is less than 40 years of age.
Organise urgent same day referral if there is an acute loss of vision or if you suspect acute glaucoma, keratitis or iritis.
- Dr Malik is a F2 trainee and Dr Sim is a GP in Bedfordshire