Dry eye syndrome
Dry eye syndrome describes the state in which tears are not produced or retained for sufficient time to keep the eyes lubricated
Posted: 28 April 2016
If you’ve missed yesterday’s episode of this week’s feature on allergic conjunctivitis, click here.
Writer: Asha Fowells
Allergic conjunctivitis and dry eye caused by hay fever can cause major discomfort for patients during the summer months.
Keratoconjunctivitis sicca is the term used to describe the state in which tears are not produced or retained for sufficient time to keep the eyes lubricated – hence the more commonly used name “dry eye syndrome”. The production of tears is quite a complex process, being under both nervous and hormonal control and reliant on good functioning of the lacrimal glands to produce the aqueous components, the Meibomian glands to produce the lipids that fulfil an important hydrophobic function, and the conjunctival goblet cells to produce the mucins that coat the cornea and facilitate even distribution of the tear film. Also vital are the lacrimal ducts and eyelids, and the lacrimal canaliculi at the inner corners of the eyelids that connect to the lacrimal sac and onto the nasolacrimal duct, which drains into the nasal cavity.
Dry eye syndrome may arise because of a reduction in tear production, for example as can occur in conditions affecting the skin around the eyes such as rosacea or blepharitis, or increased evaporation of tears, which may occur in low humidity environments such as those created by central heating or air conditioning, or as the consequence of a low blink rate caused by prolonged use of a computer or microscope or in high winds. Adverse drug reactions and allergic conjunctivitis can cause not only a drop in tear production but also a rise in evaporation of the reduced quantity that is produced.
Less common causes of dry eye syndrome include lagophthalmos, an inability to fully cover the eyelids when blinking (such as can occur in hyperthyroidism), Sjögren’s syndrome which can occur as a result of a connective tissue disorder, dehydration, Bell’s palsy, as a complication of contact lens use or because of low dietary omega-3 fatty acid intake. The condition is common, with prevalance increasing with age, and affects more women than men.
The typical symptoms include a feeling of dryness, grittiness or soreness in both eyes, which may be worse on waking or deteriorate as the day progresses. Patients often complain that their eyes are more prone to watering than they are used to, particularly if it is windy, and say their sight temporarily blurs but clears when they blink. In some cases, conjunctivitis or ulceration of the cornea are the presenting symptoms, both of which are complications of the condition.
In the majority of patients, a diagnosis of keratoconjunctivitis sicca can be made on symptoms alone by a GP. However, there are some individuals who will require referral to an optometrist or ophthalmologist in order that they can confirm the opinion or run some tests that help inform management. These investigations are likely to include examination of the surface of the eye and tear quality using a slit lamp, and may also involve assessment of tear film break up time using fluorescein drops, or the Schirmer test which provides an evaluation of tear quantity.
Join us tomorrow for the last episode of this week’s feature on allergic conjunctivitis as we’ll be talking about treatments