What is dry eye syndrome?
This is when the eye becomes dry and/or inflamed and uncomfortable due to tear deficiency or excessive tear evaporation. Most cases of dry eye are mild and easily treated. However this condition can often cause significant distress; it can cause transient vision problems; and it can occasionally be associated with more serious underlying medical conditions. Very rarely, dry eye can be so severe as to cause permanent damage to the front of the eye.
What are the types of dry eye disorder?
Dry eye can be classified into two types
- Aqueous tear deficiency, where the lacrimal glands make too few tears. This is occasionally part of an auto-immune condition known as Sjogren’s syndrome, and this can be linked to systemic diseases like rheumatoid arthritis.
- Evaporative dry eye, where the oil layer on top of the tear film is either deficient (leading to rapid evaporation of the tear film) or composed of abnormal fatty acids that contribute to inflammation. This is often associated with meibomian gland dysfunction, where the eyelid’s oil glands become inflamed and/or blocked by abnormally thick secretions (meibum).
The below video shows abnormally thick meibum being expressed from the meibomian glands in cases of meibomian gland dysfunction. This can cause evaporative dry eye signs and symptoms.
Who is most at risk of getting dry eye?
Dry eye is more likely to affect women, and it also becomes more prevalent as we get older. Hormonal changes can increase the likelihood of dry eye, for example thyroid conditions and also changes during the menopause, while on hormonal contraception or during pregnancy.
Can dry eye and watery eye exist at the same time?
Yes, this is a common paradox which is often confusing for patients who have dry feeling eyes but occasionally note very watery eyes too. Normal wetting of the ocular surface keeps the cornea moist at all times. In dry eye, the cornea is allowed to dry out briefly, but this stimulates a dry eye feeling which causes reflex secretion of lots of tears. This often happens to patients outdoors, and in reality it often co-exists with some reduction in the tear drainage capacity of the lacrimal system.
Why does using a computer make my eyes feel dry?
This is almost certainly because when people concentrate on a computer screen, they tend to blink less often, so allowing more evaporation of tears.
What treatments are available?
Simple measures include staying well-hydrated, limiting caffeine intake, and avoiding make-up on or directly adjacent to the eyelid margin. Indoors, if central heating is causing the air to dry out, a humidifer may help. Outdoors, if sudden gusts of wind cause lots of dry eye sensation (sometimes followed by reflex watering) then some wrap-around sunglasses could mitigate this.
For aqueous tear deficiency, the simplest treatment is lubricating eye drops (artificial tears) of which many different types are available, each with subtle differences in composition, dosing, preservative burden, and method of delivery. More advanced cases of aqueous tear deficiency may benefit from punctal occlusion (either temporary or permanent), where the tear drainage duct is occluded to allow the patient’s own tears to stay on the eye for longer.
Evaporative dry eye is usually associated with meibomian gland dysfunction and an unstable tear film. The mainstay of management is to re-establish normal flow of meibomian gland secretions using a regime of eyelid hygiene (eg. warm compresses) regularly. More advanced cases may benefit from short courses of antibiotics, either in the form of eye drops or tablets.
Some people’s eyes don’t fully close when they are sleeping (lagophthalmos). In these cases, a thicker type of lubricating eye ointment (typically based on liquid paraffin) can often help the eyes to remain moist overnight.
Which are the best artificial tear drops to use?
For patients requiring very frequent lubricant drop application (eg more than 6 times per day), preservative-free drops (eg. hyaluronic acid) are the best choice. They can be used as frequently as desired with no serious side-effects, and they can be used while wearing contact lenses. There are many different brands of this type of drop – most of which are available over the counter without a prescription. The key differences between the different brands relate to the strength of drop, the method of dispensing, and whether the preparation is unit-dose or multi-dose. Your eye surgeon should be able to advise you on particular brands that suit you and your condition best.