Introduction

Think about how eyesight connects you to just about everything you experience; be it recognising someone you love, watching a beautiful sunset or wetting your appetite before eating. So imagine when your vision is impaired or lost, it's not just your eyesight that suffers, but it is something that ripples through different aspects of your life. It is therefore important that you do all you can to protect your eyes and also that you have information on what to do and how to cope if your eyes are injured and your vision is impaired.

This article will explore a specific condition that affects the eyes -- exposure keratoconjunctivitis, its symptoms, how to manage it and how to prevent it.

Definition of keratoconjunctivitis

Keratoconjunctivitis is a collective term which refers to inflammatory conditions¹ that affect the outside layers of the eye, the superficial cornea and the conjunctiva. These conditions that affect the eyes have many causes, some of which include viral, bacterial, autoimmune, and toxic causes or can be brought about by allergens.^1,2 

What is exposure keratoconjunctivitis (EKC)?

Exposure keratoconjunctivitis (EKC), also called exposure keratitis, happens when the cornea is injured from dryness caused when a person's unable to close their eyelids completely. In the majority of cases, EKC is a manageable and treatable condition.³

Anatomy and physiology of eyelid function

Normal eyelid mechanics & importance of eyelid closure

Without our eyelids, our eyes would be very dry as well exposed to many harmful things in the environment. Blinking helps coat our eyes with a tear film. This tear film is made up of three layers: lipid, aqueous and mucin, which work together to protect and lubricate the eye. The lipid layer, which is the outermost layer, stops the evaporation of the layer beneath, stopping overproduction of tear film over the eyelid as well as functioning as a lubricant for the eyelid. The aqueous, middle layer works to give the eye its nutrients,⁴ while the inner mucin layer functions as a protection mechanism, washing off any debris from the cornea and lubricating the eye.⁵ When we blink or close our eyes, we enable the eye to carry out these functions; otherwise, without this mechanism, our eyes would be dry and prone to injury. 

Tear film and corneal protection

The tear film is important because it protects the eye and helps maintain good vision. It is as essential that the eye produces tears as it is that the tears are able to evaporate. This balance is what contributes to a good vision and the protection of the eye.⁶ In EKC, the tear film’s aqueous, lipid, and mucin layers are not working as they should, therefore damaging the eye.

Incomplete eyelid closure (lagophthalmos)

Lagophthalmos happens when our eyelids are unable to fully close.^5,7 When a person is unable to blink or close their eyelids completely, this leads to EKC. The most common cause of lagophthalmos is weakness or paralysis of the facial muscles (facial paralysis).^8,9

Other factors that can put a person at risk of developing this inability to close one’s eyelids are as follows: 

Neurological conditions

Neurological conditions like Bell’s Palsy can lead to EKC. When a person has Bell’s Palsy, their facial muscles are affected, making it more difficult to move their eyes properly.  As a result, there is incomplete closure of the eyelid, leading to EKC if untreated.¹⁰

Reduction in muscle tone 

This is more often seen in patients who are sedated or in a coma.⁸ A study of twenty-six patients in the ICU at Manchester Royal Infirmary revealed that about half of the patients given muscle relaxants or placed under deep sedation developed lagophthalmos. The study showed that the more lagophthalmos a patient experienced, the worse the damage was to the surface of their eyes.¹¹ The risk of exposure keratoconjunctivitis is even more prevalent in older ICU patients.⁷ 

Anaesthesia  

Going under the knife has its risks. More than 50 per cent of patient, when under anaesthesia, are unable to close their eyes completely. As a result, the eyes are vulnerable to injury from objects or things in the environment. In addition, general anaesthesia causes eye dryness because it reduces the production of the eye’s tear film.⁵ Research has also shown that the risk for patients' inability to shut their eyes fully while under general anaesthesia is made worse by eyelash extensions.¹²

Mechanical trauma & burns 

Anything that stops the eyelid from closing properly leads to drying out of the eye. Injuries like burns on the eyelid or eyelid surgery may cause improper eyelid function.^3,8 Trauma from objects outside the eye or surgical instruments in an operating room can also damage the surface of the eye.¹³

Increased skin tightness 

Skin conditions that restrict the proper movement of the eyelids,  like eczema, that cause the skin around the eyes to be tighter than normal, can also lead to lagophthalmos.⁸ Tumours that push the eyeball forward, making it impossible for the eyelids to close,³ can also cause lagophthalmos. 

Corneal damage

Corneal damage is any harm or injury affecting the outer layer of the eye. Patients with this level of injury to their eyes are advised to see a specialist as soon as possible, as untreated symptoms can lead to serious visual impairment.³ It must also be noted that experiencing recurring EKC can disrupt the healing process of the eye, further damaging the eye and increasing the risk of bacterial or viral infections.¹ Damage to the surface of the eye can be through factors such as:

• Mechanical abrasions 
• Chemical injuries¹
• Infections 
• Improper wearing of contact lenses

Clinical features

Symptoms

• Eye dryness,
• Irritation
• Redness 
• Foreign body sensation 
• Blurred vision
• Photophobia 
• Excessive tearing/dryness¹⁴ 

In more severe cases, patient may experience difficulty closing their eyes, sharp pain or mucopurulent discharge (a white-ish or yellow discharge containing mucus and pus).^3,14 

Diagnosis

In order to find out whether or not you are suffering from EKC, a doctor will have to examine your symptoms thoroughly. This involves a physical examination, such as the eyelid closure test,^3,1 taking into account your medical history, using advanced imaging tools that can look into the eye and, where necessary, laboratory tests to examine tear production.¹ The eye may also be assessed for sensitivity, and fluorescein staining of the eye can be carried out to check for infection or scarring in more severe cases.³

Management

The goal of EKC treatment is to protect the cornea and keep it lubricated. The exact treatment is dependent on the underlying cause of the EKC; in some situations, relieving symptoms like irritation and discomfort is the primary focus, while in the long term, more permanent treatment methods that restore eye health can be used. Based on this, treatment options may include:

• Artificial tears work to reduce symptoms by maintaining moisture on the eye's surface
• Lubricant oils⁹
• Taping 
• Surgical intervention, reconstruction procedures of the eyelid, in some cases, are needed. The severity of facial paralysis, age and health are normally taken into account before considering surgery⁹

New and innovative medical treatments are being developed, including biologics, autologous serum, regenerative treatments and stem cell therapy.¹ When fully established, these treatments can help manage EKC, possibly with more efficacy. 

Prevention and prognosis

There are several preventative measures for EKC. You can reduce the risk of developing EKC by doing the following:

• Modifying your environment, for example, wearing protective eyewear, so as to reduce exposure to allergens or alien objects that may cause drying of the eyes or cornea injury, which leads to lagophthalmos
• Monitoring, regular eye exams, particularly for high-risk populations such as individuals with Bell palsy or chronic dry eye, regular check-ups can help detect early signs of the condition
• Surgical prevention can be done at the early stages of lagophthalmos rather than waiting for the symptoms to progress until intervening. Some studies have shown this has more potential to provide favourable outcomes⁷ 
• For those who wear artificial lashes, removing them before undergoing any surgery can be very beneficial
• Proper hygiene can also help as it reduces the risk of developing any disease that may lead to lagophthalmos¹

Summary

Exposure keratoconjunctivitis is a condition that affects the eyes when our eyelids do not fully close, either when blinking or when sleeping. The eyelid protects our eyes from foreign objects, lubricates our eyes and helps clean our eyes using tears. EKC is commonly seen in patients with facial paralysis and amongst ICU patients because of the nature of their conditions; these groups of patients are more likely to be unable to fully shut their eyes; therefore are more prone to developing EKC from their eyes being exposed for long periods of time. Treatment of EKC is based on the underlying cause of the disease; therefore, management strategies may differ from person to person, also considering the severity of the patient’s condition. New treatments which can better manage EKC are being developed; however, more research and awareness of this topic are needed to help people living with EKC.