Dry Eye

Original Editor - Wendy Walker.

Top Contributors - Wendy Walker, Kim Jackson, Jess Bell, Rishika Babburu and Naomi O'Reilly

Introduction

Individuals with facial palsy frequently experience dry eye on the affected side. This is caused by lack of tear production in the affected eye, which causes a dry, possibly painful eye, and can lead to corneal ulceration.As can be seen in the photograph, the damage the ulcer inflicts on the cornea can result in blindness in the affected eye:

Corneal ulcer

In facial nerve palsy, there are two factors that contribute to dry eye:

1. The greater petrosal nerve, derived from the facial nerve, supplies the parasympathetic autonomic component of the lacrimal gland, controlling the production of moisture or tearing in eyes
2. The zygomatic branch of the facial nerve supplies orbicularis oculi - in facial palsy, paralysis of this muscle leads to an inability (or reduced ability) to close the eye or blink, so tears (or artificial lubrication in the form of drops, gel or ointment) are not spread across the cornea properly

The following effects may be observed:

• An increased distance between the upper and lower eyelids, technically described as a "widened palpebral fissure"
• The loss of the blink reflex and inability to close the eyelid, which is caused by impaired orbicularis oculi function, can lead to excessive dryness of the cornea (i.e. "exposure keratopathy")
• The lower eyelid may turn outwards (a condition known as paralytic eyelid ectropion)
  • When associated with upper and lower lid retraction, this prevents the eyelids from closing to cover the eye completely (i.e. lagophthalmos)

Ectropion of lower eyelid

Dysfunctional lacrimation (abnormal flow of tears)

• The overflow of tears onto the face (known as epiphora) is further increased by the absence of lower lid nasal twist - normally the nasal twist helps to pump tears into the lacrimal drainage system

Symptoms

Symptoms may include:

• A gritty, burning or scratchy feeling in the eye
• Redness of the eye
• Feeling of dryness in the eye
• Pain in the eye
• Blurred vision
• Frequent eye infections
• Corneal damage
• Excessive watering of the eye - confusingly, this can occur for periods of time in an otherwise dry eye

Other Factors Which Can Exacerbate Dry Eye

• Age
  • Dry eye occur can occur in the elderly even without any damage to the facial nerve
• Medical  conditions
  • Rheumatoid arthritis, diabetes, Parkinson's, Sjögren's syndrome and thyroid problems can all cause dry eye syndrome
  • In addition conditions such as seborrhaeic dermatitis and blepharitis can affect tear production and exacerbate dry eye
• Medications
  • Antihypertensives, antihistamines and antidepressants can all reduce tear production
• Gender
  • Women can be more susceptible to dry eye syndrome due to hormonal changes, such as menopause, during pregnancy or when taking oral or injected contraception

Management of Dry Eye

It is important to stress to the patient the risks of dry eye in facial palsy - i.e. that it can lead to the formation of a corneal ulcer, which in turn can cause loss of vision in the affected eye. Any facial palsy patient with an acutely red and sore eye should attend their local eye hospital or local A & E as soon as possible.

It is also essential to establish whether the eye is closing fully at night. Often the patient reports that it is, as they are "in the dark" when they close their eyes. But this does NOT mean that they have full eye closure - often they have little or no eye closure, but have a strong "Bell's Phenomenon" where the eyeball rolls upward.

This means that they think their eye is closed, as they no longer see anything out of it. But in actual fact, there is incomplete closure and the white of the eye is clearly visible to the clinician. The easiest way to convince the patient that they need to tape their eye closed at night is to take a photograph of the eye in what they think is complete closure.

Below is a photograph of Bell's Phenomenon:

Advice

• If patients do not have full eye closure, advise them to tape the eye closed overnight, and apply lubrication in the form of an ointment/gel (ointments last much longer than drops). The drops/ointment should be preservative free.
• During the day, advise regular use of lubricating drops or gel, again these should be preservative free.
• Protect the eye from the wind
  • When walking outside in windy weather, it is helpful to wear wrap-around style sunglasses
• Avoid air conditioning as much as possible
  • Switch off the air-con in the car as this dries out the eye
• Humidifiers can be useful to increase the moisture content of air (in the office or at home)
• Keep hydrated
  • Be sure to drink enough fluid
  • Many authorities recommend a minimum of 6 to 8 glasses per day
• Use of an adhesive weight positioned on the upper eyelid can be an effective way of improving blink and eye closure, thus helping to mitigate some of the effects of dry eye by spreading whatever lubrication is present in the eye (from drops or naturally produced) across the cornea. These removable externally applied weights have also be shown to help reduce synkinesis.
• Occasionally, with a long-lasting and severe dry eye, custom-made" scleral contact lenses" can be used:
  • Scleral lenses are large diameter, rigid, gas permeable lenses
  • They are larger than traditional contact lenses and are dome-shaped
  • The dome sits over and above the cornea, with the edges of the contact lens resting on the sclera (i.e. white of the eye)
  • Scleral lenses trap a reservoir of fluid behind the lens and this fluid protects the cornea

Botulinum Toxin

A dose of Botulinum Toxin ("Botox") is sometimes employed in cases of dense facial palsy to cause a temporary ptosis (closure) of the eye when there is a high risk of corneal ulceration.

Surgical Interventions

Remember, facial palsy patients who are in the first few weeks (or even months for some) of onset, tend to find that dry eye often improves enormously once the nerve has the chance to regrow and they start to respond to physiotherapeutic interventions. This improvement is due to better eye closure and increased blink activity. In such cases, the following surgical techniques may not be required. However, if the person has a chronic, long-term flaccid facial palsy, the following interventions may be indicated:

• Upper eyelid weight implantation
  • A small weight (usually made of gold or platinum) is placed into the upper eyelid
  • When the person automatically blinks the paralysed eye, the weight helps it to close
• Tarsorraphy
  • The corner (usually the lateral corner) of the eye is stitched together, thus narrowing the palpebral fissure
• Lateral canthoplasty
  • This procedure shortens the muscle and tendon at the outer corner of the eyelid, preventing the lower eyelid falling away from the eye
• Punctal Plugs
  • Tiny silicone plugs are inserted into one or both of the two drainage channels in the eye, meaning that tears / artificial lubrication can stay in the eye for longer, thus increasing moisture