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Dry Eye (in Facial Palsy)
Individuals with Facial Palsy frequently encounter problems with the affected eye being dry.
This is caused by lack of tear production in the affected eye, causing a dry, possibly painful eye, with risk of corneal ulceration.
In Facial Nerve palsy there are 2 problems which contribute towards making the eye dry:
1. The greater petrosal nerve, derived from the facial nerve, supplies the parasympathetic autonomic component of the lacrimal gland. - controlling production of moisture/tearing in eyes.
2. The zygomatic branch of the Facial Nerve supplies Orbicularis Oculi, and the resulting paralysis causes inability (or reduced ability) to close the eye or blink, so the tears (or indeed artificial lubrication in the form of drops, gel or ointment) are not spread across the cornea properly.
The following efffects may be observed:
- The widening of the distance between the upper and lower eyelids, technically described as a "widened palpebral fissure".
- The loss of blink reflex and inability to close the eyelid, due to impaired orbicularis oculi function, can lead to excessive dryness of the cornea, "exposure keratopathy".
- The lower eyelid may turn upwards (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. (The medical term for this is lagophthalmos).
- Dysfunctional lacrimation (abnormal flow of tears); the overflow of tears onto the face (known as epiphora) being further increased by the absence of lower lid nasal twist – as the nasal twist helps pump tears into the lacrimal drainage system.
Ectropion of lower eyelid Corneal ulcer
Symptoms caused by Dry Eye
Symptoms may include:
- 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 short periods of time in an otherwise dry eye
Other factors which can exacerbate Dry Eye
- Age: Dry occur can occur in the elderly even without any damage to the facial nerve
- Medical conditions: Rheumatoid Arthritis, diabetes, Parkinson's Disease and thyroid problems can all cause Dry Eye syndrome. In addition conditions such as seborrhaeic dermatitis and blepharitis can affect the 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, eg. at 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: ie. that it can lead to 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 do have a strong "Bell's Phenomenon" where the eyeball rolls upward. This means that they think the eye is closed, as they no longer see anything out of it, but in 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:
- If they do not have full eye closure then advise them to tape the eye closed overnight, and apply lubrication in the form of Lacri-Lube ointment
- During the day, advise regular use of lubricating drops or gel
- Protect the eye from winds, so 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
A dose of Botulinum Toxin ("Botox") to cause a temporary ptosis (closure) of the eye is sometimes employed in cases of dense facial palsy, when the eye is a high risk of corneal ulceration.
Remember, if your Facial Palsy patient is in the 1st few weeks (or even months in some cases) of onset, once the nerve has chance to regrow and respond to your physiotherapeutic interventions the Dry Eye is likely to improve enormously, due to improved eye closure and increased blink activity. Therefore, the following surgical techniques may not be required in these cases.
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 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 2 drainage channels in the eye, resulting in the tears/artificial lubrication staying in the eye for longer, thus increasing moisture