Botox in the management of epiphora and dry eye
Epiphora is the term for a watering eye. It causes many troubling symptoms for the patient, including blurring of vision, periocular irritation and social embarrassment.
There are a variety of causes of epiphora, this article will focus on the causes that can be treated with botulinum toxin A (BTX-A). The lacrimal gland is innervated by cholinergic nerve fibres. BTX-A injection into the lacrimal gland prevents the release of acetylcholine, a neurotransmitter which then prevents neurotransmission and decreases tear production. The onset of action is one week and the duration of action is 3-6 months. Repeated injections are thought to cause disuse atrophy which allows for longer intervals between injections.
Injection of Botox into the lacrimal gland has been successful in a variety of causes of epiphora. Its use is off-label so informed consent is required.
1) Nasolacrimal duct obstruction. Dacryocystorhinostomy is the gold standard for management of this condition. BTX-A is considered in patients in whom surgery is contraindicated and in elderly patients that cannot have a general anaesthetic.
2) Punctual and canalicular obstruction. A Jones tube is the surgical option for patients with these conditions. Active ocular allergy is a risk factor for failure of this procedure, BTX-A is therefore a useful option. It is also a consideration in elderly patients.
3) Functional epiphora. These patients have patent system, no ocular irritation or lid malposition. BTX-A is an effective treatment in these patients.
4) Crocodile tears. Surgical management of this condition has had poor outcomes. An improvement in symptoms in these patients after BTX-A injection has been found.
Concentration and dosage
There are two forms of botulinum toxin A that can be used for lacrimal injection: Abobotulinumtoxin A (Botox) and onabotulinumA (Dysport). Dysport requires a two-fold dose of botox. Dilution is performed with 0.9% sterile saline. Botox is commonly diluted with 2 ml to give a concentration of 50units/ml. The most common starting dose is 2.5IU, increasing the dose doesn’t increase the duration. Higher doses may be required for the desired effect.
Intraglandular injection technique
The injection is given in an out-patient setting. A transconjunctival injection is given into the palpebral portion of the lacrimal gland. This is done under direct visualisation and so enables a lower dose. The procedure is performed using a 30 gauge needle. The patient is asked to look inferomedially. This approach is thought to be safer because the gland is visualised. A transcutaneous injection is given into the orbital part of the gland.
The literature shows mixed results with 70-87% of patients having a complete resolution of the epiphora. Some show partial improvement and some show no improvement at all. There were no differences between children and adults in their response to treatment. It is thought that 2.5IU is an adequate dose and that higher doses were not associated with any further benefit. Results showed that most patients required repeat injections after four months.
Well-known side effects like ecchymosis, headache, rash and flu-like symptoms may occur.
Complications specific to the area include ptosis, haemorrhage and strabismus. Ptosis occurs in approximately 13% patients but was transient and resolves about a month after injection. Higher incidences of ptosis have been reported with lower concentrations and higher volumes of the toxin. This is due to diffusion with an increased risk of affecting the surrounding muscles. Ocular dryness has not been reported in patients who have received the injection. The one exception is in patients with crocodile tears. These patients can also have orbicularis muscle synkinesis, the toxin may therefore exacerbate an exposure keratopathy.
Botulinum toxin in the treatment of dry eye secondary to a decrease in tear production:
BTX –A can also be used in dry eye and blepharospasm. It decreases the action of the lacrimal pump and blinking by injecting it into the orbicularis oculi muscle fibres that act on the canaliculi. In dry eye it can be injected into the medial part of the upper and lower lids along the medial canthal tendon from a point near the punctum. In the lower lid it causes a reduction of the horizontal movement of blinking and in the upper lid, the vertical movement. The dose is 2.5IU. These injections are considered an alternative to punctal occlusion.
Botulinum toxin causes a decrease in tear production resulting in dry eye:
Botox for crow’s feet or lateral canthal rhytids, can cause dry eye. This is thought to occur due to diffusion of the toxin into the lacrimal gland which causes decreased tear production. BTX-A works on the parasympathetic terminals therefore also causing a reduction in secretion from the meibomium glands.