Botulinum Toxin in Primary Eye Care
Botulinum toxin can be beneficial in patients with neuro-ophthalmic and ophthalmic indications, according to a presentation by James L. Fanelli, OD, FAAO, Cape Fear Eye Institute, Wilmington, NC at the 2019 Optometry’s Meeting.
Botulinum toxin works by blocking the release of neurotransmitter acetylcholine from axon endings at the neuromuscular junction. It is produced by Clostridium botulinum and can be broken down into 8 different neurotoxins. Type A is used commercially and medically in products such as Botox, Dysport, and Xeomin.
Botox comes in 50 or 100 units of botulinum toxin and is reconstituted with sterile, nonpreserved 0.9% NaCl. It must be refrigerated. Its duration of action can last between 3 and 6 months. Dysport comes in 500-unit vials, is stored at room temperature, and, according to Dr. Fanelli, has a similar clinical effect as Botox if a 4x greater dose is used. Xeomin is a unit-to-unit equivalent with Botox, can be stored at room temperature, and has no additives.
Cosmetic applications include use in glabellar folds, which require two injections in each corrugator and one in the procerus, lateral periocular rhytids, central forehead wrinkles, perioral lipstick lines, and platysmal bands in the neck.
For localized injections, patients should frown and relax. The injection should be made in the adjacent muscle as opposed to the crease line. Injections should be made 1 cm above the bony supraorbital ridge so the resting tone of muscle can be reduced and the epidermis and dermis remodeled.
Contraindications include infection; pregnancy/lactation; ALS, Lambert-Eaton, or myasthenia gravis; aminoglycosides or antimalarials; and egg allergy.
Dr. Fanelli noted that 5% of those treated develop antibodies. Increasing time between injections, minimizing dose, and changing neurotoxins can help lessen the likelihood of developing antibodies.
Strong candidates for treatment include those with stubborn headaches; noncompliance with oral medications; contraindications to and/or adverse events from standard prevention; and coexisting jaw, head, or neck muscle spasms. Patient preference is also taken into consideration.
Neuro-Ophthalmic Application
Botulinum toxin can be used in dystonias that are involuntarily sustained or spasmodic-patterned repetitive muscle contractions, including Meige syndrome, benign essential blepharospasm, Brueghel syndrome, segmental cranial dystonia, and hemifacial spasm.
Meige syndrome is an idiopathic orofacial dystonia of benign essential blepharospasm with lower facial involvement. It is characterized by lip pursing, tongue protrusion, and trismus. Speech is impacted.
Benign essential blepharospasm is neurochemical and characterized by bilateral eyelid spasms. The condition is more common in women and the mean age of those affected is 56 years. It is worsened by stress, fatigue, and glare, and improved with sleep. The functional incapacitation of benign essential blepharospasm is 12%.
Brueghel syndrome is an idiopathic oromandibular dystonia of benign essential blepharospasm with lower facial, mandibular, and cervical involvement. It is characterized by a widely opened mouth and jaw contractions.
Segmental cranial dystonia involves several cranial nerves affecting the eyes, mouth, jaw, and tongue.
Finally, hemifacial spasm is a disorder in which muscles are innervated by facial nerves. It presents unilaterally and is more common in middle-aged women. In addition to injections of botulinum toxin, treatment for hemifacial spasm includes microvascular compression, a neurosurgical procedure that relieves pressure from the impacted cranial nerve. Microvascular compression, also called the Jannetta procedure, has an approximate 80% cure rate.
Additional neuro-ophthalmic applications include oculomotor synkinesis, acquired nystagmus, and spasm of near reflex.
Ophthalmic Uses
There are several ophthalmic uses for Botox injections.
Protective ptosis can be induced with Botox in cases of corneal compromise secondary to cranial nerve V or cranial nerve VII palsies, as well as in cases of upper lid retraction in Graves’ disease. Reversal of spastic inwardly turning lower lid can also be done with Botox.
In patients with strabismus, intramuscular injection can be used. Dr. Fanelli explained, “Use in one muscle (eg, MR) will result in increased contractility of contralateral muscle (eg, LR), resulting in more alignment of the eyes after recovery of the injected muscle.”
Injections can also be used in patients with ameliorating aberrant nerve regeneration problems, including Bells Palsy-induced facial muscle aberrations and aberrant regeneration to the lacrimal gland resulting in excessive lacrimation.
Botox can be used to reduce post-herpetic neuralgia by blocking the release of acetylcholine for neuromuscular transmission and the release of nociceptive neuropeptides involved in chronic inflammatory pain response. It can also be used to reduce tension across scars, making it a viable option for patients with surgical facial wounds.
Complications
Dr. Fanelli explained that complications from Botox are usually the result of poor injection technique or excessive dosing, and can result in ptosis, reduced blink reflex, strabismus, lagophthalmos, ecchymosis, and drooling.
He concluded, “Proper injection technique varies for the location of the injection and into what regions it is being applied and for what conditions.”
Reference:
Fanelli JL, Skorin L Jr. The clinical use of Botulinum toxin in primary eye care. Presented at: Optometry’s Meeting; June 19-23, 2019; St. Louis, MO.
