Botox in Ophthalmology
-
Upload
laxmi-eye-institute -
Category
Healthcare
-
view
801 -
download
0
description
Transcript of Botox in Ophthalmology
Botox in ophthalmology
Presenter: Dr Vikram S
NakhateModerator: Dr Preeti Joshi
Botulinum neurotoxinThere are seven distinct strains of
Clostridium botulinum that have been identified.
Each of these different strains is characterized by the type of botulinum neurotoxin they are capable of producing and have been classified as type A, B, C1, D, E, F, and G.
Botulinum toxin type A is felt to exert the most powerful neuromuscular blockade and is also capable of exerting its effect for the longest duration of time.
Botulinum toxin type A and type B are composed of a 150-kDA polypeptide consisting of a light chain and heavy chain joined by a disulfide bond ( Fig. 12-18-1 ).
While the heavy chain is responsible for binding to the nerve terminal receptors, the light chain exerts its effect by preventing the release of acetylcholine from the nerve terminal
Mechanism of action
The light chain exerts paralytic effect of botulinum toxin by inactivating group of proteins that are responsible for fusion of vesicles containing Ach with the nerve cell membrane
This group of proteins are referred as SNARE complex(soluble N-ethylmalemide-
sensitive factor attachment protein receptor)Inhibition of Ach release results in localised
muscle weakness that gradually reverses over time
Approximately 2 mths after administration of botulinum toxin,new nerve terminal sprouts emerge,and extend towards the muscle surface
Once one of the new sprouts forms a physical synaptic connection with the previous NM junc,the motor nerve unit is re-established
Commercially availableBotulinum toxin type A is commercially
available as two preparations: Botox (Allergan Inc, Irvine, CA) ( Worldwide) Dysport (Ipsen Pharmaceuticals, France).
(European Union )
Botulinum toxin type B Myobloc (Élan Pharmaceuticals, South San
Francisco, CA). (United States)
Clinical applicationsEyelid:Facial dystonia-blepharospasmHemifacial spasmReduce lid retraction- thyroid eye diseaseApraxia of lid openingInduce ptosis in exposure keratopathyLower lid spastic entropion
Strabismus:Infantile esotropia/acquired esotropiaIntermittent exotropia
Nerve palsiesThyroid eye disease related strabismusCongenital nystagmus
Cosmetic:Glabellar linesCrow’s feet
Others:Chronic dry eyeLacrimal hypersecretionPain relief in acute angle closure glaucoma
Eyelids Blepharospasm:Is a focal dystonia characterized by recurrent
involuntary contraction of the orbicularis oculi muscles leading to frequent blinking or forceful eyelid closure
Hemifacial spasmHemifacial spasm (HFS) is characterized by
unilateral irregular clonic or tonic movements of muscles innervated by cranial nerve VII.
The condition is believed to result from vascular compression of the facial nerve at its root exit zone, leading to irritation of the nerve and causing the innervated muscles to contract involuntarily.
inject 2.5 units of BoNT-A (BOTOX) into the orbicularis oculi in the medial and lateral upper eyelids and 12.5 units in the lateral canthus. Lower facial spasms are treated with 2.5 to 5 units in the malar region.
Induce ptosis/Reduce lid retractionBotox can be used to chemically denervate
the eyelids to induce ptosisHas a therapeutic indication in management
of lid retraction in thyroid eye disease, neurotropic keratopathy or bell’s palsy to improve eyelid closure in order to protect cornea
Apraxia of lid openingInability to raise the upper eyelid in the
absence of levator muscle injury , paralysis or orbicularis oculi muscle contraction
Described in isolation or in association with other extrapyramidal disorders like Parkinson syndrome & progressive supranuclear gaze palsy
Btx-A injection into the pretarsal orbicularis oculi allows the levator action to resume and has some beneficial effect on eyelid opening in this subset of patients
Entropion Lower lid entropion may arise due to spastic
contraction of the pretarsal orbicularis oculi muscle
This can propogate a vicious cycle of ocular irritation and further lid spasticity
Injection of 5-10 units of Btx-A into the pretarsal or preseptal orbicularis muscle can eliminate the spastic component of the entropion
Strabismus When an extremely small quantity of Botox is
injected into an eye muscle that is pulling the eye out of position, the drug causes temporary weakness in this muscle for some weeks.
This usually causes a large overcorrection of the strabismus.
During this time the opposite muscle pulls the eye across and tightens while the paralysed muscle is stretched.
This weakening, stretching and tightening process may result in a more balanced position of the affected eye when the paralysis wears off.
< 2.5 u to 5 u injectedStabilize eye with forcep - slide needle along
muscle orbital surface - muscle on stretch initially - then some contraction to give EMG signal. Inject when signal heard
Retrobulbar botoxThe "ideal" patient for retrobulbar Botox has
restricted movement, oscillopsia, and is willing to use only one eye.
Botox can be injected in the retrobulbar space for oscillopsia - rare indication - treat one eye only.
In most cases, patient will have systemic problem such as brain stem stroke.
Complications Ptosis - always transientInduced deviations - usually transientDiplopia - transientLip droop - very bothersome; may be
persistentDilated pupil - rareReduced accommodation - rareScleral perforation - rare - potentially serious
Cosmetic useThe cosmetic use of botulinum toxin is well-
studied for the treatment of glabellar frown lines, horizontal forehead rhytids, and lateral canthal lines (crow’s feet).
Currently, physicians are beginning to explore other uses in the face, such as contouring of the jawline, the neck, and the nasolabial fold.
Glabellar frown lines
Glabellar frown lines are the most common reason for cosmetic injection of botulinum toxin
Facial rhytides and folds in this area result from action of the depressor muscles.
The corrugator superciliaris, medial orbital portion of the orbicularis oculi, and more horizontally oriented fibers of the depressor supercilii produce the vertical lines of the glabella.
The corrugator muscle is a brow adductor moving the eyebrow downward and medially.
It arises from the nasal bone just above the rim of the orbit medially and extends laterally and upward, inserting in the skin above the middle of the eyebrow.
It lies deep to the frontalis, procerus, and orbicularis oculi muscles.
The vertically oriented procerus muscle, which originates from the upper nasal cartilage and the lower nasal bone, produces the horizontal lines of the glabella and nasal root.
It inserts into the skin between the brows and the frontal belly of the occipitofrontalis.
Its fibers interdigitate with those of the orbicularis, frontalis, and corrugator muscles.
A glabellar "spread test" may be performed prior to injection by spreading the glabellar wrinkles apart with the thumb and index fingers.
This may allow an estimate of the expected benefit from botox injections.
Patients with thick sebaceous skin and deep dermal scarring that are not improved with manual spreading usually respond poorly to botulinum toxin injections.
One site on each side is used to inject the corrugator, one site on each side is used to inject the orbicularis oculi and depressor supercilii, and one site is used to inject the procerus in the mid line.
The patient is asked initially to frown and scowl, and the target muscles are palpated.
The first injection is placed into the belly of the corrugator muscle.
The needle is inserted at the origin of the corrugator fibers just above the medial canthus and superciliary arch until bone is felt, and then withdraw it slightly.
The needle is then advanced within the belly of the muscle upward and lateral as far as the medial third of the eyebrow, 1 cm superior to the orbital rim. 4-6 units are injected as the needle is withdrawn.
The next site is approximately 1 cm above the upper medial aspect of the supraorbital ridge. The needle is advanced slightly in a vertical direction toward the hairline. 4-6 units are injected into the orbicularis oculi and depressor supercilii as the needle is withdrawn.
The last injection is central into the belly of the procerus to eliminate the horizontal lines at the root of the nose.
4-6 units are injected at a point where 2 lines drawn at 45° from the medial aspect of the eyebrows converge in the center of the nasal root, just superior to the horizontal plane of the medial canthi.
To avoid resultant accentuation of eyebrow arching in men, an additional 4-6 units are injected 1 cm above the supraorbital prominence vertical to the mid point of the eyebrow.
Complication The most common
complication in treatment of the glabellar complex is ptosis of the upper eyelid.
This is caused by diffusion of the toxin through the orbital septum, where it affects the levator palpebrae muscle.
Precautions To avoid ptosis, injections should not
cross the midpupillary line, and should be 1 cm above the eyebrow.
Digital pressure at the border of the supraorbital ridge while injecting the corrugator also reduces the potential for extravasation.
Patients often are instructed to remain in an upright position for 3-4 hours following injection and to avoid manual manipulation of the area.
Active contraction of the muscles under treatment may increase the uptake of toxin and decrease its diffusion.
Horizontal Forehead Lines
Performing botulinum toxin injections to treat horizontal forehead lines is relatively easy, and the result usually is quite satisfying.
Treatment can be combined with injections for glabellar frown lines when appropriate.
The frontalis muscle elevates the eyebrows and the skin of the forehead.
The fibers of the frontalis are oriented vertically, and wrinkles of the forehead are oriented horizontally.
The medial fibers usually are more fibrous than the lateral fibers, thus requiring less toxin for paralysis.
Total paralysis of the frontalis should be avoided, since this is likely to cause brow ptosis and loss of expression.
Injection too close to the lateral eyebrow can cause lateral eyebrow ptosis.
Multiple injections of small amounts of toxin create weakness without total paralysis.
3-5 sites on each side of the mid line are injected, usually using 2 units (1-3 U) per site.
Sites are separated by 1-2 cm. The initial injection site is approximately 1
cm above the eyebrow directly above the medial canthus.
Additional sites diverge laterally and upward to the hairline in a "V" configuration, often for a total of 3 sites.
Additional sites can be added in the mid line or more laterally depending on individual and clinical response.
Injections of the upper face and periocular region usually are performed with the patient seated, and the patient is asked to remain upright for 2-3 hours to prevent spread of toxin through the orbital septum.
Complication The most significant complication of treatment of
the frontalis is brow ptosis. Injections in the forehead should always be above
the lowest fold produced when the subject is asked to elevate their forehead (frontalis).
If the patient has a low eyebrow, treatment of the forehead lines should be avoided, or limited to that portion of the forehead 4.0 cm or more above the brow.
An equally esthetically unfavorable outcome is the brow that assumes a quizzical or “cockeyed” appearance.
This occurs when the lateral fibers of the frontalis muscle have not been appropriately injected.
The central brow then becomes lowered and the lateral brow is still able to contract and is pulled upward. sides of the brow.
The treatment is to inject a small amount of botox into the fibers of the lateral forehead that are pulling upward.
However, only a small amount of Botox is required, as overcompensation can cause hooded brow that partially covers the eye.
Lateral Canthal Lines (crow’s feet)Aging and photodamage cause much of the
wrinkling in this area. However, the component of hyperfunctional
contraction of the lateral aspect of the orbicularis oculi is targeted for improvement with botulinum toxin injections.
The lateral fibers of the orbicularis oculi are arranged in a circular pattern around the eye. Contraction of these fibers produces wrinkles that extend radially from the region of the lateral canthus.
3 or 4 subcutaneous injections are applied approximately 1 cm lateral to the lateral orbital rim using 2-3 units per injection site (for a total of 6-12 U per side).
Sites are spaced 0.5-1 cm apart in a vertical line or slightly curving arch. Doses that are too high or injections that are too medial can lead to eyelid ptosis or diplopia.
Complication The most common reported complications
in the “crow’s feet” area are bruising, diplopia, ectropion and an asymmetric smile due to injection of zygomaticus major.
If severe lower lid weakness occurs, an exposure keratitis may result.
Precautions These complications are avoided by
injecting at least 1 cm outside the bony orbit or 1.5 cm lateral to the lateral canthus, not injecting medial to a vertical line through the lateral canthus and not injecting close to the inferior margin of the zygoma.
Violating these boundaries has on occasion also resulted in diplopia due to medial migration of Botox and resultant paralysis of the lateral rectus muscle.
Other usesLacrimal hypersecretion:Aberrant regeneration of 7 th cranial nerve
can present with a condition called gustatory epiphora or crocodile tears( excessive lacrimation with salivary stimulation)
Injection of 2.5-5 units of Btx-A into the palpebral lobe of the lacrimal gland can result in a reduction of tear production and symptomatic relief
Effect lasts upto 3-4 mths
Chronic dry eye:Dry eye is due to imbalance in the
composition of the aqueous,mucin and lipid layers of tear film
The drainage system consists of the lacrimal pump and its mech of action is regulated by the orbicularis oculi during blinking
In blepharospasm or hemifacial spasm a chronic dry eye state may result due to excessive blinking
Btx-A injection is administered into the medial portion of the upper and lower eyelids to minimise the lacrimal pump action ,thus allowing the tears to pool in the fornix and provide symptomatic relief
Novel application of Btx-A is its use to relieve periorbital pain after an acute angle closure attack
However, this application has to be viewed and applied with caution as botulinum toxin inhibits acetylcholine release which can result in pupil mydriasis
Conclusion Botulinum injections have become widely
popular for combating the effects of aging. Aging patients will continue to seek out the
procedure. Knowledge of optimal treatment patterns and
adverse effects will allow physicians to safely and effectively deliver this therapy.