Management of strabismus

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Management of strabismus
Specialty ophthalmology

The management of strabismus may include the use of drugs or surgery to correct the strabismus. Agents used include paralytic agents such as botox used on extraocular muscles, [1] topical autonomic nervous system agents to alter the refractive index in the eyes, and agents that act in the central nervous system to correct amblyopia. [2]

Contents

Strabismus is a misalignment of the eyes and may also result in amblyopia (lazy eye) or impairments of binocular vision.

Medication

Pharmacologic injection treatments can be given to cooperative adults under local anesthesia in an outpatient setting, and for some agents, under light general anesthesia. [3] [4] [ unreliable medical source ] In the former case, it is possible to bring the injection needle to an optimal location in the desired muscle using EMG guidance [5] [ unreliable medical source ] as the alert patient looks in diagnostic directions, the needle is advanced until the electromyogram (the electrical signal from an activated skeletal muscle) indicates it is optimally positioned, whereupon the injection is completed. Some agents (e.g., botulinum toxin) can be injected at the insertional end of a muscle under visual guidance, using special forceps [6] [ unreliable medical source ] and allowed to diffuse posteriorly, whereas others (e.g., bupivacaine) must be distributed throughout the body of the muscle, [7] [ unreliable medical source ] which requires non-visual guidance. EMG guidance generally provides more effective injections, but is only suitable for alert, cooperative adults. Because injection treatment does not result in the scarring that is often a troublesome consequence of conventional strabismus surgery, if therapeutic goals are not achieved with one injection, additional injections or surgical treatments can readily be given. [8] [9]

Replacement of strabismus surgery with less invasive procedures began in Alan B Scott's San Francisco lab with his development of botulinum toxin injection treatment. [10]

Some forms of strabismus can be corrected by weakening an extraocular muscle. Botulinum toxin blocks the neuromuscular transmission and thus paralyzes injected muscles. [11] [12] [13] Paralysis is temporary, and it might seem that injections would always need to be repeated, except that muscles adapt to the lengths at which they are chronically held, so that a paralyzed muscle tends to get stretched-out by its antagonist and grows longer by addition of serial sarcomeres (the contractile units of skeletal muscles), while the antagonist tends to grow shorter by deletion of sarcomeres, [14] [ unreliable medical source ] thereby maintaining re-alignment when the toxin-caused paralysis has resolved. If there is good binocular vision, once muscular imbalance is sufficiently reduced, the brain mechanism of motor fusion (which points the eyes to a target visible to both) can stabilize eye alignment. [15] [ unreliable medical source ]

Botulinum A toxin (introduced as Oculinum), now called Botox, is the principal drug used to temporarily paralyze extraocular muscles, and is widely accepted as an alternative to surgery for many types of strabismus. [16] [1] Crotoxin, a snake neurotoxin, is being developed in Belo Horizonte, Brazil as a potential alternative. [17] [ unreliable medical source ]

Botulinum toxin

Botulinum toxin injection is commonly used for small and moderate degrees of infantile esotropia, acquired adult strabismus, and where it is a consequence of retinal detachment surgery, that is, in cases where there is good potential for binocular vision, so that the corrected alignment can be stabilized by motor fusion. Sixth nerve palsy, paralysis of the lateral rectus , the muscle that rotates the eye outwards, is most frequently caused by an ischemic event, from which there is frequently substantial recovery. But during the acute stage of paresis, the lateral rectus is stretched and grows longer, and its antagonist medial rectus shortens. Sixth nerve palsy is treated by injecting the medial rectus muscle, thereby allowing the lateral rectus, paretic though it be, to stretch and lengthen the medial, while it shortens, so that, when the sixth nerve paresis subsides, alignment is improved. The toxin is also useful in other cranial nerve palsies affecting eye muscles. Residual misalignments that remain following traditional strabismus surgery can be corrected with toxin injection. Toxin injections are used for temporary relief during the acute phase of thyroid ophthalmopathy, when misalignments are too unstable to treat surgically. Botulinum toxin has also been used intraoperatively to augment a surgical effect. In complex strabismus cases, toxin can be injected diagnostically as an aid to planning surgical treatment. [3] [1] [18]

The force exerted by a muscle is the sum of its contractile force (“active force”, controlled mostly by neural innervation) and its elastic force (“passive” force, determined stretching). Both are affected by muscle length, which determines the degree of stretch in a given eye position. Botulinum toxin paralysis reduces total muscle force by removing, or reducing, the contractile component. [19]

Botulinum toxin is a neurotoxin present in the cytoplasm of the anaerobic bacterium Clostridium botulinum . It binds presynaptically with high affinity to sites on cholinergic nerve terminals, decreasing release of acetylcholine, thereby blocking neuromuscular transmission, and causing flaccid muscle paralysis. [12] [13] Crotoxin appears to act similarly. [20] [ unreliable medical source ]

To weaken an eye muscle, 1 to 12 units (a few nanograms) of toxin are injected directly into it. The treated muscle weakens over 48–72 hours and remains paretic (partially paralyzed) for 2–4 months, at which time muscle length changes and motor fusion can stabilize the re-alignment. [1]

Complications

Subconjunctival hemorrhage, ptosis (drooping eyelid) and vertical strabismus are the most common complications, most resolving within several weeks. Ptosis and vertical strabismus are caused by spreading of toxin to adjacent muscles, and their risk decreases with lower doses and more accurate injection techniques. Some overcorrections, such as exotropia (eyes deviated outward) following treatment for infantile esotropia, usually lead to good long-term alignment, and is only an apparent complication. Severe complications, such as globe perforation and retrobulbar hemorrhage are rare. [16] [1] No systemic side effects have been reported in patients treated for strabismus, nor has immunity to botulinum toxin developed, even after multiple injections.

Bupivacaine

Bupivacaine injection is currently the only pharmacologic treatment clinically shown to strengthen and shorten extraocular muscles. [21] [22] [9] [23] Myogenic growth factors (IGF and FGF) have only been tested in animals. [24] [25]

Long used as an anesthetic in cataract surgery, bupivacaine was found to sometimes cause strabismus, presumably because it had been inadvertently injected into a muscle. Initially attributed to simple myotoxic damage, [26] [ unreliable medical source ] careful observation of the clinical time course showed more complex sequelae, including increased contractility and elevated stiffness. [27] [ unreliable medical source ] It was later clarified that bupivacaine injection induces modest hypertrophy, which could be harnessed to produce muscle shortening and alignment corrections. [22] [ unreliable medical source ] Bupivacaine injection is currently an office procedure performed under topical anesthesia in cooperative adults, and has been used as an alternative to strabismus surgery to treat moderate-sized, non-paralytic, non-restrictive strabismus since 2006. Stability of alignment correction has been documented for up to 5 years. [22] [23] [ unreliable medical source ]

Adjuvants

The length at which the muscle treated with bupivacaine regenerates is determined by the length at which it is held during regeneration. Injection of small dose of botulinum toxin in the antagonist muscle weakens it for a few weeks, preventing stretching of the bupivacaine-injected muscle, allowing it to regenerate shorter than otherwise, thereby providing about twice the alignment correction of bupivacaine alone. The effectiveness of a bupivacaine injection may be increased by combining it with the vasoconstrictor epinephrine, which lengthens exposure time. [22]

Surgery

Treatment is usually surgical, performed at the insertional ends of extraocular muscles (where they attach to the globe). Resection surgery removes tissue in order to stretch a muscle, increasing its elastic force; recession moves an insertion so as to reduce stretch, and so reduce elastic force; transposition moves an insertion “sideways”, sacrificing one direction of muscle action for another; posteriorfixation relocates a muscle's effective insertion to a mechanically disadvantageous position. All are kinds of compensatory impairment. Pharmacologic injection treatments, in contrast, offer the possibility of directly increasing or decreasing contractile muscle strength and elastic stiffness, as well as changing muscle length, without removing tissue or otherwise compromising orbital mechanics. [28] [ unreliable medical source ] [21] [ unreliable medical source ] [22] The idea of treating strabismus by cutting some of the extraocular muscle fibers was published in American newspapers by New York oculist John Scudder in 1837 [29]

Spherical lenses and miotic eye drops can provide relief in some types of horizontal strabismus by biasing the neural link between convergence (orienting the lines of sight for near objects) and accommodation (focusing), and prism lenses can relieve diplopia (double vision) by refracting the visual axis, [30] [ unreliable medical source ] [31] [ unreliable medical source ] but these treatments don't address the underlying muscular imbalance, and are not further considered here.

Drug treatment vs surgery

With surgery, results are seen in a few days. After bupivacaine injection the muscle is inactivated by the drug's anesthetic effect for a day, and weakened by myofiber destruction for a week or so, after which regeneration and hypertrophy over 2–3 weeks gradually achieves the corrected alignment. If bupivacaine injection is combined with a small dose of botulinum toxin in the antagonist muscle, eye deviation during regeneration is minimized. Strabismus surgery generally sacrifices one mechanical effect to gain another, and always causes scarring, both of which may make any subsequent procedures more difficult. Bupivacaine injection treatment, in contrast, directly increases muscle strength and reduces length. Strabismus surgery requires an operating room, anesthetist, and other personnel, whereas bupivacaine injection in cooperative adults is an office procedure taking only a few minutes. Bupivacaine injection is not effective in paralyzed or atrophic muscles, or where there are restrictions to movement elsewhere in the orbit (e.g., fibrotic muscles). Very small misalignments might be better treated surgically because of the risk of “overcorrection”, which tends to cause diplopia (double vision). [21] [22] [9] [23]

Orthoptics

A complex approach to non-surgical management of strabismus (wandering eye), amblyopia (lazy eye) and eye movement disorders may include a variety of vision therapy methods, primarily directed at the abnormal retinal correspondence management such as eye occlusion with an eye patch, binocular vision training using a haploscope and many others. The orthoptic therapy can be used either before or after the surgical treatment, as it is prescribed by an eye care specialist.

Related Research Articles

<span class="mw-page-title-main">Botulinum toxin</span> Neurotoxic protein produced by Clostridium botulinum

Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction, thus causing flaccid paralysis. The toxin causes the disease botulism. The toxin is also used commercially for medical and cosmetic purposes.

<span class="mw-page-title-main">Esotropia</span> Form of strabismus

Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usually involves more severe axis deviation than esophoria. Esotropia is sometimes erroneously called "lazy eye", which describes the condition of amblyopia; a reduction in vision of one or both eyes that is not the result of any pathology of the eye and cannot be resolved by the use of corrective lenses. Amblyopia can, however, arise as a result of esotropia occurring in childhood: In order to relieve symptoms of diplopia or double vision, the child's brain will ignore or "suppress" the image from the esotropic eye, which when allowed to continue untreated will lead to the development of amblyopia. Treatment options for esotropia include glasses to correct refractive errors, the use of prisms, orthoptic exercises, or eye muscle surgery. The term is from Greek eso meaning "inward" and trope meaning "a turning".

<span class="mw-page-title-main">Strabismus</span> Eyes not aligning when looking at something

Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at an object can alternate. The condition may be present occasionally or constantly. If present during a large part of childhood, it may result in amblyopia, or lazy eyes, and loss of depth perception. If onset is during adulthood, it is more likely to result in double vision.

<span class="mw-page-title-main">Superior rectus muscle</span> Extraocular muscle that elevates the eye

The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve (III). In the primary position, its primary function is elevation, although it also contributes to intorsion and adduction. It is associated with a number of medical conditions, and may be weak, paralysed, overreactive, or even congenitally absent in some people.

<span class="mw-page-title-main">Inferior rectus muscle</span>

The inferior rectus muscle is a muscle in the orbit near the eye. It is one of the four recti muscles in the group of extraocular muscles. It originates from the common tendinous ring, and inserts into the anteroinferior surface of the eye. It depresses the eye (downwards).

<span class="mw-page-title-main">Medial rectus muscle</span> Extraocular muscle that rotates the eye medially

The medial rectus muscle is a muscle in the orbit near the eye. It is one of the extraocular muscles. It originates from the common tendinous ring, and inserts into the anteromedial surface of the eye. It is supplied by the inferior division of the oculomotor nerve (III). It rotates the eye medially (adduction).

<span class="mw-page-title-main">Inferior oblique muscle</span> Part of the eye

The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit. The inferior oblique is one of the extraocular muscles, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the eye (insertion). The inferior oblique is innervated by the inferior branch of the oculomotor nerve.

<span class="mw-page-title-main">Vergence</span> Simultaneous movement of eyes in binocular vision

A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision.

<span class="mw-page-title-main">Exotropia</span> Visual disorder where eyes work independently

Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence of poor vision in one eye. Infantile exotropia is seen during the first year of life, and is less common than "essential exotropia" which usually becomes apparent several years later.

<span class="mw-page-title-main">Sixth nerve palsy</span> Medical condition

Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI, which is responsible for causing contraction of the lateral rectus muscle to abduct the eye. The inability of an eye to turn outward, results in a convergent strabismus or esotropia of which the primary symptom is diplopia in which the two images appear side-by-side. Thus, the diplopia is horizontal and worse in the distance. Diplopia is also increased on looking to the affected side and is partly caused by overaction of the medial rectus on the unaffected side as it tries to provide the extra innervation to the affected lateral rectus. These two muscles are synergists or "yoke muscles" as both attempt to move the eye over to the left or right. The condition is commonly unilateral but can also occur bilaterally.

<span class="mw-page-title-main">Hypertropia</span> Condition of misalignment of the eyes

Hypertropia is a condition of misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye. Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye. Dissociated vertical deviation is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive.

<span class="mw-page-title-main">Strabismus surgery</span> Surgery to correct strabismus

Strabismus surgery is surgery on the extraocular muscles to correct strabismus, the misalignment of the eyes. Strabismus surgery is a one-day procedure that is usually performed under general anesthesia most commonly by either a neuro- or pediatric ophthalmologist. The patient spends only a few hours in the hospital with minimal preoperative preparation. After surgery, the patient should expect soreness and redness but is generally free to return home.

Chronic progressive external ophthalmoplegia (CPEO) is a type of eye disorder characterized by slowly progressive inability to move the eyes and eyebrows. It is often the only feature of mitochondrial disease, in which case the term CPEO may be given as the diagnosis. In other people suffering from mitochondrial disease, CPEO occurs as part of a syndrome involving more than one part of the body, such as Kearns–Sayre syndrome. Occasionally CPEO may be caused by conditions other than mitochondrial diseases.

Infantile esotropia is an ocular condition of early onset in which one or either eye turns inward. It is a specific sub-type of esotropia and has been a subject of much debate amongst ophthalmologists with regard to its naming, diagnostic features, and treatment.

Dissociated vertical deviation (DVD) is an eye condition which occurs in association with a squint, typically infantile esotropia. The exact cause is unknown, although it is logical to assume it is from faulty innervation of eye muscles.

Cyclotropia is a form of strabismus in which, compared to the correct positioning of the eyes, there is a torsion of one eye about the eye's visual axis. Consequently, the visual fields of the two eyes appear tilted relative to each other. The corresponding latent condition – a condition in which torsion occurs only in the absence of appropriate visual stimuli – is called cyclophoria.

<span class="mw-page-title-main">Stereopsis recovery</span>

Stereopsis recovery, also recovery from stereoblindness, is the phenomenon of a stereoblind person gaining partial or full ability of stereo vision (stereopsis).

Botulinum toxin therapy of strabismus is a medical technique used sometimes in the management of strabismus, in which botulinum toxin is injected into selected extraocular muscles in order to reduce the misalignment of the eyes. The injection of the toxin to treat strabismus, reported upon in 1981, is considered to be the first ever use of botulinum toxin for therapeutic purposes. Today, the injection of botulinum toxin into the muscles that surround the eyes is one of the available options in the management of strabismus. Other options for strabismus management are vision therapy and occlusion therapy, corrective glasses and prism glasses, and strabismus surgery.

Daniel Mojon is a Swiss ophthalmologist and ophthalmic surgeon who is considered to be the inventor of minimally invasive strabismus surgery (MISS), a method of surgically correcting squinting that uses only very small incisions of two to three millimeters and is supposed to lead to quicker rehabilitation and wound healing. Daniel Mojon is president of the program committee of the Swiss Academy of Ophthalmology (SAoO).

Alan Brown Scott was an American ophthalmologist specializing in eye muscles and their disorders, such as strabismus. He is best known for his work in developing and manufacturing the drug that became known as Botox, research described as "groundbreaking" by the ASCRS.

References

  1. 1 2 3 4 5 Rowe, Fiona J.; Noonan, Carmel P. (2 March 2017). "Botulinum toxin for the treatment of strabismus". The Cochrane Database of Systematic Reviews. 2017 (3): CD006499. doi:10.1002/14651858.CD006499.pub4. ISSN   1469-493X. PMC   6464099 . PMID   28253424.
  2. ↑ Chatzistefanou KI, Mills MD (2000). "The role of drug treatment in children with strabismus and amblyopia". Paediatric Drugs. 2 (2): 91–100. doi:10.2165/00148581-200002020-00002. PMID   10937461. S2CID   22861085.
  3. 1 2 Mcneer KW, Magoon EH, Scott AB (1999). "Chemodenervation therapy: Techniques and indications". In Santiago AP, Rosenbaum AL (eds.). Clinical strabismus management. Philadelphia: Saunders. ISBN   978-0-7216-7673-9.
  4. ↑ de Alba Campomanes AG, Binenbaum G, Campomanes Eguiarte G (Apr 2010). "Comparison of botulinum toxin with surgery as primary treatment for infantile esotropia". Journal of AAPOS. 14 (2): 111–6. doi:10.1016/j.jaapos.2009.12.162. PMID   20451851.
  5. ↑ Magoon E, Cruciger M, Scott AB, Jampolsky A (May 1982). "Diagnostic injection of Xylocaine into extraocular muscles". Ophthalmology. 89 (5): 489–91. doi:10.1016/s0161-6420(82)34764-8. PMID   7099568.
  6. ↑ Mendonça TF, Cronemberger MF, Lopes MC, Nakanami CR, Bicas HE (2005-04-01). "[Electromyograph assistance and Mendonça's forceps--a comparison between two methods of botulinum toxin A injection into the extraocular muscle]". Arquivos Brasileiros de Oftalmologia. 68 (2): 245–9. doi: 10.1590/S0004-27492005000200017 . PMID   15905949.
  7. ↑ Park CY, Park SE, Oh SY (2004). "Acute effect of bupivacaine and ricin mAb 35 on extraocular muscle in the rabbit". Current Eye Research. 29 (4–5): 293–301. doi:10.1080/02713680490516125. PMID   15590475. S2CID   2657530.
  8. ↑ Scott AB (1991). "When considering Oculinum (botulinum toxin type A) injection for the treatment of strabismus, can the surgeon anticipate different results in patients who have had previous strabismus surgery?". Arch. Ophthalmol. 109 (11): 1510. doi:10.1001/archopht.1991.01080110044031. PMID   1755729.
  9. 1 2 3 Scott AB, Alexander DE, Miller JM (2007). "Bupivacaine strengthens eye muscles". Proceedings of the 31st European Strabismological Association: 177–180.
  10. ↑ Scott AB, Rosenbaum A, Collins CC (Dec 1973). "Pharmacologic weakening of extraocular muscles". Investigative Ophthalmology. 12 (12): 924–7. PMID   4203467.
  11. ↑ Burgen AS, Dickens F, Zatman LJ (Aug 1949). "The action of botulinum toxin on the neuro-muscular junction". The Journal of Physiology. 109 (1–2): 10–24. doi:10.1113/jphysiol.1949.sp004364. PMC   1392572 . PMID   15394302.
  12. 1 2 Montecucco C, Schiavo G, Tugnoli V, de Grandis D (Oct 1996). "Botulinum neurotoxins: mechanism of action and therapeutic applications". Molecular Medicine Today. 2 (10): 418–24. doi:10.1016/1357-4310(96)84845-3. PMID   8897436.
  13. 1 2 Tighe AP, Schiavo G (Jun 2013). "Botulinum neurotoxins: mechanism of action". Toxicon. 67: 87–93. doi:10.1016/j.toxicon.2012.11.011. PMID   23201505.
  14. ↑ Scott AB (1994). "Change of eye muscle sarcomeres according to eye position". Journal of Pediatric Ophthalmology and Strabismus. 31 (2): 85–8. doi:10.3928/0191-3913-19940301-05. PMID   8014792.
  15. ↑ Elston JS, Lee JP, Powell CM, Hogg C, Clark P (Oct 1985). "Treatment of strabismus in adults with botulinum toxin A". The British Journal of Ophthalmology. 69 (10): 718–24. doi:10.1136/bjo.69.10.718. PMC   1040726 . PMID   4052354.
  16. 1 2 Crouch ER (Oct 2006). "Use of botulinum toxin in strabismus". Current Opinion in Ophthalmology. 17 (5): 435–40. doi:10.1097/01.icu.0000243018.97627.4c. PMID   16932060. S2CID   25420765.
  17. ↑ Ribeiro Gde B, Almeida HC, Velarde DT (2012-12-01). "Crotoxin in humans: analysis of the effects on extraocular and facial muscles". Arquivos Brasileiros de Oftalmologia. 75 (6): 385–9. doi: 10.1590/s0004-27492012000600002 . PMID   23715138.
  18. ↑ Kowal L, Wong E, Yahalom C (Dec 2007). "Botulinum toxin in the treatment of strabismus. A review of its use and effects". Disability and Rehabilitation. 29 (23): 1823–31. doi:10.1080/09638280701568189. PMID   18033607. S2CID   19053824.
  19. ↑ Miller JM, Demer JL (1992). "Biomechanical analysis of strabismus". Binocular Vision and Eye Muscle Surgery Quarterly. 7 (4): 233–248.
  20. ↑ Ribeiro Gde B, Almeida HC, Velarde DT, Sá ML (Oct 2012). "Study of crotoxin on the induction of paralysis in extraocular muscle in animal model". Arquivos Brasileiros de Oftalmologia. 75 (5): 307–12. doi: 10.1590/s0004-27492012000500002 . PMID   23471322.
  21. 1 2 3 Scott AB, Miller JM, Shieh KR (Dec 2009). "Treating strabismus by injecting the agonist muscle with bupivacaine and the antagonist with botulinum toxin". Transactions of the American Ophthalmological Society. 107: 104–9. PMC   2814569 . PMID   20126486.
  22. 1 2 3 4 5 6 Miller JM, Scott AB, Danh KK, Strasser D, Sane M (Dec 2013). "Bupivacaine injection remodels extraocular muscles and corrects comitant strabismus". Ophthalmology. 120 (12): 2733–40. doi:10.1016/j.ophtha.2013.06.003. PMID   23916485.
  23. 1 2 3 Scott AB, Alexander DE, Miller JM (Feb 2007). "Bupivacaine injection of eye muscles to treat strabismus". The British Journal of Ophthalmology. 91 (2): 146–8. doi:10.1136/bjo.2006.110619. PMC   1857611 . PMID   17135337.
  24. ↑ Anderson BC, Christiansen SP, Grandt S, Grange RW, McLoon LK (Jun 2006). "Increased extraocular muscle strength with direct injection of insulin-like growth factor-I". Investigative Ophthalmology & Visual Science. 47 (6): 2461–7. doi:10.1167/iovs.05-1416. PMC   3039316 . PMID   16723457.
  25. ↑ Mcloon LK, Anderson B, Christiansen SP (2006). "Effect of basic fibroblast growth factor (fgf2) on force generation in rabbit extraocular muscle". Investigative Ophthalmology & Visual Science. 47 (13): 2930.
  26. ↑ Rainin EA, Carlson BM (Sep 1985). "Postoperative diplopia and ptosis. A clinical hypothesis based on the myotoxicity of local anesthetics". Archives of Ophthalmology. 103 (9): 1337–9. doi:10.1001/archopht.1985.01050090089038. PMID   4038126.
  27. ↑ Goldchmit M, Scott AB (1994). "Avaliacao da motilidade extrinseca ocular de pacientes facectomizados sob anesthesia retrobulbar". Arq. Bras. Oftalmol. 57 (2): 114–116. doi: 10.5935/0004-2749.19940059 .
  28. ↑ Miller JM (1989). "Functional anatomy of normal human rectus muscles". Vision Research. 29 (2): 223–40. doi:10.1016/0042-6989(89)90126-0. PMID   2800349. S2CID   42189288.
  29. ↑ Leffler CT, Schwartz SG, Le JQ (2017). "American Insight into Strabismus Surgery before 1838". Ophthalmology and Eye Diseases. 9: 1179172117729367. doi:10.1177/1179172117729367. PMC   5598791 . PMID   28932129.
  30. ↑ Mulvihill A, MacCann A, Flitcroft I, O'Keefe M (Jul 2000). "Outcome in refractive accommodative esotropia". The British Journal of Ophthalmology. 84 (7): 746–9. doi:10.1136/bjo.84.7.746. PMC   1723536 . PMID   10873987.
  31. ↑ Hill K, Stromberg AE (Mar 1962). "Echothiophate iodide in the management of esotropia". American Journal of Ophthalmology. 53 (3): 488–94. doi:10.1016/0002-9394(62)94880-8. PMID   13907355.
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