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Principles of strabismus surgery
- 1. PG - PuneethIsloor Moderator – Dr. Shubhashree Karat
- 2. ANATOMY AND ACTIONS Easy mnemonics – SIN RAD and SLIM Muscle Primary action Secondary action Tertiary Action SR Elevation intorsion Adduction IR Depression extorsion Adduction SO Intorsion depression Abduction IO Extorsion elevation Abduction MR Adduction - - LR Abduction - -
- 3. Blood supply –Ophthalmic artery Muscular arteries (2) Medial .M.A Lateral .M.A Supplies MR,IR ,IO Supplies LR,SR,SO,LPS anterior ciliary arteries - emerge on orbital surface from these muscular arteries - 10 -12 mm from the insertions 2 anterior ciliary arteries from all muscles except LR The blood supply of IO muscle enters it just lateral to IR – this neurovascular bundle can get disinserted while recessing IO
- 4. CONCEPT OF ARCOF CONTACT The point at which the tendon first touches globe – Tangential point The arc of contact is distance between the tangential point and the centre of anatomic insertion of the muscle MR – 6 mm , LR – 15 mm , SR-8.4mm, IR-9mm Power of a muscle is proportionate to its arc of contact hence recession weakens muscle by reducing arc
- 5. When a musclecontracts , it produces a force that rotates the globe The rotational force α length of the moment arm (m) rotational force α force of muscle contraction (F) Rotational force = m × F
- 6. General goals ofstrabismus surgery To restore binocular vision To improve ocular alignment To enlarge the field of single binocular vision To alleviate an abnormal head posture To improve the aesthetic appearance of patient Goals should be prioritised based on the cause of strabismus.
- 7. PRE-OPERATIVE ASSESSMENT History– Rule out neurological diseases - Previous family photographs(FAT) - Document time of onset of strabismus - Past anesthestic complications and bleeding diatheses -Past history of trauma -Past history of strabismus surgery elsewhere
- 8. Pre opExamination – Look for nystagmus , anomalous head posture Lid abnormalities – epicanthus ,ptosis,telecanthus Visual acuity recording Cycloplegic refraction Anterior segment – Look for conjunctival scars,blebs - Scleral buckle, scleral ectasia Fundus – Macular pathology , Chorioretinal scarring
- 9. Identify ifeccentric fixation is present Test for ductions and versions and vergences FDT and FGT in adults pre-operatively Orbital imaging – only in case of thyroid myopathy and slipped or lost muscle .Not routinely done. Anesthesia – GA - LA in adults – Sub tenon’s is preferred.
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- 11. ANATOMICAL CONSIDERATIONS –GENERAL PRINCIPLES Distance of each rectus muscle from limbus must be taken into consideration. The muscle insertions at new locations must be splayed and not narrow – otherwise central sag occurs. While performing vertical transpositions of horizontal recti ,care should be taken to keep the muscle shift concentric to limbus. Never operate on 3 muscles at once – to reduce risk of anterior segment ischemia
- 12. Sclera isthinnest at insertion site of recti .Hence 0.5 mm stump of muscle should be left for resection re-suturing Avoid damage to vortex veins and tenons during supramaximal recessions involving posterior sclera Establish symmetry between two eyes if it doesn’t exist and maintain it when it exists. In patients with high grade stereopsis , caution while operating on SO – as it could induce vertical diplopia
- 13. INCISION TYPES Fornix incisionLimbal incision Fornix approach - Preferred for surgery of oblique muscles - Made at a point 8- 9 mm from the limbus Advantages - Access to more number of muscles at a time -More patient comfort -Less scarring -Ease of construction and closure Disadvantage – For large resections cannot resect conjunctiva - Cannot approach posterior orbit if needed - Increased risk of conjunctival tear
- 15. Limbal incision –Used for rectus muscle surgeries
- 16. Strabismus surgerycorrects ocular misalignment by at least 4 different mechanisms - Slackening a muscle - Recession -Tightening a muscle – Resection , plication -Reducing moment arm – Faden procedure -Changing vector force by transposition
- 17. STRABISMUS SURGERIES WEAKENINGPROCEDURES OF RECTI STRENGTHENING PROCEDURES OF RECTI WEAKENING PROCEDURES OF OBLIQUES STRENGTHENING OF SUPERIOR OBLIQUE
- 18. WEAKENING PROCEDURESOF RECTI MUSCLES 1)Conventional recession 2)Hang back recession 3)Adjustable suture technique 4)Retroequatorial myopexy (Faden) 5)Recession of vertical recti 6)Slanting recession 7)Marginal myotomy and myectomy
- 19. 1.CONVENTIONAL RECESSION Principle –Movesthe muscle insertion CLOSER to the ORIGIN creating a muscle slack The muscle slack reduces muscle strength as per starling ‘s length –tension curve It does not reduce the moment arm when eye is in primary position The muscle should be re-inserted within the length of its arc of contact Hence , there is maximum limit up to which a recession can be done for each muscle
- 20. A recessionhas its greatest effect in the field of action of the muscle. On rotation of eye away from recessed muscle , 2 things happen - Recessed muscle slack is reduced - The recessed muscle is inhibited by reciprocal inhibition(Sherrington s law)
- 21. Procedure Anesthesia Lidsretracted by self retaining speculum FDT done Limbal conjunctival incision is made and two radial incisions made at the ends of the limbal incision The intermuscular septum is button holed The jameson s hook and the green s hook are passed underneath the muscle
- 22. Check ligamentsand intermuscular septum are separated 2 interlocking loops of 6-o vicryl are passed at the two ends of muscle insertions Muscle is cut with tenotomy scissors leaving a stump of 0.5 mm Measurement of recession is made with callipers and the recessed muscle is sutured at the new site
- 25. 2 .HANG BACKRECESSION Principle -Suspends the muscle back, posterior to scleral insertion , with a suture to weaken the muscle. Small to medium sized recessions of 3- 6 mm can cause overcorrection because of central muscle sag
- 26. Indications - Asupramaximal recession is needed but unable to pass suture posteriorly due to risk of scleral perforation - Recession over a retinal buckle - Recession over an area of scleral ectasia as in high myopes - Large recession of a tightly contracted muscle Advantage – Needle passes through thick anterior sclera and excellent exposure Disadvantage – Narrowing of muscle insertion causing central muscle sag
- 28. 3. ADJUSTABLE SUTURETECHNIQUE Principle – Here recession allows fine –tuning of ocular movements in the immediate post-op period Procedure -Performed in 2 stages 1st stage – GA or LA .Recessed muscle is sutured such that the sutures can be made loose and muscle recession can be varied. 2nd stage – Readjustment is made within 24 hours of the first surgery under local anesthesia.
- 29. The adjustmentscan be made using a bow-tie knot or by a sliding noose Not recommended for children less than 15 years of age as it needs cooperation for adjustment stage.
- 30. Indications - Large anglestrabismus where results are inconsistent - Paralytic strabismus - Restrictive diseases – Thyroid myopathy - Previously injured extra-ocular muscles where muscle function assessment may be inaccurate
- 31. 4. RETROEQUATORIAL MYOPEXY(FADENS) -Principle -The muscle is sutured posterior to its insertion farther than the limit of its arc of contact - It shortens the lever arm - It reduces the moment arm only when the eye rotates towards the muscle sutured.
- 33. It isusually combined with a muscle recession as its weakening effect alone is not much Best suited for MR as it has the shortest arc of contact Works the least with LR as it has a long arc of contact Measurements for various muscles - MR – 12- 14 mm - LR - 16-20 mm - SR and IR – 14-16 mm
- 34. Indications fora Faden - Paralytic strabismus – In case of a LR palsy ,Faden of the contralateral MR is done . Used when patient is orthotropic in primary position but has diplopia on gaze towards paretic muscle. - Duane ‘s retraction - Contralateral MR - DVD – Superior recti - Nystagmus blockage syndrome – MR When combining with a recession , the muscle must be fixed at a distance obtained by subtracting the Amount of recession from the total faden.
- 35. 5. RECESSION OFVERTICAL RECTI Principle – The check ligaments for the vertical recti are linked to whitnall ‘s ligament for SR lockwood’s ligament for IR Hence ,While recessing IR ,care must be taken to separate it from lockwood s ligament and to prevent lower lid retraction Indications- - DVD - Thyroid myopathy -Congenital fibrosis Does not exceed 5mm in these 3 indications
- 36. 6. SLANTING RECESSIONS For esotropia, A- pattern : both MR recessed with Upper end> lower end V-Pattern : Both MR …..lower end > upper end Difference of 3-5 mm between the upper and lower ends For exotropia, A-Pattern : Both LR ……Lower end > upper end V –Pattern : Both LR …….Upper end > Lower end
- 37. 7.MARGINALMYOTOMY Principle -Several cutsare made alternatively at the two borders of the muscle. Indication – To weaken a muscle that has been maximally recessed They are transverse cuts in the muscle of atleast 2/3 width. MYECTOMY – used only for inferior oblique
- 38. WEAKENING PROCEDURESOF RECTI STRENGTHENING PROCEDURES OF RECTI WEAKENING PROCEDURES OF OBLIQUES STRENGTHENING OF SUPERIOR OBLIQUE
- 39. TIGHTENING PROCEDURES ONRECTI 1. Resection 2. Advancement 3. Double-breasting or tucking 4. Transposition of adjacent muscles
- 40. 1.RESECTION It isthe most common procedure for strengthening Involves excision of the tendinous part only If excess resection is done , it will weaken the muscle Hence For MR – maximum limit is 6 mm For LR - maximum limit is 8mm
- 41. Procedure Anesthesia Lidsretracted by self retaining speculum FDT done Limbal conjunctival incision is made and two radial incisions made at the ends of the limbal incision The intermuscular septum is button holed The jameson s hook and the green s hook are passed underneath the muscle Check ligaments and intermuscular septa are separated
- 42. Measurement ofthe resection is marked with calipers ensuring that the muscle is not stretched Two double armed vicryl 6-0 sutures are passed through muscle in an interlocking fashion A muscle clamp is applied 2 mm distal to sutures and the green’s hook removed and muscle is resected and cut leaving 0.5 mm stump Conjunctiva is re-apposed
- 46. 2. ADVANCEMENT Principle- Themuscle is re-inserted closer to limbus , thus making it more taut - increases arc of contact Indications - It is the ideal choice in a squint where recession has been done earlier - In paralytic squint , advancement may be combined with resection
- 47. 3. DOUBLE BREASTINGOR TUCKING Principle -It shortens the muscle by folding the muscle and suturing the folded muscle to muscle. Indications -Commonly used for plication of the superior oblique muscle in superior oblique palsy. The length of the tuck ranges from 6-12mm Advantages over resection Muscle is not disinserted and anterior ciliary vessels are not compromised It is reversible
- 48. 4.MUSCLE TRANSPOSITIONS Indications -Paralytic strabismus - Slipped or lost muscle Various procedures are – Knapp ‘s procedure - Jensen ‘s procedure -Hummelsheim procedure
- 49. KNAPP ‘S PROCEDURE Indications -Double elevator palsy -Lateral rectus palsy MR and LR muscles are transposed superiorly to the insertion of SR muscles A large posterior dissection is needed to separate it from the intermuscular septum and check ligaments
- 50. JENSEN ‘S PROCEDURE Indications – Lateral rectus palsy Here the adjacent muscles are tied together 12 mm posteriorly, but not disinserted Lateral halves of SR and IR are dissected Upper and lower halves of LR are dissected Lateral half of SR and upper half of LR are sutured Lateral half of IR and lower half of LR are sutured ADVANTAGE – Less chance of A/S ischemia
- 51. HUMMELSHEIM’S PROCEDURE It isa split tendon transfer technique to preserve anterior ciliary artery perfusion Indications – - Lateral rectus palsy - Lost medial rectus muscle Lateral halves of SR and IR are dissected upto 14 mm from their insertion They are reinserted adjacent to LR insertion and they should touch the LR insertion
- 52. Two modifications ofthe Hummelsheim are 1)Augmented Hummelsheim – Brooks Augmentation by resecting 4-6mm of transposed recti It tightens the transposition. Muscle union modification (Foster modification) Transposed and paretic muscles are sutured together and then to sclera , 4mm posterior to insertion.
- 53. Other transposition procedures 1)Callahan‘s procedure – Modification of jensen ‘s procedure used for elevator palsy. Upper half of MR ----sutured to ---medial half of SR Upper half of LR ----sutured to----lateral half of SR 2)O’Connor ‘s procedure – Here transposition of Vertical recti to LR is combined with LR tucking
- 54. 5. VERTICAL TRANSPOSITIONOF HORIZONTAL RECTI IN A-V PATTERNS WITHOUT OBLIQUE DYSFUCNTION For A Pattern For V Pattern MR shifted up(BE) MR shifted down(BE) LR shifted down(BE) LR Shifted up (BE) MR up ,LR down in MR down ,LR up monocular recession -resection
- 56. WEAKENING PROCEDURESOF RECTI STRENGTHENING PROCEDURES OF RECTI WEAKENING PROCEDURES OF OBLIQUES STRENGTHENING OF SUPERIOR OBLIQUE
- 57. WEAKENING PROCEDURESOF INFERIOR OBLIQUE Indications – 1)Superior oblique palsy (Ipsilateral IO) 2)V – pattern with IO overaction (Both eyes IO) 3) Double elevator palsy (Contralateral IO) 4)Dissociated Vertical deviation
- 58. Four Procedures 1)Inferior obliqueRecession 2)Anterior transposition with graded recession 3)Extirpation-denervation 4)Inferior oblique myectomy
- 59. 1)Inferior oblique recession- is of 2 types - Fink ‘s method - Produces only slackening - Park ‘s method – Produces slackening plus mild anterior transpositioning The IO is inserted at a point 2mm lateral and 3 mm posterior to lateral end of IR insertion
- 60. 2)Graded recession -Anterior transposition Recommended by Kenneth Wright for IO overaction The basis is that the more anterior the IO insertion , the greater the weakening effect The more anterior the placement of IO insertion , the more the muscle becomes a depressor Complication of this procedure is the postoperative limitation of elevation called “The anti elevation syndrome” Overaction I .O Placement +1 4mm posterior and 2 mm lateral to IR insertion +2 3mm posterior to IR insertion +3 1-2mm posterior to IR insertion +4 At IR insertion
- 61. 3)Denervation and extirpation– The nerve to IO is on posterior border of the muscle . It can be hooked and cauterised It results in laxity of muscle. Can be combined with myectomy
- 62. 4) Inferior obliquemyectomy It is faster to perform and does not need the muscle to be sutured to the sclera – less risk of perforation Muscle is allowed to retract into the tenon s capsule and the conjunctiva is closed
- 63. WEAKENING PROCEDURES OFSUPERIOR OBLIQUE They are two in number 1) Superior oblique tenotomy 2)Superior oblique tendon expander of Wright Indications for both – Brown’ syndrome
- 64. Approach toSO – Through fornix incision
- 65. 1.SUPERIOR OBLIQUE TENOTOMY Should be performed nasal to SR muscle A temporo-conjunctival incision is made and reflected nasally – This helps in many ways 1)To keep the nasal intermuscular septum intact and reduce tendon scarring down to sclera 2)To reduce the incidence of post operative SO palsy which occurs with temporal tenotomies (because they scar down to sclera)
- 66. 2)SUPERIOR OBLIQUE TENDON EXPANDEROF WRIGHT Principle : Controls the separation of the ends of tendon, allowing quantification of tendon separation A segment of silicone 240 retinal band is inserted between the cut ends of SO tendon . The first suture is placed 3 mm nasal to the superior rectus The maximum length of band is 7mm.Most can be managed with 5-6mm length of band.
- 68. WEAKENING PROCEDURESOF RECTI STRENGTHENING PROCEDURES OF RECTI WEAKENING PROCEDURES OF OBLIQUES STRENGTHENING OF SUPERIOR OBLIQUE
- 69. SUPERIOR OBLIQUE MUSCLESTRENGTHENING SO can be functionally divided into - Anterior 1/3 – Intorsion - Posterior 2/3 – Depression and abduction - Best accessed through fornix incision - Mainly two procedures 1)Harada-Ito –Procedure 2)Superior Oblique tendon tuck
- 70. 1.Harada – Itoprocedure Principle -Tightening the anterior fibres will induce intorsion without too much change in depression and abduction.
- 71. Indication -a partially recovered SO palsy where there is only large degree of extorsion It is of 2 types -1)Fell’s modificied Disinsertion technique – anterior fibres are disinserted and moved anteriorly and laterally then sutured at 8 mm posterior to superior border of LR insertion -2)Classic Harada –Ito – here the fibres are looped with a suture and displaced laterally
- 73. 2. Superior Obliquetendon tuck Indications –Usually done for congenital superior oblique palsy Also for traumatic superior oblique palsy If too tight a tuck , then iatrogenic browns syndome is seen Avoided by doing intraoperative FDT
- 74. COMPLICATIONS OF STRABISMUSSURGERY INTRAOPERATIVE POST-OPERATIVE Operation of wrong eye and wrong muscle Orbital cellulitis Hemorrhage Suture granulomas Scleral perforation Conjunctival cysts Central sag Dellen Muscle sheath ,tendon rupture and fat prolapse Over correction and undercorrection Loose sutures in the muscle Vomiting Slipped or lost muscle Anterior segment ischemia
- 75. LOST MUSCLE ORSLIPPED MUSCLE Most commonly affects MR and is difficult to retrieve MR has no fascial connections to obliques to prevent it from retracting posteriorly Can occur if the muscle slips during disinsertion and if the sutures have not been applied correctly A slipped muscle occurs when a muscle retracts posterior to the intended recession Lost muscle can also occur after orbital trauma or hemorrhage
- 76. Signs of lostmuscle -Limited ductions -Widening of lid fissure in the field of action of muscle Management - Find the muscle and surgically advance it to anterior sclera - If not retrieved , then a transposition procedure must be performed – Hummelsheims for MR.
- 77. ANTERIOR SEGMENT ISCHEMIA -Rare, but serious complication -Occurs if 3 or more recti surgery are done at a time especially in adults with atherosclerosis and hyperviscosity -Occurs in cases with previous radiotherapy and previous RD surgeries -Two vertical recti should not be operated with one horizontal rectus and especially the LR -The obliques do not contribute much to this
- 78. Signs - Corneal edema -Corneal thinning - Severe anterior uveitis - Iris atrophy - Distorted pupil - Cataract and phthisis in late stages Treatment – Steroids –local and systemic
Editor's Notes
- #14 Made at 8-9 mm to avoid extraconal pad of fat which begins at 10 mm from limbus
- #16 One must be careful not to include the plica seminularis at medial end and not to include the lateral canthus to prevent symblepharon Tenon ‘s capsule should not be sutured with the conjunctiva – can lead to unsightly hyperemia
- #19 6 mm for medial rectus and 8 mm for lateral rectus. 5mm and 10 mm as per dad(lol).A recession of less than 3 mm for MR and 4 mm for LR are ineffective.
- #20 6 mm for medial rectus and 8 mm for lateral rectus. 5mm and 10 mm as per dad(lol).A recession of less than 3 mm for MR and 4 mm for LR are ineffective
- #27 To reduce narrowing of muscle insertion and central muscle sag , there is hemi hang back recession in which the sutures are passed through scleral tunnel and then inserted.
- #35 In a right LR palsy , there is excessive impulse to Right LR and left MR by herring s law. So on right gaze, there is left eso. Hence we can do a faden of the left MR along with recession of right MR. Same holds good for duanes retraction.
- #41 The minimum limits for MR and LR is 3 and 4.5 mm respectively for it to be effective.
- #59 In Fink ‘s method - For a 8 mm recession of IO , a point 6 mm inferior and 6 mm posterior from the inferior end of LR insertion is chosen as the anterior point and another point 5-6 mm posterior to it in the same meridian For a 10 mm recession , the anterior point is 2 mm below the 8 mm point along the course of muscle For a 6 mm recession , the anterior point is 2 mm above the 8 mm point along the course of muscle
- #62 Strengthening procedure for IO are limited as it lacks a tendinous portion and hence resection cannotg be done. Double breasting can be tried.
- #63 IO strengthening procedures are rare . Used in treatment of incyclotorsion occuring after macular translocation surgery. Tucking of the inferior oblique can be done here.
- #76 It occurs if the sutures have been applied to anterior tenons instead of muscle tendon,so the muscle slips posteriorly while a pseudotendon of Connective tissue remains attached to sclera