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Ophthalmology
Surgical Management
Built from Strabismus Simplified, Second Edition
What’s inside
8 sections · 160 slides
Principles and preoperative assessment
- Goals of strabismus surgery
- Results depend on preoperative evaluation as much as on intraoperative dexterity A missed or unattended muscle can worsen the existing pattern Operating the opposite pair of muscles leaves the pattern worse despite a straight primary position Excessive monocular recession-resection buys alignment at the cost of a narrow palpebral aperture Globe retraction is the other price of over-large surgery on one eye Failure is minimised by understanding the principles, not by speed
- The final result depends on free movement of the tissues after surgery Handle tissue so as to avoid excessive restriction of the eye Minimally disturb the strength and leverage of the muscles Maintain the tissue planes so a revision is not made difficult Assume resurgery is always possible: about 10% need it
- Age-appropriate vision testing to recognise amblyopia, plus binocular status Full cycloplegic refraction and proper correction are mandatory Surgery done for the accommodative part of a deviation cannot be condoned Correct existing amblyopia, or confirm failure of amblyopia therapy, before deciding surgery In monocular squint with poor vision, refract the normal eye as well Accommodative innervation is driven by that normal eye and alters the deviation
- Prism bar cover test for near and distance fixation Measure in up- and downgaze to detect A and V phenomena Note any horizontal or vertical incomitance Record associated inferior or superior oblique overaction or underaction Control accommodation with correction and a 6/9 target for near and distance Operate for the static angle, never the dynamic angle
- Clinical test done preoperatively to reveal restrictive pathology Repeated at several points during surgery, not once Before starting, and after the conjunctival incision After dissecting check ligaments and intermuscular septum After hooking the muscle, to judge tension by the hook itself After disinsertion, after reinsertion, and after conjunctival closure
- Suxamethonium contracts muscle for the first 15-20 minutes and makes the test unreliable A non-depolarising relaxant such as pancuronium bromide avoids this Hold conjunctiva at the limbus with fixation or, preferably, Pierce-Hoskins forceps Do not retract the globe by pressure while testing the recti A conscious patient looks away from the direction tested, to relax that muscle Both direct and reverse leash restriction may coexist
- Described by Guyton to test tightness of the oblique muscles Unlike the rectus test, the globe is retracted to exaggerate oblique restriction Hold the limbus at the inferotemporal and superonasal quadrants Push the globe back into the orbit in full adduction, maintaining intorsion Bring it temporally while continuing to push backwards A normal or taut inferior oblique makes the globe pop up; a lax muscle does not
- Hold the limbus at the superotemporal and inferonasal quadrant positions Push the eye back into the orbit in full adduction, maintaining extorsion Bring it temporally while continuing to push back into the orbit A normal or taut superior oblique makes the globe pop up A click is felt by the examiner as the tendon passes A positive test after weakening indicates insufficient weakening
- Exaggerated forced duction testing for the superior oblique
- Introduced by Jampolsky to assess passive muscle force balance Asks whether surgical adjustment has disturbed the balance of passive forces Under general anaesthesia the globe is held at the limbus with two forceps The eye is passively rotated in the chosen direction, then the forceps released Note whether the globe springs back to primary position or stays deviated Repeat in the opposite direction: it should spring back with equal force
- Simple intraoperative test of the elasticity of a rectus muscle Done after disinsertion and after the sutures have been passed The muscle is pulled towards the opposite side A normal muscle can be advanced up to the centre of the cornea, eye straight ahead Failure to reach the corneal centre indicates contracture or fibrosis
- General anaesthesia relaxes convergence tone and alters the deviation The deviation at the end of surgery may not reflect the postoperative outcome Note the deviation once a surgical plane of anaesthesia is reached, before starting Record the difference between the pre-anaesthesia and post-anaesthesia deviation Add that difference to the on-table post-surgical deviation to estimate the final result Relevant only to general anaesthesia, not to retrobulbar or peribulbar blocks
- Communication must be unhindered, answering queries and fears It should prevent unnecessary or impossible expectations Some believe the globe is taken out, the muscles operated, and the eye replaced Squint surgery is a major procedure, as much as cataract, retina or keratoplasty surgery Explain the cosmetic limits: adnexal asymmetry, corneal opacity, cataract, coloboma True ptosis is a separate operation and is not corrected by squint surgery
- Inpatient admission is not essential but helps when general anaesthesia is planned Children with squint may have associated cardiac, nervous or dental problems The anaesthetist should be conversant with squint surgery Oculocardiac and oculorespiratory reflexes are commoner in strabismus surgery Malignant hyperthermia is also commoner in this population Patch the operated eye overnight; an apprehensive child may be opened after six hours
- Discuss the eye to be operated before surgery: patients may fear the wrong eye was done Usually the deviating eye is operated, keeping the other in reserve for a second surgery Both eyes may be operated at one sitting if the patient is taken into confidence In constant unilateral squint, explain the rationale before operating the fellow eye Dominant eye surgery gives no significantly better result and is usually avoided Fellow-eye surgery is needed in double elevator palsy and Duane's retraction syndrome
- The possibility and need for resurgery must be conveyed before operating About 10% of cases end up under- or overcorrected Some residual angles lie within fusional limits or are cosmetically acceptable The remainder require resurgery No strabismus surgery is 100% predictable and precise Expectations must be modest in paralytic cases
Anatomical and developmental considerations
- The limbus-to-insertion distance differs for each rectus and differs in infants Measure this distance at surgery and take it into account while recessing The two ends of a rectus differ from its midpoint in muscle-limbal distance Muscle width is about 10 mm, slightly less than the corneal diameter Restore that width at reattachment to preserve normal physiological action In vertical transposition, keep the shift concentric with the limbus
- A torsion induced under anaesthesia can make a surgeon operate a vertical rectus for a horizontal one Vertical recti insert obliquely, with about 23 degrees of obliquity Their temporal ends are further receded than their nasal ends Horizontal recti have upper and lower ends almost equidistant from the limbus Except the medial rectus, each rectus has an oblique muscle associated with it The lateral triangle of the limbus merges more indistinctly with sclera
- Anterior segment blood supply in strabismus surgery
- Surgery on both vertical recti combined with the lateral rectus can precipitate ischaemia Particular risk in older patients with arteriosclerosis syndromes If three adjacent recti must be operated, space the stages at least six weeks apart Obliques carry no anterior ciliary supply and add no ischaemic risk Cinching and double breasting spare the vessels because the muscle is not disinserted
- The sclera is thinnest at the rectus insertion, about 0.3 mm Leave at least a 0.5 mm muscle stump for resuturing after resection Take special care against globe penetration during supramaximal recession The same caution applies to faden surgery, where sutures are placed far posteriorly Hang-back recession exists partly to avoid posterior scleral passes in high myopes
- The muscle sheath should always be preserved Do not violate Tenon's capsule 8 mm posterior to the muscle insertion Breaching it lets orbital fat prolapse forward Prolapsed fat produces fibrofatty adhesions that restrict the eye Protect the vortex veins while working posteriorly
- The nerves to the recti are usually safe, entering about 26 mm from the insertion The nerve to the inferior oblique is the exception It lies at the crossing of the nasal border of the inferior rectus and the oblique That crossing point is within reach of inferior oblique and inferior rectus surgery The nerve is a fusiform structure on the posterior border of the inferior oblique
- The neonatal eye is still growing Axial length is 70% of the adult eye Volume is only half and surface area about one-third of the adult eye The anterior segment is 80% of adult size at birth The posterior segment develops over the next six months Recession or retroequatorial surgery before six months can be unpredictable
Choice of surgery: general principles
- Two broad categories of strabismus procedure
- Weakening and strengthening may be combined in one eye, or one procedure done on both eyes Symmetric procedures on the two eyes are not obligatory Try to establish symmetry where none exists, and maintain it where it exists The aim is symmetrising surgery Be guided by the excursion of the muscles, the versions and the ductions
- Convergence excess esotropia: bimedial recessions Divergence insufficiency esotropia: resection of both lateral recti Basic esotropia: monocular recession-resection, or bimedial recession by preference The difference between near and distance deviation drives the choice Nonaccommodative convergence excess is also an indication for faden on the medial recti
- Convergence insufficiency exotropia: medial rectus resection in both eyes Divergence excess exotropia: recession of both lateral recti Basic exotropia: a recession-resection procedure in one eye The pattern mirrors the logic used in esotropia
- Split the amount preferably between the two recti operated Avoid accomplishing a large correction on one muscle alone A single large muscle surgery corrects the primary position but induces incomitance Incomitance appears on extreme lateral gaze It can also alter lid position, causing ptosis from globe retraction Large deviations need three-muscle surgery; rarely all four recti are operated
- Associated oblique overactions must be tackled whenever present Leaving them untreated leaves the pattern uncorrected Where there is an A or V pattern without oblique overaction, operate the horizontal recti differently Vertical shifting of the horizontal recti is one option Slanting recession and resection is the alternative
Weakening procedures on the recti
- Recession: conventional, hang-back or hemi hang-back, adjustable Recession variants also include vertical transposition of horizontal recti and slanting recession Retroequatorial myopexy, the faden operation Marginal myotomy Myectomy Free tenotomy or disinsertion
- Weakening procedures on the rectus muscles
- A rectus or oblique is disinserted and reinserted closer to its origin This induces a slack or laxity in the muscle A lax muscle is less effective as its length-tension relationship changes The change follows Beisner's family of curves Within the arc of contact, torque is not unduly affected Recessed beyond the arc of contact, the muscle ceases to perform its action
- Recession of the medial rectus
- The maximum recession is limited by the functional equator, which depends on the arc of contact The functional equator is not the same as the anatomic equator For the lateral rectus it lies 2 mm posterior to the anatomic equator For the medial rectus it lies 2 mm anterior to the anatomic equator Beyond this point the muscle ceases to act on the globe
- Maximal recession in adults: 6 mm for medial rectus, 8 mm for lateral rectus In small children: 5.5 mm for medial rectus and 7 mm for lateral rectus Minimal effective recession: 3 mm for medial rectus, 4 mm for lateral rectus Below the minimum the procedure may simply be ineffective The minimal limits depend on the dynamics of ocular motility
- Safe limits of recession
- Suggested amount of surgical correction
- Recessions are graded weakening procedures and more predictable than any other They can be undone if necessary, or revisited to augment the effect Their effectiveness has made disinsertion and free tenotomy obsolete In free tenotomy there is no control over where the muscle reattaches Such procedures were difficult to undo or redo They survive only for a tight fibrotic rectus where recession is impossible
- Surgeon and assistant positions for each muscle
- Instruments used in strabismus surgery
- Age-appropriate anaesthesia, then clean the eye and adnexa with spirit and betadine and drape Apply an adhesive steridrape; keep both eyes clean and visible Under general anaesthesia keep the fellow eye hydrated with a wet cotton swab Retract the lids with a self-retaining speculum with blades to exclude lashes Perform forced duction testing, to be repeated at several later steps Make a limbal conjunctival incision after passing two limbal 6-0 silk or cotton sutures
- Two radial conjunctival incisions are made with blunt-ended spring scissors, at 90 degrees to each other Button-hole the intermuscular septum in the superonasal and inferonasal quadrants Hook the muscle with Jameson's hook, passed hugging the sclera to take the entire muscle Pass Green's hook from the other end to confirm the whole muscle is hooked Separate check ligaments and intermuscular septum under direct vision Excise excess Tenon's capsule around the insertion, sparing vessels, fascia and muscle sheath
- Pass two interlocking loops of 6-0 vicryl on 5-29 needles and secure a knot at each end of the insertion Each bite involves 3-4 mm at either end of the insertion Cut the muscle with tenotomy scissors, leaving a 0.5 mm stump Light cautery may be needed at the cut edge Measure the recession with calipers from the upper and lower ends Never grasp those ends with fixation forceps; hold the insertion at its middle
- Pass the two spatulated needles paralimbally, away from each other, at the marked points Ensure an insertion width of at least 8-10 mm Tie surgical knots while the assistant holds the knot against slippage and loosening Visualise the muscle and its attachments to exclude entrapment Reappose conjunctiva with four or more interrupted sutures Ensure no prolapse of Tenon's tissue at closure
- Surgical steps in recession of a rectus muscle
- The conjunctival incision is made 7-8 mm from the limbus in the lower or upper fornix A second small incision is made in Tenon's capsule at 90 degrees to the first The rectus is hooked with Jameson's hook followed by Green's hook The muscle is brought into the exposed site by a manoeuvre using a lens hook Examine the upper pole of the insertion to confirm the whole muscle is on the hook If it is not, hook the muscle again
- Conventional recession reinserts the muscle directly at the intended scleral point In hang-back recession, long suture ends span between the original insertion and the muscle The sutures themselves are placed at the site of the original insertion Indicated when a supramaximal recession is intended and posterior suture passes are difficult Particularly useful in high myopes, where posterior passes risk scleral perforation Also used where disinsertion or free tenotomy would otherwise be considered
- The weakening effect exceeds a conventional recession because of a central mid-width sag It leaves a narrower effective width of muscle A pseudotendon may form in the intervening space around the sutures That pseudotendon may shorten and produce a late undercorrection If the sutures give way or are absorbed, the result may be as bad as a disinsertion
- A modification in which the sutures pass through a scleral tunnel before reaching the original insertion The tunnel keeps the muscle width broader than in a full hang-back It reduces the chance of postoperative creeping forward from a long hang-back It retains the advantage of avoiding a far posterior scleral pass
- The position of a newly operated muscle can be modified using adjustable sutures Adjustment is allowed after the anaesthetic has worn off but before healing has begun The classical method is attributed to Jampolsky The recessed muscle is sutured so the tendon can be drawn forward for less recession Or allowed to retract posteriorly for more recession Requires a cooperative patient: surgery and adjustment under local or topical anaesthesia
- Indications for adjustable suture surgery
- Technique varies between surgeons; a limbal incision is preferred Hook the muscle and dissect intermuscular septum and check ligaments as usual Pass two separate sutures at the two ends of the muscle insertion Bring them straight, or through a scleral tunnel starting mid-distance to allow forward pull Tie the two ends together in a one-and-a-half knot; the half knot is opened at adjustment Resuture limbal conjunctiva with 5 mm of bare sclera; some surgeons use a sliding noose
- Three techniques of adjustable recession
- Readjustment is made within 24 hours: the evening after 5-6 hours, or the next morning Anaesthetise topically and insert a lid speculum Untie the temporary knot and make the adjustment The patient fixates a distant target and confirms alignment subjectively; a cover test is done Secure the knot finally to lock the suture and trim the excess It is easier to move an over-recessed muscle forward than to augment an under-recession
- Appearance before and after readjustment
- Adjustment endpoints by diagnosis and procedure
- Some surgeons delay adjustment to about a week for a more predictable outcome Delayed adjustment is not easy, because healing has begun It requires viscoelastic substances such as sodium hyaluronate Silicon sleeves may also be used to allow delayed adjustment
- Also called posterior fixation suture or faden, the German word for suture Devised by Cuppers The muscle is sutured to sclera posterior to its insertion, beyond the arc of contact This drastically shortens the lever arm It severely reduces the action of the muscle in its field of action Without a recession it does not alter length-tension relationship or primary position deviation
- Retroequatorial myopexy of the medial rectus
- Distance of the posterior fixation suture from the insertion
- Nonaccommodative convergence excess esotropia: medial recti Nystagmus blockage syndrome: medial recti Dissociated vertical deviation: superior recti Paralytic strabismus: the contralateral synergist Duane's retraction syndrome: the contralateral medial rectus As additional weakening over an already recessed muscle
- Without recession, pass 5-0 mersilene on small half-circle needles at the two ends The bites take the marked point on the muscle and the underlying sclera together Apply the knots carefully to prevent any loosening Bites in the muscle should be 3-4 mm on either side This includes at least 80% of the fibres in the fixation Pass a hook afterwards to confirm the posterior fixation
- When recession is combined, the muscle is fixed at the faden distance minus the recession For a 14 mm faden with a 4 mm recession, the muscle is fixed at 10 mm The scleral sutures are still passed at the full faden distance, 14 mm The recession of the required amount, 4 mm here, is then executed This gives weakening in primary position plus loss of lever arm in the field of action
- Myotomy may be marginal or central; central myotomy is not as effective Transverse cuts are made in the muscle, each at least two-thirds of the width Several cuts are made alternately at the two borders of the muscle This effectively lengthens the muscle, like straightening a Z Artery clamps crush the muscle before incision to prevent bleeding; cautery may also be used A traumatising procedure: a last resort in a maximally recessed muscle still needing weakening
- The correct term is myectomy, not myomectomy, which would mean excising a myoma Myectomy is another weakening procedure It is still performed on the inferior oblique by some surgeons Otherwise the procedure has become obsolete
Strengthening procedures on the recti
- Resection Advancement Double breasting or tucking Cinching Transpositioning of adjacent muscles
- Strengthening procedures on the rectus muscles
- The commonest strengthening procedure; it shortens the muscle and makes it more taut Efficiency improves by raising the muscle to a higher length-tension curve Resection implies excision of the tendinous part only If muscle mass is excised the muscle is weakened instead, which is a myectomy Maximum limits: 6 mm for medial rectus and 9 mm for lateral rectus Minimum limits: 3 mm for medial rectus and 4.5 mm for lateral rectus
- Steps one to nine are identical to a recession Mark the resection with calipers, ensuring the muscle is not stretched during marking Pass two double-armed 6-0 vicryl sutures, four needles in all, in an interlocking fashion Hold the loose ends with serrefines or bulldog clamps Apply a muscle clamp 2 mm distal to the sutures and remove Green's hook Cut the muscle carefully, leaving a 0.5 mm stump
- Pass the four needles through the stump with at least 5 mm separation between the upper and lower pairs This ensures at least 8 mm of muscle insertion width once knots are tied Adequate width prevents loosening of the knots Visualise the muscle to exclude entrapment Reappose the conjunctiva as for a recession Alternatively clamp and cauterise just in front of the bites, then cut and excise the segment
- Surgical steps in resection of a rectus muscle
- Alternative sequence for resection
- Fornix incision steps
- The muscle is reinserted closer to the limbus, stretching it and making it more taut It is the reverse of a recession Limited by the short limbus-to-muscle distance available Also limited by the risk of unsightly congestion in the paralimbal area It is the ideal choice in consecutive squint where a recession was previously done In some paralytic squint, advancement may be added to a resection
- Double breasting, or tenoplication, shortens the muscle without excising muscle mass The tendinous or muscular part is folded on itself Indicated in paralytic squint where a thin fragile muscle is present Tenoplication of the superior oblique is a common strengthening procedure for that muscle Cinching is a modified double breasting achieved by the path of the sutures In both, the muscle is not disinserted, so anterior ciliary vessels are spared
Anaesthesia, conjunctival incisions and sutures
- Given as 1% proparacaine or 4% lignocaine drops Effective in some highly cooperative patients Suited to short procedures without posterior manipulation Very useful on the adjustment day of adjustable suture surgery Also used for removing conjunctival silk sutures
- Continuous subconjunctival irrigation in the sub-Tenon's space, evaluated by Fujishima and colleagues 2 ml of 2% lignocaine is injected 15 mm from the limbus in the inferotemporal quadrant Delivered through a blunt cannula Reported good patient cooperation without much chemosis Retains motility of the eyeball, so correction can be evaluated on the table The author has no personal experience and does not recommend it
- Retrobulbar block is the commonest anaesthetic in adults and cooperative adolescents 3-4 ml of 2% lignocaine into the retrobulbar, intraconal space For prolonged procedures, mixed 1:1 with 0.5% bupivacaine Facial akinesia is usually not required Peribulbar block reduces the risk of retrobulbar haemorrhage and scleral perforation But it needs 8-10 ml and the resulting chemosis can be very difficult to work through
- Intratracheal intubation or a laryngeal mask, with halothane or nitrous oxide Used for most strabismus surgery in children and for uncooperative adults Preferred where complications or extensive surgery are expected Examples include slipped muscle and post-traumatic restrictive squint Also for squint following retinal detachment surgery Stop miotics, that is cholinesterase inhibitors, six weeks before surgery
- Ketamine can be used for smaller procedures Examples include adjustment in children and botulinum toxin injection in children It causes undesirable visual hallucinations Muscle tone is increased by ketamine, so the forced duction test becomes unreliable Intraocular pressure is also increased
- Limbal incision of von Noorden Over-the-muscle incision of Swan Paralimbal incision of Prem Prakash Fornix incision of Parks Minimal incision strabismus surgery, MISS
- Types of conjunctival incision
- A segmental peritomy with two radial incisions parallel to the palpebral aperture Results in an unrecognisable scar Gives good exposure of the recti and makes work in the correct tissue plane easy At the limbus conjunctiva and Tenon's are fused and can be lifted together Advantageous for conjunctival recession and for adjustable squint surgery Gives good undistorted exposure of the vertical recti and inferior obliques too
- Pass two 6-0 silk or cotton sutures at the ends of the proposed peritomy Make the limbal incision with a blade Take care not to go too deep and cut the sclera tangentially Make the radial incisions with blunt spring scissors
- Limbal approach to the medial rectus
- The incision is concentric with the limbus For the medial rectus it lies 1-2 mm anterior to the plica semilunaris For the lateral rectus it lies midway between the limbus and the lateral fornix Sclera is then exposed above and below the muscle by cutting Tenon's and the intermuscular membranes It leaves a bad scar Adhesions can form between conjunctiva and muscle if the muscle sheath is ruptured
- A compromise between the limbal and over-the-muscle incisions Less risk of direct injury to the rectus muscles, with good exposure Allows two paralimbal sutures at 2 mm and 4 mm from the limbus One suture retracts the globe, the other retracts the conjunctiva The incision is made between the two sutures with spring scissors Tenon's must be dissected before the muscle is exposed; it leaves a visible scar
- Made in the superior or inferior fornix, usually on bulbar conjunctiva Placed 8 mm from the limbus, just adjacent to the vertical recti Bare sclera is exposed by incising Tenon's capsule perpendicular to the conjunctival incision Leaves a hidden scar but yields poor exposure, difficult for beginners Once learnt it is preferred: better accepted, less irritative in the early postoperative phase Gives less visible hyperaemia and no visible scarring
- Recently described by Mojon Uses two small incisions at the upper and lower poles of the horizontal rectus insertions The muscle is sutured under the conjunctiva It does not lead to much advantage Only possible for small recessions And for plications in place of resections
- Indicated in long-standing deviations, or where scarring has made the conjunctiva tight A forced duction test positive before the conjunctival incision is relieved after it That relief identifies conjunctiva as the restricting tissue A 5 mm conjunctival recession is usually done It is easily incorporated with the limbal incision approach Redundant excess conjunctiva can instead be resected
- Conjunctival closure after recession and resection
- Recession and resection: 6-0 vicryl polyglactin on 5-29 double-armed spatulated needles Inferior oblique: the same, or 6-0 polyglactin on 5-28 double-armed half-circle needles Half-circle needles are better for the inferior oblique Posterior fixation and superior oblique expander: non-absorbable 5-0 mersilene Conjunctival closure: 8-0 vicryl, or 7-0 collagen Collagen dissolves earlier and causes less congestion
Pattern surgery and muscle transposition
- Horizontal recti can be recessed or resected with vertical transposition, that is shifting Done to correct associated A and V patterns Also done to correct associated vertical deviations along with the horizontal deviation The shift is made so the muscle insertion remains concentric to the limbus Both ends of the muscle must stay equidistant from the limbus
- A pattern: medial recti shifted up in both eyes A pattern alternative: lateral recti shifted down in both eyes A pattern, monocular recession-resection: medial rectus up and lateral rectus down V pattern: medial recti shifted down in both eyes V pattern alternative: lateral recti shifted up in both eyes V pattern, monocular recession-resection: medial rectus down and lateral rectus up
- Associated hypertropia: both the medial and lateral rectus are shifted down in the hypertropic eye Associated hypotropia: both the medial and lateral rectus are shifted up in the hypotropic eye Here both horizontal recti of the same eye move in the same direction This differs from pattern surgery, where the two muscles move oppositely
- Vertical transposition of the horizontal recti
- A and V patterns can also be treated by differential recession of the upper and lower ends A esotropia: both medial recti recessed, upper ends recessed more, by a 3-5 mm difference A exotropia: both lateral recti recessed, lower ends recessed more than the upper ends V esotropia: both medial recti recessed, lower ends recessed more V exotropia: both lateral recti recessed, upper ends recessed more
- A similar slanting resection places the sutures in the muscle in an oblique fashion For a V exotropia the medial rectus is resected more at the upper end In the same V exotropia the lateral rectus is recessed more at the upper end The principle mirrors slanting recession: differential effect at the two poles
- Slanting recession and resection of the horizontal recti
- Used where the function of a muscle cannot be improved by any strengthening procedure Adjacent muscles are transpositioned to aid or improve the action of the paralytic muscle In elevator underaction, medial and lateral recti are reinserted close to the superior rectus That procedure is Knapp's Indications: paralytic strabismus, and slipped or lost muscle Duane's retraction syndrome, rarely
- The essential prerequisite is absence of restriction of the antagonist, confirmed by forced duction test If the antagonist is tight, recess it first and free the adhesions around it Do not risk anterior segment ischaemia by operating two vertical recti and the lateral rectus together Knapp's on both horizontal recti with inferior rectus recession is safe in children and young adults Avoid it in older people with compromised circulation
- Performed for lateral rectus palsy The lateral halves of the superior and inferior recti are dissected up to 14 mm from their insertion They are reinserted adjacent to the lateral rectus insertion Only half of each vertical rectus is moved, so some anterior ciliary supply is preserved The same procedure can be used for a lost medial rectus
- Also for lateral rectus palsy The lateral halves of both vertical recti and the upper and lower halves of the lateral rectus are split free Each is dissected for about 14 mm from its insertion The lateral half of superior rectus and upper half of lateral rectus are tied with 5-0 mersilene near the equator The lateral half of inferior rectus and lower half of lateral rectus are tied similarly Supposed to carry less ischaemic risk, but ischaemia is still reported, probably from strangulation by the sutures
- Callahan's is a modification used for elevator palsy The upper halves of the medial and lateral recti are tied with the two halves of the superior rectus Peter's procedure is for the medial rectus in third cranial nerve palsy It uses the superior oblique, without removing it from the trochlea The tendon is shortened by 16-20 mm
- Knapp's for elevator palsy: transpositioning the horizontal recti to the superior rectus O'Connor's: lateral rectus cinch with transposition of the vertical recti to the lateral rectus Helveston's: preserved sclera used to transpose half of the vertical recti to the medial rectus Scott and Foster augmented the transposed muscle with posterior fixation sutures Those sutures are placed 8 mm posterior on the transposed half This vectorises the forces in line with the paralytic muscle
- Transposition procedures for paralytic strabismus
Vertical recti and the oblique muscles
- The vertical recti are intricately connected to the upper and lower lids Surgery of more than 5-6 mm without dissecting these attachments alters the palpebral aperture Inferior rectus recession: lower lid retraction, or ptosis of the lower lid Inferior rectus resection: elevation of the lower lid Superior rectus recession: upper lid retraction Superior rectus resection: ptosis of the upper lid
- The lid changes occur because the check ligaments of the vertical recti are linked to lid structures The superior rectus is linked to Whitnall's ligament The inferior rectus is linked to Lockwood's ligament Lockwood's ligament is a fibrous condensation with the fascia of inferior rectus and inferior oblique Dissecting these attachments prevents lid change during large recessions
- Recession and resection on the vertical recti are very effective More than 5 mm is usually not required; the minimum required amount is 2 mm Congenital muscle fibrosis may need 8-9 mm of inferior rectus recession With proper dissection of the attaching fibres, no significant lid changes are seen Slight lower lid depression is tolerated because surgery is bilateral Dysthyroid orbitomyopathy is the other condition needing large recessions
- Commonly combined with horizontal muscle surgery, as in A and V patterns Also done for cyclovertical problems such as superior oblique palsy In double elevator palsy the contralateral inferior oblique is addressed Obliques do not contribute to the anterior segment circulation So they can be combined with horizontal or vertical recti surgery with no added ischaemic risk A torsional Kestenbaum on all four obliques is safer than four vertical recti with horizontal shifting
- Generalised weakening: recession, myectomy, disinsertion Generalised weakening also includes denervation and extirpation Selective weakening: anteropositioning with recession Pure anteropositioning, without recession Total anteropositioning Recession of anterior fibres
- Generalised weakening: tenotomy by the temporal or nasal approach, and tenectomy Recession and translational recession L-lengthening, and silicon expander lengthening with a loop tenotomy at the insertion Selective weakening: posterior tenotomy and posterior tenectomy Recession of the anterior fibres Anteropositioning
- Inferior oblique generalised strengthening: advancement, resection or double breasting Inferior oblique selective strengthening: advancement of the anterior fibres Superior oblique generalised strengthening: tucking, that is tenoplication Superior oblique selective strengthening: tenting of the nasal fibres That is the Harada-Ito procedure or its modifications
- Anterior and posterior fibres of the oblique muscles
- Superior oblique palsy: the ipsilateral inferior oblique V-pattern deviations with overacting inferior obliques: both eyes Double elevator palsy: the contralateral inferior oblique Upshoots in Duane's retraction syndrome with inferior oblique overaction: ipsilateral Dissociated vertical deviation with inferior oblique overaction Other paralytic or restrictive conditions, and torsional Kestenbaum surgery
- The earliest surgery was done through a skin approach by Bonnet in 1841 The conjunctival approach is now chosen Limbal, paralimbal or fornix-based incisions may all be used The author prefers the fornix incision It gives good visualisation of the muscle without disturbing the tissues It also allows lateral rectus surgery in the same field if required
- After the lateral limbal or temporal fornix incision, hook the lateral rectus Dissect the intermuscular septum in the inferotemporal quadrant and retract the globe superonasally The anterior edge of inferior oblique is seen running towards the underside of lateral rectus Pass a blunt hook to lift the muscle until the posterior edge is visible from underneath Perforate the intermuscular septum behind the muscle and dissect the fascia between it and lateral rectus Disinsert with tenotomy scissors under direct vision and pass a 6-0 vicryl suture at each cut end
- A point 6 mm inferior and 6 mm posterior to the inferior end of the lateral rectus insertion That point is the anterior point of insertion for an 8 mm recession The posterior point lies 5-6 mm behind the anterior point in the same meridian For a 10 mm recession, the anterior point moves 2 mm down along the course of the muscle A 2 mm upward move instead gives a 6 mm recession The muscle is reattached along its original course, slackening it without anteropositioning
- A point 2 mm lateral and 3 mm posterior to the lateral end of the inferior rectus insertion That point gives a recession of about 10 mm The posterior point lies 5 mm behind it In addition to recession, this method has a slight anteropositioning effect
- The anterior end of the muscle is positioned at the lateral end of the inferior rectus insertion The posterior end lies further down: 5 mm posterior along the lateral border of inferior rectus That posterior placement is the author's modification This recesses and also anteropositions the muscle It severely weakens the elevator and the abduction in downgaze For more effect the anterior end may be inserted 1-2 mm anterior to the lateral end of inferior rectus
- Described from the author's centre by Prakash, Gupta and Sharma in 1994 The muscle is reinserted just adjacent to the inferior edge of the lateral rectus Its anterior end sits at the inferior end of the lateral rectus insertion This anteropositions without producing recession; a 1.5-2 mm recession counters the resection effect Weakening comes from anteropositioning, affecting elevation and abduction in upgaze Comparable to an 8 mm Fink's recession, but it does not change torsional status
- The entire width of the inferior oblique is reinserted anterior to the inferior rectus This weakens the elevator function almost totally Some depressor action may even be produced Lockwood's ligament acts as the new functional origin of the muscle The muscle then runs parallel to the inferior rectus Advocated for dissociated vertical deviation with inferior oblique overaction
- Controlled weakening procedures on the inferior oblique
- The hooked muscle is clamped between two artery clamps for 1-2 minutes The muscle is then cut with tenotomy scissors between the clamps It may bleed, and some surgeons cauterise the cut ends The author considers it a very traumatic procedure It cannot be undone and can give unpredictable results The effect cannot be graduated as it can with recession, so it appears obsolete
- The nerve to inferior oblique is a fusiform structure on the posterior border of the muscle It can be hooked and stroked to identify a tight band, which is cauterised This results in laxity of the muscle The muscle is then disinserted and the entire mass extirpated Reserved for overaction persisting despite maximal recession or myectomy
- The anterior half of the fibres is separately hooked and split for 12-14 mm, then recessed This selectively weakens extorsion Elevator and abductor function are unaffected Combined with advancement of the anterior fibres of the ipsilateral superior oblique The fellow eye receives a matching strengthening and weakening of the anterior fibres This combination constitutes torsional Kestenbaum surgery
- Strengthening procedures on the inferior oblique are limited It lacks a tendinous portion, so resection cannot be done A resection would in fact be a myectomy and would weaken the muscle Double breasting has been tried and found successful For selective strengthening, the anterior half or the entire width is disinserted It is then advanced 8 mm upwards from its actual insertion
- A-pattern deviations with overacting superior obliques: both superior obliques Brown's syndrome with overacting superior oblique, that is Brown's plus: unilateral As part of torsional Kestenbaum surgery, in a recession-advancement of all four obliques
- It has a long tendon and its functional origin is the trochlea, running anterior to posterior It has a fan-shaped insertion under the superior rectus Nasal to the superior rectus the fascia around it has no distinct sheath Dissection in that area should involve as little surgical manipulation as possible This prevents postoperative adhesions It is much safer to operate from the temporal side
- The surgeon sits on the side of the patient, looking towards the upper fornix The author's choice of conjunctival incision is superior limbal Fornix and paralimbal incisions are the alternatives The temporal approach lifts the superior limbal flap and hooks superior rectus from the temporal side The superotemporal quadrant is dissected, cutting the intermuscular septum temporal to superior rectus Glistening fibres of the superior oblique appear after the superior rectus is retracted nasally
- For tenotomy the tendon is disinserted at its insertion, full width, and left to retract Results are very unpredictable, as the free end reattaches at any point In tenectomy a part of the tendon is cut between two haemostats After identifying and hooking the muscle, tenectomy may be done nasal to the superior rectus Both cause generalised weakening of all functions, including torsion
- After hooking the superior oblique, the anterior 1-2 mm width of fibres is spared A wedge of the posterior fibres is excised This selectively weakens depression and abduction in downgaze It corrects the pattern deviation Intorsion is not significantly affected
- After disinserting the tendon it is reinserted 4 mm nasal to the superior rectus Inserting it close to the nasal border of superior rectus gives less weakening effect Prieto-Diaz suggested a translational recession: 12 mm from limbus and 6 mm from the nasal end of superior rectus Translational recession is intended to prevent limitation of depression in abduction That limitation is usually seen with anterior placement of the superior oblique
- A selective recession of the anterior half width can be done It weakens intorsion alone Depression and abduction in downgaze are not affected It forms part of the torsional Kestenbaum surgery
- After a superior limbal incision, or a paralimbal incision, the superior rectus is hooked Nasal intermuscular septum is dissected minimally, just button-holing near the nasal end of insertion A small blunt Steven's hook picks up the glistening band of superior oblique For tenotomy or tenectomy the tendon is transected after bringing it out of its fascial sheath Minimal manipulation is essential because there is no distinct sheath nasally
- Before transection, two double-armed 5-0 mersilene sutures are passed 2 mm apart The temporal suture lies 3-4 mm nasal to the nasal border of the superior rectus After transection a silicon band 2 or 2.5 mm wide and 5-8 mm long is interposed between the cut ends Minimally disturb the adjoining fascia to prevent postoperative adhesions It is preferably done through the temporal approach It maintains the fan-shaped insertion; the disadvantage is the risk of adhesions
- Weakening procedures on the superior oblique
- Tucking, or tenoplication, is the favoured generalised strengthening procedure It may be done from the temporal or nasal approach; the temporal is preferred Exercise restraint with frugal tissue handling to prevent an iatrogenic Brown's syndrome A tendon tucker may be used, or a combination of a hook and a resection clamp The tendon is hooked, lifted to double fold on itself, and a resection clamp applied A 4 plus 4 mm double folding gives an 8 mm tuck, enough for a 3-plus superior oblique underaction
- After double folding, tuck and suture the loop temporally, towards the insertion This prevents mechanical obstruction Perform an exaggerated forced duction test for superior oblique tightness after tucking It should confirm the absence of a tight superior oblique The inferior limbus should be able to rise past the horizontal line joining the two canthi
- Harada-Ito and its modifications selectively strengthen intorsion An anterior tenting of the anterior fibres with a non-absorbable suture achieves this The suture is passed close to the temporal end of the superior rectus The anterior fibres may instead be advanced towards the lateral rectus, 6-8 mm temporal to superior rectus It may be done as an adjustable procedure, as described by Metz Indicated in superior oblique paresis where the intorsion defect is the main complaint
- Strengthening procedures on the superior oblique
- The modern approach is to perform controlled and regulated procedures Torsional effect can be selectively weakened or strengthened So can the elevator or depressor effect with abduction in upgaze or downgaze This allows correction of V or A patterns without disturbing torsion Generalised procedures affect all functions of the oblique together Selective procedures exploit the fan-shaped insertion of the obliques
- Medial periosteal fixation is used in third nerve palsy The medial periosteum is exposed through a DCR incision or a retrocaruncular approach A 5-0 mersilene suture is passed through it and brought to the medial rectus insertion A medial limbal incision is made; the globe is adducted to produce 5-8 prism dioptres of esotropia and tightened Lateral rectus periosteal fixation: the suture is passed through the lateral rectus, which is disinserted The lateral periosteum is exposed and the lateral rectus secured to it
- Maximal recession in adults: MR 6 mm, LR 8 mm; in small children 5.5 mm and 7 mm Minimal effective recession: MR 3 mm, LR 4 mm Maximal resection: MR 6 mm, LR 9 mm; minimal 3 mm and 4.5 mm Sclera at the insertion is 0.3 mm thick; leave a 0.5 mm stump and an 8-10 mm insertion width Faden distance: MR 12-14, LR 16-20, SR and IR 14-16 mm Vertical recti: 2-5 mm is usually enough; 8-9 mm only in fibrosis or dysthyroid disease
- Operate for the static angle, after full cycloplegic correction and amblyopia therapy Split the correction between two muscles rather than overloading one Prefer graded, reversible procedures over tenotomy, myotomy and myectomy Repeat the forced duction test at every stage to identify what is really restricting the eye Never combine both vertical recti with the lateral rectus in one sitting Preserve tissue planes: the next operation depends on them
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- Strabismus Simplified