7 Surgery of the Extraocular Muscles Goals:1)To improve function and apperance2)To (may) relieve asthenopia and double vision4)To restore fusion and steropsis esp in intermittent cases.5)To treat abnormal head position.6) Shifting null point from periphery to a more centered location in nystagmus cases.
9 Planning Considerations Visual Acuity1) Operation is preferred on the eye with low vision2) In children 1st treat amblyopia3) To be effective, restrictive forces must be relieved.
10 Distance-near incomitance In cases of horizontal distance-near incomitance it has been suggested muscles responsible, be operated on for horizontal deviations.2) Recent evidence suggests that it may be of minor importance.
12 Cyclovertical Strabismus In general surgery should be performed on those muscles whose field of action corresponds to the greatest vertical deviation.
13 1) Strengthening the R.S.O muscle or 2) weakening of the L- I.R muscle Eg: a patient with R-hypertropia that is greatest down and to the patient’s left. Preferred Operation is1) Strengthening the R.S.O muscle or2) weakening of the L- I.R muscle25108301220Max40 Rht
14 If the R hypertropia is the same in L-upgaze, stright left & L- down gaze then any of the 4 muscles whose greatest vertical action is in left gaze may be chosen for surgery
15 May be chosen for operation L15∆ RHT1) LSR strengthening2) LIR recession or3) RIO weakening or4) RSO strengtheningMay be chosen for operation
28 9) Post fixation suture (Faden operation) Attachment of rectus muscle to the sclera 11-18mm post to the insertion using a nonabsorbable suture, fixation to the muscle’s pulley may be safer used in DVD, nystagmus, high AC/A esotropia and non-comitant strabismus.
37 Pull-over suturesFixing the eye in a selected position during post-op healing for days. Used in severely restricted rotations. A temporary suture is attached to the sclera at the limbus or under a rectus muscle insertion brought out through the eyelids and secured to periocular skin over a bloster to fix the eye in selected desired position.
38 Transposition porocedure Employed most often for treatment of paralytic strabismus or with small A and V pattern, Duane syndrome and monoocular elevation deficiency.Vertical deviations are an occasional complication of transposition, requiring additional operation.
39 Guidelines for strabismus surgery Any two surgeons are unlikely to perform a specific surgical procedure in exactly the same way.Each surgeon must refine his or her approach by continually reviewing the results and adjusting the amounts of surgery to achieve the best possible outcomes.
40 EsodeviationMax MR recession 7mm for 60∆-80∆ , 3-4 muscles is preferred.Max LR resection 9mm for 50∆Max LR recession 9mm or greater for deviation> 40Max MR resection 6mm for deviation> 40∆Most surgeons prefer recession over resection procedure as a first operation.
43 Value of immediate overcorrection in exodeviation Small to moderate overcorrection of exotropia in the early posoperative period has most favorable long term result.
44 Inf oblique muscle weakening procedures If there is bilateral asymmetric overaction and no S.O paralysis, bilateral IO weakening is recommended. Weakening of IO could correct up to 15∆ of vertical deviation in primary position.
45 Weakening the superior oblique muscle include: TenotomyTenectomyZ-lengtheningPlacement of spacer (of silicone), fascia lata or non absorbable suture loops between the cut ends of the tendons to functionally lengthen it and recession.
46 Disadvantage of spacer Possible adhesion formation which can alter motility.
47 Treatment of severe globe retraction May be helped by recessions ofboth MR and LRFor upshoot or downshoot are splitting the lateral rectus muscle in a Y configuration, a posterior fixation procedure on this muscle, and more recently, distinction of the lateral rectus muscle and reattachment to the the lateral wall of orbit.
48 Unilateral or bilateral S.O weakening Unilateral is not commonly performed except as the treatment for Brown syndrome.Or for an isolated IO weakness which is rare.
49 Many ophthalmologists favor a tenotomy of just the posterior 75%-80% of the tendon toward its distal end to leave the torsional action, which is controlled by the most anterior tendon fibers , intact.
50 Bilateral weakening of S.O In A pattern can lead to an eso shift of up to 40∆ in downgaze and a variable change in primary position and almost no change in upgaze.
51 Oblique muscle tightening (strengthening) procedure IO tightening is very infrequent. To be effective advancement of the Io muscle requires reinsertion more posteriorly and superiorly which is difficult and exposes the muscle to possible injury.
53 Tightening of the S.O muscle Tucking should be performed on the distal portion of the tendon to avoid producing an iatrogenic Brown synd.
54 Harda-Ito rocedureIs designed to primarilly affect torsion.
55 Harada-Ito procedureto reduce excyclotorsion in patients with sup oblique muscle paralysis the anterior half of the sup oblique tendon advanced temporaly and somewhat closer to the limbus.
56 Pure comitant vertical deviation Recessions of vertical rectus muscle are preferred as a 1st procedure.
57 Comitant Vertical deviation< 10∆ with horizontal deviations R&R plus reinsection by about one-half the tendon width (up or down as appropriate) is effective.SO R&R + displacement up or down is selected rather than doing symmetrical operation.
59 So R&R + displacement up or down is selected rather than doing symmetrical operation.
60 DVDHang-back suture of 6-10mm is effective (without reattachment to sclera)Faden operation (or post fixation suture on S.R muscles) often combined with recession.Resection of IR (4-8mm) may advance the lower eyelid margin upward. Especially if careful dissection is not performed.
61 4) If DVD with Inf oblique overaction is present: Moving the insertion of IO muscles anteriorly to a point adjacent to the lateral border of IR (anterior transposition) can cause elevation def in abduction. (anti elevation syndrome) if reattached to lat corner of the muscle at or anterior to the spiral of Tillax.
62 Transposition procedures Involve the risk of ant segment ischemia if antagonist muscle recession is added. Augmentation is done by resecting the transposed muscle or by employing the Foster modification.
66 Complication of strabismius surgery Unsatisfactory alignmentAlignment in the immediate postoperative period, whether or not satisfactory, may not be permanent. This can be due to poor fusion, poor vision and contracture of scar tissue. Reoperation are often necessary.
67 Refractive changes Changes in refractive error are most common when Strabismus surgery is performed on 2 rectus muscles of one eye.An induced astigmatism of low magnitude usually resolves within a few months.
68 Diplopia Usually seen in older children and especially in adults. Prolonged post operative diplopia is uncommon.Prisms that compensate the deviation may be helpful the risk of bothersome post op diplopia if severe and persists more than 4-6 weeks. A temporary prisms should be tried or botulinum toxin injection can be used.
69 Perforation of the sclera Needle may perforate in to the suprachoroidal space or through the choroid and retina. In most cases this results in only a small chorioretinal scar with no effect on vision.