Surgery of the Extraocular Muscles Goals: • 1)To improve function and apperance • 2)To (may) relieve asthenopia and double vision • 4)To restore fusion and steropsisesp in intermittent cases. • 5)To treat abnormal head position. • 6) Shifting null point from periphery to a more centered location in nystagmus cases.
1368 84 cases
Planning Considerations Visual Acuity 1) Operation is preferred on the eye with low vision 2) In children 1st treat amblyopia 3) To be effective, restrictive forces must be relieved.
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.
Cyclovertical Strabismus • In general surgery should be performed on those muscles whose field of action corresponds to the greatest vertical deviation.
Eg: a patient with R-hypertropia that is greatest down and to the patient’s left.Preferred Operation is • 1) Strengthening the R.S.O muscle or • 2) weakening of the L- I.R muscle
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
R L • 1) LSR strengthening • 2) LIR recession or • 3)RIO weakening or • 4) RSO strengthening • May be chosen for operation
Prior Surgery • It is preferable to operate on muscles that have not undergone prior surgery except: If restriction resulted from prior surgery
Weakening procedures • Recessions: Hang-back recession or fixed recession • Marginal myotomy, Myotomy & Myectomy • TenatomyandTenectomy • Denervation and extirpation • Recession and anteriorization
Hang-back recession can be used reliably Reinserting sutures pass through the thicker stump of the original insertion with less risk of perforation
Marginal myotomy Cutting partway across a muscle usually following a maximal recession eg.Rectus muscle
Myectomy • Myectory by removal a portion of muscle eg IO myectomy
Tenatomy • cutting across a tendon like (so tenatomy)
Tenectomy • removing a portion of tendon (SO) • silicone spacer can be used.
Denervation and extirpation. • The ablation of the entire portion of the muscle along with its nerve supply within the tenon capsule (used only for recurrent IO overaction)
8) Recession and anteriorization: movement of the muscle’s insertion anterior to its original position used for DVD + IO overaction together
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.
Strengthening procedures • Resection
Advancement • toward the limbus used in previously recessed muscle with overcorrection.
Tucking Usually used for superior oblique tendon
Techniques of surgery • Fixed suture • Adjustable suture
Adjustable suture Position of the muscle can be altered during the early post operative days.
Spring1376 120 Cases
Pull-over sutures Fixing the eye in a selected position during post-op healing for 10-14 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.
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.
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.
Esodeviation Max 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> 40 Max MR resection 6mm for deviation> 40∆ Most surgeons prefer recession over resection procedure as a first operation.
Value of immediate overcorrection in exodeviation Small to moderate overcorrection of exotropia in the early posoperative period has most favorable long term result.
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.
Weakening the superior oblique muscle include: Tenotomy Tenectomy Z-lengthening Placement of spacer (of silicone), fascia lata or non absorbable suture loops between the cut ends of the tendons to functionally lengthen it and recession.
Disadvantage of spacer Possible adhesion formation which can alter motility.
Treatment of severe globe retraction • May be helped by recessions of both MR and LR • For 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.
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.
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.
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.