EFFECT OF Muscle weakening
*Doesn’t cause limitation of movement (unless more than recommended maximum sx)
*Effect greatest in field of action
*Amount of recession depends on the muscle
*Recession is most common rectus muscle weakening procedure
OBLIQUE RECESSION
○ One side of muscle is recessed more than the other
TRANSPOSITION
Insertion of horizontal recti raised or lowered to weaken more in up-gaze or down-gaze
Augmented recessions
Loop recession
*Muscle maximally recessed and reattached by loop sutures through corners of tendon
*Useful in persistent ET
Hang- loose recession
*Muscle disinserted and reattached to its original insertion using extended sutures
Tenectomy/ tenotomy
Muscle weakened by complete or partial tenectomy or tendon space or expander
SO muscle - Browns, A pattern XT, Completed 3NP
Myectomy
Segment of muscle cut out and muscle is released to allow retraction back into tenons capsule
Myotomy
Used to augment effect of recession
Muscle lengthened by transverse incisions
Posterior fixation suture (faden procedure)
○ Produce progressive weakening as the eye moves into the field of action
○ Reduces lower arm action progressively
○ Only used on MR, SR, IR
USED IN LR PALSY, CONV EXCESS, INFANT ET C FT, DVD
Considerable experience needed to perform
Further weakening procedures for IO
- Extirpation
Disinsertion
Effect of Strengthening procedures
Muscles shortened and strengthened
Maintains its action through point of original insertion
Maximum amount of resection to avoid restrictions
Resection preferrable to advancement (muscle moved forwards towards limbus)
- More effective
- Muscle more visible through sclera
Cannot reverse resection
Never used in TED
More reaction post op than most surgery
Advancement only used on recessed muscle that has overcorrected angle
2 methods
1. Sutures woven through muscle belly and required distance
- Muscle in front cut off
- Shorter muscle reattached at original insertion
2. Muscle tendon grasped - Tendon cut close to globe - Sutures through tendon and muscle belly at required distance - Tied and anterior unused portion cut off
SO TUCK
- Strengthens muscle by folding termina muscle and tendon
- Muscle not disinserted
- Sutures through muscle belly at required point and passed through tendinous insertion, tightened and tied
- Rarely on rectus
- SO - advancement and resection tricky and unreliable
- Normally cant tuck SO more than 8mm
- Useful in SO palsy when HoT greatest in downgaze
- Great risk of causing iatrogenic browns syndrome
what is TRANSPOSITION surgery
Movement of part/ whole muscle(s) to alter its 1 or 2 degree action
Used in muscle paralysis or severe paresis
RECTUS MUSCLES ONLY (very rarely SO and IO)
Aim to realign deviating eye in PP
Movement in direction of paralysed muscle not greatly improved
WHOLE MUSCLE TRANSPOSITION
Horiz or vertical muscles transposed singly
IPSILATERAL PAIRS e.g. RLR and RMR - Rotate eye in direction of transposition - Transposed asymetrically to alter A and V patterns and correct cyclotorsion CONTRALATERAL PAIRS e.g. RMR, LLR - Contralateral pairs transposed symmetrically INDICATIONS - A + V patterns - transpose horiz recti, combined with recess/resect - Horiz transposition of vert recti - correct cyclotropia - LR paralysis - SR and IR transposed and lower poles of LR insertion - Duanes - type A - MR paralysis - Lost muscle Knapp - moving MR and LR adjacent to SR for elevation deficiency Inverse Knapp - moving MR and LR to IR for depression deficiency
PART MUSCLE TRANSPOSITION
- Only half of muscle is transposed, reducing risk of ant. Segment ischaemia
- Usually two muscles involved and transposed to a third
- Muscle paralysis - double elevator palsy - elderly px with poor blood supplyLR stabalisation
- Used for upshoot and downshoots in duanes retraction
- Prevents globe from slipping over ipsilateral LR on attempt ADD
- Jampolsky (1984) advised recession and splitting of LR, half of muscle above insertion, half below
SO TRANSPOSITION
Harada-ITO procedure
- Increases intorting action of SO without affecting depression and abduction - often in bilateral SO palsy
- Anterior 1/3 of SO tendon disinserted and split about 10mm up. Mobilised portion reattached 8mm posterior to LR insertion
Hummelsheim
- Lateral halves of uperior and inferior recti disinserted
- Medial and lateral fibres of each muscle are seperated posteriorly
- Lateral half reinserted alongside upper and lower poles of lateral rectus
Original hummelsheim - suture transposed section of muscle directly to LR muscle
Current method - suture transposed muscle to sclera adjacent to paralysed muscle
Augmented
- 5mm of tranposed muscle resected before suturing to sclera
Jensen
- Transposition without disinsertion
- Maintains ant segment blood supply
- 3 adjacent rectus muscles split in half along muscle fibres
- For LR - lateral halves of sup and inf tied loosely to upper and lower halves of split LR close to equator
· Aim to keep one ciliary vessel undisturbed in portion of each vertical rectus muscle not being transposed
· Nonabsorbable suture looped around adjacent muscle segments and tied
· Too tight - damage to the rectus muscles and blood supply
· Too loose – anterior migration of suture causing muscle slippage
Hummelshein vs Jenson
Biomechanical modelling (Lee et al. 2018)
Able to model different transposition surgeries on the same model eye with LR palsy
Hummelscheim 40.8% reduction in deviation (28^BO)
Jensen 49.4% reduction in deviation (34^BO)
