SQUINT SURGERIES

1. Squint surgeries
Presenter: Dr Mahrukh Khan

2. INTRODUCTION
• The most common aims of surgery on the extraocular muscles are to
correct misalignment to improve appearance and if possibleto restore BSV.
• Surgery can also be used to reduce an abnormal head posture and to
expand or centralize a field of Binocular single vision
• First step in the management of childhood strabismus involvescorrection
of any significant refractive error and/or treatment of amblyopia. Once
maximal visual potential is reached in both eyes, any residual deviation
can be treated surgically

3. PROCEDURES
• Three main types of procedure are:
• Weakening to decrease the effective strength of action of a muscle.
• Strengthening, to enhance the pull of a muscle.
• Vector adjustment procedures that have the primary aim of altering the
direction of muscle action.

4. 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

5. • 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

6. • Identify if eccentric 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 .
• Anesthesia – GA - LA in adults – Sub tenon’s is preferred

7. PRELIMINARY STEPS
• Fixation of globe
• For Horizontal rectus – 6 or 12 o’ clock
• For Vertical rectus – 9 or 3 o’ clock
• For Inferior oblique muscle- 4 ½ o’ clock in left eye - 7 ½ o’ clock in right eye
• After fixing eyeball is rotated away from the muscle being operated
• Conjunctival INCISION TYPES
Fornix incision
Limbal incision
• Exposure and isolation of the muscle
• Planned surgical technique
• Ended with closure

8. 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
Limbal incision – Used for rectus muscle surgeries
Adv:
• very little dissection of Tenon’s capsule required
• Maintains normal anatomic relations
• Easy and quick

9. MUSCLE WEAKENING PROCEDURES

10. MUSCLE STRENGTHENING

11. Recession
moving a rectus muscle posterior to its original
insertion site and reattaching it to the sclera, the
length/tension curve of the muscle is changed.
This has the effect of “weakening” the muscle’s
effect on the globe.
• This weakening effect probably occurs because
of both a reduction in the distance between the
origin and new insertion of the muscle, and
changes in the relationship between Tenon’s
capsule, the intermuscular septum, and the rectus
muscle pulleys.

13. Standard Rectus Muscle Recession Technique
• Placing Suture Near the Muscle Insertion
TRANSVERSE PASS
• the rectus muscle is isolated on a muscle hook,
• a suture is placed in the muscle near its insertion into the
sclera.
• The suture should generally be placed no closer than 1 mm
from the muscle’s insertion into the sclera.
• A suture pass is started at the midpoint of the muscle and
placed half thickness through the muscle. This is referred to
as the transverse pass. The needle is allowed to exit at the
border of the muscle
• If the needle stays in place once its tip has exited the muscle,
it is in proper location. However, if the needle appears
unstable, it has most likely been passed full thickness through
the muscle
• The suture is then passed in the opposite direction starting in
the center of the muscle, so that the transverse pass crosses
the entire width of the muscle posterior to its insertion site
LOCKING SUTURE
• passes are made at the borders of the muscle near the
insertion.
• should incorporate at least 1mm of muscle to achieve a
secure muscle-suture union
• The needle is passed full thickness through the muscle from
the posterior to the anterior aspect of the muscle and behind
the transverse suture pass.
• . Care should be taken to pass the needle directly through the
muscle.
• After the suture is passed full thickness through the muscle,
the needle holder is passed through the suture loop, grasping
the needle and pulling it through the suture loop to create a
locking bite .

15. • DETACHMENT OF THE MUSCLE
FROM THE GLOBE
The muscle sutures are placed between the
index finger and thumb of the hand holding
the muscle hook
The surgeon independently lift the suture and
provide more space to safely cut the muscle
from its insertion site

16. • SECURING THE MUSCLE TO THE SCLERA
AT ITS NEW LOCATION
• Locking forceps are placed on the edges of the muscle stump
after the muscle has been detached from the sclera.
• The sclera is marked to identify the entrance site for the
upcoming needle pass where the new insertion site of the muscle
will be placed.
• The mark on the sclera is made by indenting the sclera at the
desired recession site using a caliper.
• The needle is then placed into the sclera at the previously marked
positions.
• The needle pass in the sclera should be a minimum of 2 mm in
length and 200 µm in depth
• . The first needle exits the sclera and is allowed to remain in place.
The second needle is then passed in a similar fashion. This
“crossed swords” technique allows the sutures to be passed in
close proximity to each other without the second needle pass
damaging the previously passed suture
• . The sutures are then pulled through the sclera in the direction
of their pass
• . The sutures are then tied and cut making certain that the muscle
remains in place at its new insertion site by maintaining anterior
traction on the sutures while they are being tied .
• The suture is then tied to bring the central portion of the
muscle up to its intended attachment site

17. Hang-Back Recession
Techniques
• Type of non adjustable suspension recession
technique
• Performed for up to 7 mm of recessions
• Comparatively safer and equally effective

19. Hemi Hang-Back Modifications
• hemi hang-back recession technique for
recessions larger than 8 mm.
• In this method, the suture needles are passed
through the sclera approximately half the distance
between the original insertion site and the desired
new recession position.
• As with the hang-back procedure, it is important
that the needles exit close to one another in a
crossswords configuration.
• The muscle is then brought up to this midpoint
and the remainder of the procedure is identical to
the standard hang-back method

21. Surgical dose
• The amount of recession or resection
performed for a given deviation depends
primarily on the size of the deviation.
• However, many other factors may be
considered in a given case including the
presence or absence of a duction
limitation, level of fusion, associated
central nervous system disease, results
of forced traction testing, history of
previous strabismus surgery, and
findings at surgery that could alter the
surgical plan such as abnormal anatomy.

22. Suggested surgical guidelines for
bilateral recession or resection surgery
to treat exotropia
Suggested surgical guidelines for
unilateral recession and resection
surgery to treat esotropia
Suggested surgical guidelines for unilateral
recession surgery to treat esotropia and
exotropia (rarely done )

23. • SPECIAL CONSIDERATIONS
MEDIAL RECTUS : -
the medial rectus muscle does not have any direct attachments to an adjacent oblique
muscle. Because of this, the medial rectus muscle is more difficult to retrieve should it be
lost at the time of surgery. Excessive dissection of the intermuscular membrane and muscle
capsule is discouraged, in part for this reason.
Limits : 3mm to 7 mm
RECESSION OF LATERAL RECTUS
• LR should be preferably hooked from the superior border side
• Close proximity of the inferior oblique insertion to the inferior border LR
• Limits: 5mm to 8-10 mm

24. RECESSION OF INFERIOR RECTUS
• The inferior rectus muscle has fascial attachments to
Lockwood’s ligament, the inferior orbital septum, and the
tarsus of the lower eyelid. Because of these attachments,
recession of the inferior rectus may produce retraction
of the lower eyelid
• the use of primary infratarsal lower eyelid retractor
lysis to prevent eyelid retraction after inferior rectus
muscle recession
• This technique prevented lower eyelid retraction even
with recessions of up to 10 mm
• Avoid injury to nerve to inferior oblique, which enters
the muscle just as it passes lateral border of IR muscle

25. • SUPERIOR RECTUS
• The superior oblique tendon passes inferior to the superior rectus muscle starting
approximately 5 mm posterior to the nasal border of the superior rectus muscle
insertion. It is important to avoid inadvertently hooking the superior oblique
tendon when the superior rectus muscle is initially hooked .

26. DISINSERTION
• Disinsertion (or myectomy) involves
detaching a muscle from its
insertion without reattachment.
• It is most commonly used
to weakenan overacting inferior
obliquemuscle,when the technique
is the same as for a
recession except that the
muscle is not sutured.
• Very occasionally, disinsertion
is performed on a severely
contracted rectus muscle.

27. Posterior fixation suture
 The principle of this (Faden) procedure
is to suture the muscle belly to
the sclera posteriorly so as to decrease
the pull of the muscle in its field of
action without affecting the eye in the
primary position.
 The Faden procedure may be used on the
medial rectus to reduce convergence in
a convergence excess esotropia and on
the superior rectus to treat dissociated
vertical deviation DVD.
 When treating DVD, the superior rectus
muscle may also be recessed.
 The belly of the muscle is then
anchored to the sclera with a non -
absorbablesuture about 12 mm behind its
insertion.

28. Resection of the Rectus
Muscles and other
“Strengthening”
Procedures

29. STRENGTHENING PROCEDURES
• 1. RESECTION
• 2. TUCKLING
• 3. ADVANCEMENT

30. RESECTION
• Resection shortens a muscle to enhance its effective pull. It is
suitableonly for a rectus muscle
• The muscle is exposed and two absorbable sutures inserted at a measured
distance behind its insertion.
• The muscle anterior to the sutures is excised and the cut end reattached to the
originalinsertion

31. • Tucking of a muscle or its tendon is usually confined to enhancement of the
action of the superior oblique muscle in congenital fourth nerve palsy.
• Advancement of the muscle nearer to the limbus can be used to enhance the
action of a previously recessed rectus muscle.

32. Technique of Rectus Muscle Resection
• Preparation of the Muscle for Resection
Once the rectus muscle has been isolated, the intermuscular membrane, muscle
capsule, and other fascial tissues are dissected to allow for suture placement posterior
to the insertion site of the muscle.

33. Resection of the Muscle
• A second large hook is placed between
the muscle and the sclera posterior to
the hook that has been used to isolate
the muscle insertion. A caliper is used
to mark the position of the posterior
limit of the resection
• A central safety knot is placed in the
muscle at the caliper mark
• Transverse passes are made, followed
by locking bites at the borders of the
muscle. A small straight hemostat is
placed anterior to the suture and the
posterior muscle hook removed.
• The muscle is then detached from its
insertion on the globe and the distal
portion of the muscle is excised.

34. Reattaching the Muscle to the Sclera
• The sutures are then passed through
the original insertion site of the muscle
and the remaining muscle pulled up to
the original insertion site.
• The surgical assistant may facilitate this
process by retracting the globe toward
the muscle using locking forceps
attached to the insertion site to reduce
the amount of tension placed on the
muscle during this step of the
procedure, or the hemostat may be
used to hold the muscle in position if it
has not yet been removed
• The sutures are then tied and trimmed.

36. SUPERIOR OBLIQUE STRENGTHENING
• SO can be functionally divided
into
• Anterior 1/3 – Intorsion
• Posterior 2/3 – Depression and
abduction
• Best accessed through fornix
incision –
• Mainly two procedures

37. Harada ito procedure
• Selective strengthening of the anterior fibers
of SO muscle
• considered responsible for torsional action of
SO
• Anterior and lateral displacement of the
anterior fibers
• enhances incyclotropic action
• corrects excyclotropia
• 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
Classic Harada-Ito procedure. A 5-0 Mersilene doublearmed
suture is passed around the anterior portion of the superior
oblique tendon.
The needles are passed 8 mm posterior to the insertion site of
the lateral rectus at its superior border. The suture is pulled
forward bringing the anterior portion of the tendon toward the
lateral rectus muscle

38. SUPERIOR OBLIQUE TUCK
• A tuck of the superior
oblique tendon is designed to
enhance all three functions
of the superior oblique
muscle.
• Identifying the Superior
Oblique Tendon
• Isolation of the Superior
Oblique Tendon
• Tucking of the Superior
Oblique Tendon
A small hook is passed drawn anteriorly as it is held against the sclera posterior to the
insertion of SO tendon The small hook is exchanged for a larger hook

39. TUCKING THE SUPERIOR OBLIQUE TENDON WITH TUCKING DEVICE
a. Tendon is engaged and desired size of the tuck dialled into the tucker
b. A non absorbable suture is passed through the tendon to plicate the tuck
c. Base of the tuck examined to ensure knot is tight
d. Tucked portion of the tendon can be sutured to the sclera if desired

40. TRANSPOSITION
• Transposition refers to the relocation of one or more extraocular muscles to substitute for
the action of an absent or severely deficient muscle.
• The most common indication is severe lateral rectus weakness due to acquired
sixth cranial nerve palsy
• A variety of techniques involving recti and oblique muscles have been described.
– Knapp ‘s procedure
- Jensen ‘s procedure
-Hummelsheim procedure

41. 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
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
HUMMELSHEIM’S
PROCEDURE
• It is a 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

42. ADJUSTABLE SUTURES
• Indications
• The results of strabismus surgery can be improved by the use of adjustable
suture techniques on the rectus muscles.
• These are particularly indicated when a precise outcome is essential and when
the results with more conventional procedures are likely to be unpredictable;
for example, acquired vertical deviations associated withthyroid myopathy or
following a blowout fracture of the floor
• Other indications include sixth nerve palsy, adult exotropia and re-
operations in which scarring of surrounding tissues may make the finaloutcome
unpredictable. The main contraindication is inability to tolerate postoperative suture
adjustment (e.g. young children).

43. • Operative procedure •
• The muscle is exposed, sutures inserted and the
tendon disinserted from the sclera as for a rectus
muscle recession.
• The two ends of the suture are passed, side
by side, through the stump ofthe insertion.
• second suture is knotted and tied tightly
around the muscle suture anterior to its
emergence from the stump
• one end of the suture is cut short
and the two endstied together to form
a loop
• The conjunctiva is left open.

44. BOTULINUM TOXIN
CHEMODENERVATION
• Temporary paralysis of an extraocular muscle can be induced by an injection
of botulinum toxin under topical anaesthesia and EMG control.
• The effect takes several days to develop, is usually maximal at 1–2weeks
following injection andhas generally worn off by 3 months.