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Strabismus 106 > Basic Principles of Surgical Management > Flashcards

Basic Principles of Surgical Management Flashcards

1
Q

What are the aims of strabismus surgery?

A
  • Restore binocular single vision (BSV)
  • Expand and/or centralise field of BSV
  • Improve ocular appearance
    Prevent/improve psychosocial problems
  • Restore concomitance
    Incomitant strabismus and alphabet patterns
  • Relieve symptoms
  • Improve visual acuity
  • Overcome need for an abnormal head posture (AHP)
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2
Q

What must be left undisturbed during strabismus surgery?

A
  • Orbital fat must be left undisturbed
  • Vortex vein should be avoided
  • Lockwood’s ligament (suspensory ligament of the eyeball) supports lower lid position, IO and IR-muscles - damage to this can affect lid position. It stretches below the eyeball between the medial and lateral check ligaments and enclosing the inferior rectus and inferior obliquemusclesof theeye.
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3
Q

What is Tenon’s capsule also known as?

A

Bulbar Fascia

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4
Q

What & where is Tenon’s Capsule/Bulbar Fascia?

A

Tenon’s capsule (Bulbar Fascia) lies beneath the conjunctiva and extends from the optic nerve to the limbus as a fascial layer that envelops the extraocular muscles and separates the orbital fat into intraconal and extraconal compartments.

It forms a capsule around the muscles and the intermuscular septum connecting the EOMs. Within Tenon’s capsule there is dense connecting tissue

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5
Q

What is the Spiral of Tillaux?

A

Beginning with the medial rectus and moving inferiorly and temporally, each rectus muscle inserts further from the limbus. This is called the spiral of Tillaux.

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6
Q

What can cause issues when operating on the inferior rectus muscle?

A

The attachment of the ligament of Lockwood to the lower lid can cause problems when operating on the inferior rectus muscle, so the muscle should be freed from the ligament as much as possible

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7
Q

How does the inferior oblique penetrate the tenon’s capsule?

A

It penetrates tenon’s capsule beneath the inferior muscle and forms part of the ligament of Lockwood. Its insertion lies under the lateral rectus muscle as far back as the macular area.

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8
Q

What surgery should be done on the inferior oblique?

A

Because of its relationships a disinsertion, myectomy, recession or antero-position may be carried out without crippling the muscle.

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9
Q

How does the superior oblique penetrate tenon’s capsule?

A

Penetrates tenon’s capsule 3mm nasal to the medial border of the superior rectus muscle. It has a fan-shaped insertion.

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10
Q

Where is the tendon sheath in relation to the superior oblique?

A

The tendon sheath surrounds the muscle 10mm before the trochlear as far as it’s insertion and connects to the superior rectus sheath, which needs to be disconnected during surgery.

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11
Q

What are extraocular muscle pulleys?

A

Complex arrangement of connective tissue between extraocular muscles (EOM), Tenon’s capsule, the globe and the orbit

Connective tissue made up of collagen fibres that encircle and interconnect EOMs

Collagen sleeves and elastin bands surrounding EOMs between the equator of the globe and optic nerve junction = Extraocular muscle pulleys

There are also dense condensations of collagen and elastin bands surrounding the extraocular muscles between the equator of the globe and the globe– optic nerve junction; these act as a sleeve around the rectus muscles and the inferior oblique muscle. These areas are known as extraocular muscle pulleys

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12
Q

How does the inferior oblique move in elevation and in depression?

A

The inferior oblique (IO) moves anteriorly on elevation and posteriorly in depression. The global layer (GL) of an EOM passes through the pulley. For the inferior rectus (IR) the GL contracts modestly in depression. The orbital layer of the IO inserts directly into the sleeve and positioned more posterior

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13
Q

What do we have to consider when making a choice of surgical procedure?

A
  • Type and size of the strabismus
  • Age of patient
  • Anatomical factors
  • State of muscle and any previous surgery (the muscle can become fibrose i.e. tighter)
  • Visual acuity
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14
Q

What tests do we have to do to inform the type and amount of surgery?

A

Pre-operative assessment
- Visual Acuity
- Cover test
- Ocular Movements
- Convergence
- Measurement
- State of Correspondence
- Assessment of Binocular Function
- Measurement of AC/A ratio (if appropriate)
- Post-operative diplopia test

Results of the above should inform type and amount of surgery

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15
Q

What are the 3 types of surgical procedure?

A
  • Recession (weakening)
  • Resection (Strengthening)
  • Transposition (Transposing)

Combining weakening of agonist with strengthening of ipsilateral antagonist result in greater correction (effect)

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16
Q

What tests do we have to do for a surgical plan?

A

Pre-operative assessment
- Potential for BSV/ restore BSV
- Risk of post-op diplopia
- Surgeon and patient expectations
- Two stage surgery

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17
Q

What are the aims of strabismus surgery?

A

1) To restore parallelism of the visual axes in functional squints with a good prognosis for B.S.V. including:
constant manifest squints with demonstrable binocular function
intermittent manifest squints

2) To relieve symptoms due to effort to control a deviation e.g. decompensating heterophorias
3) To restore concomitance in paralytic squint / A/V patterns

4) To overcome a need for an abnormal head posture

5) To improve visual acuity e.g. nystagmus

6) To restore a good ocular alignment

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18
Q

Why might a surgery be split into more than one operation?

A

Although it is preferable to correct the squint with one operation it may have to be carried out in stages e.g.

a) If surgery needed on more than two rectus muscles of the same eye with a risk of anterior segment ischaemia

b) Complex deviation

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19
Q

What do recession, resection or transposition surgery do?

A
  • Weakening procedure: reduce the action of the EOM
  • Strengthening procedure: enhance the action of the EOM (most common)
  • Transposing procedure: alter the direction of action of EOM/ the muscle’s line of action is changed, can make it an elevator for example, to give it other functions.
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20
Q

What’s the most common surgical procedure?

A

Resection

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21
Q

What are the types of recession procedures?

A
  • Conjunctival recessions
  • Augmented recessions
    + Loop recessions
    +Hang-loose recessions
  • Posterior fixation suture (Faden Operation)

Most common in weakening procedures for concomitant and incomitant strabismus

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22
Q

What surgeries do we do on the oblique muscles?

A

We work on the tendon or muscle;

  • Myotomy / Tenotomy
  • Myectomy / Tenectomy
  • IO disinsertion
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23
Q

How is a Lateral Rectus Recession carried out?

A
  • Make an incision in the conjunctiva
  • The muscle is isolated and captured
  • The globe is rotated away from the muscle by placing tension on the limbal stay sutures. The muscle hook can now be retracted 2–3mm from the muscle insertion to expose the tendon.
  • Sutures are placed in the muscle margin 1mm posterior to the tendinous insertion of the exposed muscle.
  • The muscle is detached by transecting the tendon as close to its insertion as possible. This minimises bleeding, makes the recession measurements more accurate.
  • The desired amount of recession is measured out in millimetres using callipers directed posteriorly from both ends of the original insertion; the sclera is marked at the intended reinsertion points.
  • The rectus tendon is reinserted parallel to its original attachment.
  • To facilitate the new insertion lying parallel to the original attachment one end of the insertion should be secured first; tension can now be applied to the remaining suture to determine its appropriate point of attachment.
  • The conjunctiva is closed using 7.0 Vicryl.
24
Q

How much of a recession do we do (mix & max) for each EOM?

A

EOM –> Min –> Max –> Super-Max

MR –> 3mm –> 6mm –> 7-8mm

LR –> 5mm –> Children 7mm, Adults 9mm –> 10mm

SR –> 2.5mm –> 4mm –> 10-14mm

IR –> 2.5mm –> 4mm

IO –> 10mm Max

SO –> 8mm Max (rare)

25
Q

What’s the hang-back ‘hang loose’ recession?

A

Use extended absorbable or non-absorbable sutures of predetermined length.

Enable extensive (super-maximal) recession

26
Q

How is hang-back ‘hang loose’ recession done?

A

The muscle is disinserted and reattached to the original insertion using non-absorbable sutures of a predetermined length

27
Q

What are the indications of a hang-back ‘hang loose’ recession?

A

Indications:
- When maximum recession gives inadequate correction e.g. infantile esotropia/ convergence excess

  • When reoperations on previously recessed muscles is required
28
Q

What are Augmented Recessions?

A

Aim-
To increase the weakening effect of recessions beyond the conventional amount without causing limitation of movement.
The effect of the basic recession is augmented (increased) using Loop Sutures

Principle-
Provided the insertion of a rectus muscle remains at or in front of the point tangential to the globe’s surface, the muscle can be slackened without limiting movement

29
Q

What are loop recessions?

A

A maximum recession is performed, then the muscle is re-attached to the globe by non-absorbable loop sutures, tied around a metal rod, the size of the loop can be graded by use of various diameter rods.

30
Q

What’s the Faden procedure also known as?

A

Posterior Fixation Suture

31
Q

What is the Faden/Posterior Fixation Suture?

A

Aim:
Produce progressive weakening as the eye moves into the field of action of the operated rectus muscle

Principle:
The suture is positioned posterior to the muscle insertion, the further the eye move into the main action of the muscle, the weakening effect increases
There is less weakening effect in primary position

Technique:
Can be combined with and without recession

32
Q

What is the method of the Faden (Posterior Fixation Suture)?

A

The muscle is disinserted from the insertion, non dissolvable sutures are placed through the muscle onto the sclera at 10-14mm behind the insertion. The muscle tendon is then replaced onto insertion, or combined with a recession of the muscle.
The effect of the faden operation is similar to that of augmented recessions, but mechanical limitation of movement is less because muscle slackness is avoided.

33
Q

What’s an indication of using the Faden (Posterior Fixation Suture)?

A
  • Nystagmus block syndrome
  • Convergence excess esotropia
  • DVD
  • Duanes retraction syndrome
  • L.R. palsy ( contralateral M.R.)
  • Blowout fracture / Dysthyroid eye disease (S.R. of normal eye)
  • Nystagmus with null point
34
Q

What are the advantages and disadvantages of the Faden procedure?

A

Advantages
- Gaze into opposite direction not affected
- No disruption to blood supply
- No change of deviation in primary position
- Predictable results
- Avoids secondary contracture

Disadvantages
- Technically difficult to carry out
- Difficult procedure to reverse due to fibrosis with time

35
Q

What options do we have to weaken the Inferior Oblique?

A
  • Recession
  • Myectomy
  • Myotomy
  • Disinsertion
  • Anterior transposition
36
Q

What is a Myectomy?

A

Aim:
Produce an uncontrolled weakening of the IO. Only ever performed on the inferior oblique muscle.

The IO is captured and a second squint hook passed in the same plane as the first to spread the muscle belly and facilitate separating it from its fascial sheath midway between its insertion and the lateral border of the inferior rectus.

The muscle is crushed with haemostatic forceps held 6–8mm apart and the portion between the forceps is removed.

The incisions in Tenon’s capsule and conjunctiva are then closed

Must take care not to damage the infero-temporal vortex vein

37
Q

Why might a myectomy be
better than a recession? What are the disadvantages?

A

Advantages of Myectomy over recession
- The macula is safeguarded
- It is a simple procedure and works well in patients with good fusion e,g, acquired S.O. palsy
- The scar is inferior and temporal so not easily seen

Disadvantages
- Gives an unpredictable amount of correction
- Can produce an adhesive syndrome
- Anomalies of the insertion may be missed
- It cannot be put back if overcorrected

38
Q

What is a Myotomy?

A

Transverse cuts in the IO muscle, can be several cuts at the 2 borders of the IO muscle

To elongate the muscle

Cutting through the muscle is now rarely used since it was very unpredictable and muscle adhesions may still be brought about by intermuscular connections and check ligaments.
Marginal myotomy is preferred

39
Q

When is a Myotomy indicated?

A
  • As further weakening following a full recession
  • Combined with recession to obtain a double weakening effect but maintain arc of contact
  • Where the sclera is extremely thin
40
Q

How do we carry out an IO disinsertion?

A

The IO muscle is pulled nasally and the muscle fascia and insertion identified.

The IO is divided at the insertion and cautery is applied to any bleeding points.

The conjunctival incision is closed.

Outcome:
Division at the muscle insertion leads to a permanent and effective weakening

41
Q

What is a Tenectomy?

A

Tenectomy
- A section of tendon is removed
- Only performed on the superior oblique muscle, can be approached nasally or temporally to the superior rectus muscle. It may cause torsion.

Indications
Brown’s syndrome, A exo pattern

42
Q

What is a Tenotomy?

A

Tenotomy
- Cutting through the tendon
- The nearer to the trochlea the tenotomy is performed the greater its effect.

Cutting through tendon, mainly reserved for superior oblique weakening. The nearer to the trochlea the tenotomy is performed the greater its effect.

Partial tenotomy -
Used on superior oblique muscle for an A exo pattern to reduce abducting action by disinserting the posterior portion of the insertion.

Intrasheath tenotomy -
Used to treat Brown’s syndrome.

43
Q

What’s an adjustable suture?

A

Enables immediate post-operative adjustment

Performed under local anaesthetic

Require co-operative patient

Most commonly used for recessions
Can also be used in resection and transposition procedures

An Orthoptist commonly performs the Cover Test, measurement of deviation, assess binocular status and presence of diplopia

44
Q

What’s a Jampolsky type of adjustable suture?

A

Recessed muscle is sutured to the globe in such a way that the sutures can be loosened and muscle tendon pulled forwards or retracted backwards during adjustment

Bow-tie knot

45
Q

What’s the Fells type of Adjustable Suture Technique?

A

Sliding Noose

The muscle is secured to the sclera through the insertion, but the muscle suture itself is not tied down immediately. Instead, a surgical tie, typically consisting of the same material used for the muscle suture, is passed around the muscle suture and tied squarely down. Despite the surgical tie being tied securely around the muscle suture, it is able to slide freely along the length of muscle suture with effort.

46
Q

What are the aims of surgical strengthening procedures?

A

Aim:
Strengthen the action of the muscle

Resection
- Shorten the muscle

Advancement
- Advancement of the line of insertion towards the limbus
- Mainly performed in re-operations

Tuck/Plication
- SO tuck (folding the tendon) to make it shorter

47
Q

What is the Tuck/Plication principle & method?

A

a) Principle -
This is performed on the superior oblique muscle, a tuck is made into the muscle.

b) Method -
The tendon is exposed either nasally or temporally to the superior rectus muscle, nasally avoids the superior nasal vortex vein but can cause pseudo Brown’s syndrome.

The tendon is taken up with a tendon tucker until resistance is felt in the tendon. It is sutured together and folded over laterally and sutured again with non dissolvable sutures. This will increase all the actions of the superior oblique.

48
Q

What are the advantages and disadvantages of Tuck/Plication?

A

Advantages
Effective in improving depression of the eye and counteracting excyclotorsion

Disadvantages
It may come undone
It may cause a temporary or permanent inability to elevate the adducted eye e.g Brown’s syndrome

49
Q

What is the method of a Resection?

A

The muscle is isolated and sufficient dissection of muscle fascia to allow safe and secure suture placement.

The muscle is secured using sutures with one double and one single throw.

The portion of muscle in front of the sutures is excised.

The shortened muscle is reattached and secured to the sclera.

One end of the insertion should be secured first; tension can now be applied to the remaining suture to determine its appropriate point of attachment.

The conjunctiva is closed

50
Q

What are the advantages and disadvantages of a resection?

A

Advantages
- It can be used on any rectus muscle
- It is predictable

Disadvantages
- It is irreversible
- It causes more reaction in the eye than a recession
- It should be combined with a recession for maximum effect
It is of no use in a completely paresed muscle

51
Q

How much Resection should we do the recti muscles?

A

EOM –> Min –> Max

MR –> 5mm –> 6mm

LR –> 8mm Max

SR –> 2.5mm –> 4mm

IR –> 6mm Max

52
Q

In horizontal squints when might we conduct bilateral surgery?

A

The medial recti are more effective for near and the lateral recti for distance so if there is a large difference in the angle between near and distance may operate bilaterally

53
Q

In horizontal squints when might we conduct unilateral surgery?

A

This is usually performed when there is no great difference between near and distance measurements i.e. 2 muscles on one eye.

54
Q

In horizontal squints when might we conduct functional/cosmetic surgery?

A

With a cosmetic case the surgeon aims to leave the eyes slightly convergent as the eyes tend to diverge with time

In a functional case the surgeon tries to correct the exact amount to align the visual axes although this may vary depending on the type of squint and the surgeon

55
Q

What can affect choice of surgical procedure?

A

Type of horizontal squint

Size of deviation
* A greater effect is achieved if 2 muscles are operated on at the same time
* A very small squint may only require 1 muscle to be operated on but this often has little effect
* If more than one procedure is required it may be better to perform unilateral rather than bilateral surgery

Visual acuity
Surgeon’s tend to operate on the eye with the poorest vision, in case any problems do occur

State of the muscles / previous surgery
If a patient has had previous surgery or congenital problems with certain muscles there may be no point in operating on these muscles

Anatomical factors
Some muscles are easier to operate on than other muscles due to their anatomical placing

Age of patient
Adult eyes may require a larger amount of surgery than children as surgery is more effective on a child than an adult as muscle tone is better

56
Q

What post-operative complications occur?

A
  • Infections
  • Orbital cellulitis - This is very rare
  • Suture reaction
  • Granulomas - occur 2-3 weeks post-operatively. it often disappears but sometimes needs topical steroids and excising
  • Conjunctival cysts - may need excising
  • Prolapse of Tenon’s capsule - usually caused by incomplete conjunctival closure, commonly shrinks back into wound, otherwise may need excising
  • Lost or slipped muscle, immediate return to the operating theatre
  • Post-operative diplopia - often disappears spontaneously, otherwise may need orthoptic intervention
57
Q

What is the post-op role of the orthoptist?

A

Adjustable sutures
-Cover test and measurements
- Binocular status/ diplopia

Post-operative assessment
- Cover Test
- Measurement
- Assessment of binocular function / diplopia
- Assessment of Alignment
- Ocular Movements

The above should inform the success of treatment and any further treatment required

Strabismus 106 (35 decks)

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