Consecutive Esotropia (ET) Flashcards
What’s more common, spontaneous consecutive XT or spontaneous consecutive ET?
Spontaneous Consecutive XT is more common than Consecutive ET
What is a consecutive ET?
Esotropia in a patient who previously had an exotropia or exophoria
What are the three ways that consecutive ET can occur?
Post-operative - typical
Optical – possible – if becoming more myopic a myopic prescription can create an ET
Spontaneous - rare
How might a minus lens lead to an ET or E?
Minus lens therapy (additional minus lenses) – overminus – induces accommodation which also induces convergence (AC/A ratio) = ET or E induced
Myopic eyes tend to be larger than Hypermetropic eyes so there looks like there is crowding at the optic nerve
How is DvD associated with consecutive XT?
Mein (1981) found that in spontaneous ET (rare) that early onset XT who spontaneously and grafdually become ET all had associated Dissociated Vertical Deviation (DvD)
Who might we have a planned consecutive ET in surgery?
Planned - Slightly overcorrect as we naturally diverge as we get older = more long-term solution
How might a consecutive ET be unplanned?
Unplanned – at risk of diplopia/will have diplopia
Early: Immediately/ first weeks post-op (diplopia)
Late: Months / years post-op
What is the most common type of post-op Consecutive ET?
Unplanned!
Why might we get early (first day or first few weeks) unplanned post-op consecutive ET?
Early - first day or first few weeks post-op
- Muscle slippage (receded backwards)
- Lost muscle
- Incorrect positioning of muscle (human error)
- Over liberal surgery (human error)
- Inadequate diagnosis (human error, can be caused by the orthoptist giving incorrect figures in PCT or it wasn’t checked that it was simulated or true or if it was laterally incomitance)
Why might we get late (months/years) unplanned post-op consecutive ET?
- Limitation of abduction
- Lack of fusion (become ET)
How can muscle slippage occur and lead to a consecutive ET?
If the sutures only attach the capsule which surround the muscle (tendon) and ligaments. Tendon back.
Tenons capsule goes beyond this point it becomes harder to retrieve it.
Recoils back beyond tenons capsule, extensive surgery, invasive. Untraceable. May have to put the SR and IR transpose it or place it next to the lateral rectus – RARE!
What’s the difference between a lost and slipped muscle?
Lost Muscle -
If unguarded after dissection and disinsertion, the muscle may slip back through its penetration of Tenon’s capsule into the posterior orbit. It may be impossible to retrieve.
Slipped Muscle -
Muscle tendon slips back within the tendon capsule which is still attached to the globe - retrievable.
What are the signs of a muscle slippage?
- Large consecutive deviation immediately post-op
- Limitation of eye movement in direction of action of slipped muscle - less than 10 degrees past midline BUT
Plager & Marshall Parks (1990) describe the possibility of up to 30 deg duction - Proptosis (eyeball bulging out as the muscle may be pushing the eye, very uncommon)
- Widening of palpebral fissure (distance between upper and lower lids) to side of action of slipped muscle >1mm towards the adduction side (affected side in a consecutive ET)
- CT scan / Surgical exploration
How much would we want to overcorrect an Intermittent Distance XT to get a planned post-op Consecutive ET?
Intermittent distance exotropia - aim to overcorrect by up to 14PD to produce long term success
How do we investigate a Consecutive ET?
- History (clues too like surgical scars)
- Test VA as it could damage the eye so very important to do VA
- Cover Test
- Ocular movements – to check for slipped or lost muscles
- Functional / Non-Functional – BSV tests, particularly motor fusion (diplopia or suppression)
- Diplopia / Suppression / Is there a suppression area?
- Size of deviation (N, D, FD, versions, elevation and depression)
