management of concomitant exotropia Flashcards
what are the 4 main principles of management for someone with a concomitant exotropia
- Correctly diagnose/classify type of exot
- Best possible VA in each eye
- Restoration of comfortable binocular vision at all distances
- In the absence of potential BV - Best possible cosmesis
what are the 4 steps in the first stage of management
- Diagnosis of type XT
- Refraction, fundus & media examination
- Correction of ametropia
- Amblyopia therapy if under 7 years of age
what do you need to know about a intermittent distance exotropia px
- whether it is a true distance exotropia
- with their near angle where they may have an exophoria can be simulated either by accommodation or fusion i.e. by excessive amounts of accommodation (high AC/A ratio) or their fusional ability
how will you test if a patient has a simulated distance exotropia induced by accommodation
- is to prevent the px to simulate the exophoria at near by putting +3.00D lenses in front of their eyes for near and do a cover test at near using the reduced snellen chart as well as a prism cover test at near
- if with the +3.00D lenses they now have a manifest exotropia at near too and the measurement has significantly simulated due to accommodation
- but if with the +3.00D lenses, they’re still an exophoria at near i.e. similar measurement, then it is not simulated due to accommodation
- however before ruling a simulated distance exotropia out, you need to check that the patient is not simulating their exophoria at near by fusion instead
how will you test if a patient has a simulated distance exotropia induced by fusion/fusional reserves
- you need to prevent the px from using their eyes together as a pair by putting a patch in front of any eye for 45 minute
- then only do a prism cover test
- compare the results of this prism cover test to the one you did before you patched the patient’s eye
- if the patient has 6 pd base in of exophoria right and left and then a 20 pd base in exotropia = simulated distance exotropia by fusion
what are the 5 management options for someone with a concomitant exotropia
- Optical
- Orthoptic Exercises
- Surgery
- Botulinum Toxin
- Observation
in which type of exotropia is orthoptic exercises more successful in and what type of exercise will you give them and why
- near exotropia (have reduced convergence)
- give stereogram exercises - to increase their positive relative convergence
- this is so that they don’t decompensate to an exotropia at near
in which type of exotropia will you want to just monitor/observe as theres no need to do surgery and why
- intermittent exotropia with a small around 15 pd exot at distance
- this is because these patients are usually young and the degree of exotropia will change in most visits so it is not stable enough for surgery
when do near exotropias tend to present and why and how will you treat them
- usually later in life
- as a result of not being able to read properly and will suffer from headaches, asthenopic symptoms
- you can control these patients with prisms
list the 5 options for optical management of a px with a concomitant exotropia
- Full prescription of myopic errors
- Over-minus in some cases
- Under-correct small hyperopic errors compatible with good VA
- Full correction of large hyperopic errors?
- Base in prisms
what is the reason for orthoptic exercises in treating a concomitant exotropia
To improve near point of convergence and positive relative vergence
which 2 types of exot will orthoptic exercises be most useful in
- in small near exos
and - decompensating deviations (into an exotropia from an exophoria)
name 2 types of orthoptic exercises used to improve near point of convergence and positive relative convergence
- dot card used at near or distance fixation depending on which control of angle you want to get better
- stereograms
what is the purpose for doing orthoptic exercises on someone with a near exotropia
- because they’re decompensating from an exophoria and therefore we want to strengthen that little control they got initially so that they control to a exophoria
- give all tests at near fixation to control near convergence
what are the 2 choices of muscles that surgery be done on and what type of surgery will be done on them for a exotropia and what does the amount of surgery depend on
- To weaken the lateral rectus - Recession
- To strengthen the medial rectus - Resection
- amount or surgery depends on the angle
how do you weaken a muscle during surgery
by moving the insertion back
how do you strengthen a muscle during surgery
by moving the insertion of the muscle forward e.g. medial rectus and also shortening the muscle
what do you need to do for any muscle to avoid a patient turning into a consecutive exotropia/esotropia
you need the exact measurements as every mm of muscle moved corrects a certain amount/degree of exotropia they got, therefore if its slightly off it can result in a consecutive esotropia
for surgery, it is usually operated on 2 muscles, list the 3 possible routes a surgeon can go down when doing surgery for a exotropia
- Bilateral recession of lateral recti
- Rescession of LR and resection of MR on same eye
- Bilateral resection of medial recti (Rarely)
which type of muscle surgery is often disappointing and therefore what is ideal for a successful outcome
- 1 muscle surgery
- ideally need 2 muscle surgery
in which type of exceptional circumstance is 1 muscle surgery maybe used in
a secondary exotropia
what is the general rule for surgery if the angle is larger at distance and less at near
Bi-lateral rectus recessions
what is the general rule for surgery if the angle is larger at near and less at distance
Bi-medial rectus resections
what is the general rule for surgery if the angle is the same for distance and near
LR recession and MR resection
just on one eye
what must be checked before doing surgery on a px with an intermittent distance exotropia and why
- an accommodation and fusion test
- because if you just assumed the px had a true distance exotropia and didn’t do any tests, if you did a bilateral rectus recessions, then post surgery the patient would still have large phoria which may still break down into an exotropia at near
under what 3 conditions is surgery only undertaken
- If an intermittent squint is decompensating
- If there are symptoms:
e. g. dipl - If cosmesis is very poor:
from a secondary/sensory exotropia e.g. if they got very poor vision in one eye and a large angled exotropia which looks cosmetically poor, then you want to reduce the angle down, for a secondary exotropia the only management is to improve the cosmesis as the patient won’t have any binocularity by putting the eyes into the straight ahead position, as the patient will always have poor vision in that eye so can’t use both together
what is the 3 classifications which management depends on
- Primary: squint is the primary defect
- Secondary: to loss/impairment of vision usually constant unilateral
- Consecutive: previously convergent
what is the 3 things that needs to be done when treating someone with a primary exo
- Treat amblyopia under 7 years of age
- Assess potential for BV (NB history) using:
Prisms
Synoptophore
Botulinum toxin - Risk of post-operative diplopia should be assessed using:
Prisms/toxin
how will you treat amblyopia of somebody with a constant and unilateral exo and under the age of 7
- start patching treatment and if they have glasses then you want to give them the full adaptation of their glasses
- review them a few months after that
- if they still have reduced vision in that eye, then you want to start patching from that visit onwards
- if they got perfect vision after giving them glasses, then you don’t need to do anything like the above i.e. patching
why and how do you carry out a post op diplopia test
- you align the eyes by one of the methods
- once the eyes are in the straight ahead position, you want to see if they have any potential for any binocularity or not
- look at their fusion to see if they have any stereopsis
- if there is no potential for BV, then you want to see if they’re likely to get any double vision
- use a prism bar as the eyes will be corrected with prisms or a synoptophore
- increase the prism bar to see if they report any double vision at any particular level of the prism bar
- if they were over corrected post operatively e.g. if they measure 20 pd base in and you put up 25 pd base in i.e. over correcting them by 5 pd base i, you want to see if they’re getting any double vision or not
- if they measure 20 pd base in and you put up 50 pd base in and they can still obtain single vision, then that means they have a very low risk of post op diplopia and can proceed for any muscle surgery
under what 2 circumstances can you carry out surgery for a constant exo
if:
No significant A/V pattern
No significant near-distance disparity (so must be similar)
how is surgery for a constant exo carried out
- Surgery to non-fixing eye
- Unilateral Surgery LR recession (weakening) MR resection (strengthening)
- Adjustable sutures
on which age group with a constant exotropia is it good to put adjustable sutures on and why
- on children who are old enough, over 14/15 years old
- tie one suture loosely e.g. to the lateral rectus muscle, and then measure their deviation at distance fixation
- so if you still feel the px is still slightly exo, you can adjust that measurement through surgery to fine tune
- also with exotropia patients, surgeons will leave them post operatively slightly convergent depending on what type of diagnosis they have e.g. with secondary exotropia who don’t have binocular potential so their eyes tend to drift out, so best to leave them slightly over corrected to delay the exotropia over time
what is the prognosis of a cosmetic surgery for a constant exotropia or secondary/sensory exotropia and therefore what is an alternate treatment option
- No guarantee about long-term results:
after any surgical correction of exotropia because or poor/no vision in that eye with the exotropia, it will drift out after a few years - XT may recur – especially if VA is poor:
as theres no demonstrable BV - further possible treatment is with botulinum toxin injected into the lateral rectus, to reduce the exotropia
what does the management of an intermittent exotropia depend on
the type
what is the most common childhood form of exotropia and what is the most common form in adults
- childhood form is distance XT - rarely symptomatic
- in adults, near exo more common - frequently symptomatic
what is usually mild if present in an intermittent exotropia
amblyopia
how will you refract and correct any significant ametropia on a myopic and hyperopic px with intermittent exotropia
- Myopia: for weak myopes, should over minus them as they can control that intermittent exotropia into a exophoria, and then reduce the over minussing technique overtime, but don’t reduce the distance vision significantly, only give over minus if can maintain good visual acuity
- Hyperopia: if they’re highly hypermetropic, you may occasionally need to reduce that prescription down as you don’t want to increase the initial exotropia
what treatment is there no rush for with an intermittent distance exotropic px and why
Surgery
as risk loss of BSV and developing amblyopia with conversion to a consecutive esotropia post operatively
instead of rushing to do surgery for a intermittent distance exotropic patient due to the risk of consecutive esotropia, amblyopia or loss of BSV what should be done instead
- Observe to ensure control not deteriorating enquire frequency of XT observed at home
- you also want to observe their near control whether they’re exophoric, so want to make sure that the level of degree of binocular potential that they do have at near fixation remains stable if their near angle exophoria is decompensating and down to exotropia for near = then consider surgery to rectify
- Possible temporising treatment with over-minus lenses - ? tolerance
when is surgery indicated for someone with a intermittent distance exotropia
if control at near is poor or losing BSV at near fixation or cosmesis significantly poor (child teased)
what type of surgery is carried out on someone with a true distance exotropia
Bilateral LR recessions
what type of surgery is carried out on someone with a simulated distance exotropia
unilateral MR recession, LR resection
what are the 5 possible management options for someone with a intermittent near exotropia
- Correct ametropia appropriately
- May benefit from convergence exercises
- Prisms (fresnel for elderly)
- Botulinum toxin
- Surgery
how does convergence exercises benefit patients with a intermittent near exotropia
for the patients who are able to control to an exophoria but do break down to exotropia immediately the exercises will strengthen their initial control by improving their fusional reserves
what does botulinum toxin as a management for intermittent near exotropia depend on and what must you inform the patient of
- on what their distance angle is like as well
e. g. a small exophoria at distance and decompensating exophoria at near into a 40 pd exotropia = can be given the injection - but do inform the patient that the distance angle that is very small to begin with could increase post botox injection
which surgery is suggested for a intermittent near exotropia in theory and what risks does this cause
what is a better option of surgery instead
- in theory resect both MR
- poor results as can cause esotropia in distance and diplopia on lateral gaze
- Unilateral MR resection, small LR recession (adjustable) better option px needs to be aware of risks
what does the treatment of a non-specific exotropia depend on
the symptoms
list the 4 possible treatment/management options for a px with a non-specific exotropia
- convergence exercises
- prisms (fresnel)
- botulinum toxin
- surgery
when will you suggest convergence exercises to someone with a non-specific exotropia and which types
- if the patient is mostly asymptomatic, to improve their fusion
- with either pen convergence exercises or stereogram
when will you suggest prisms as management for someone with a non-specific exotropia
if the patient breaks down often, give them a fresnel prism
when and what type of surgery will you manage someone with a non-specific exotropia
- if a patient very readily breaks down into an exotropia at distant or near, the surgery you do depends on where the angle of deviation is greatest
- unilateral MR resection, LR recession
what is the management for someone with a consecutive exotropia who has had a muscle slippage and why is this option chosen first
- botulinum toxin
- to initially determine the need and type for further surgery
when is muscle slippage seen in someone with a consecutive exotropia
- seen in limitations e.g. eye doesn’t move as much as it should do
- so need to reattach the slipped muscle after finding out from giving botox
what are the 2 management options for someone with a consecutive exotropia and has not had muscle slippage and what is the further management is this fails
- prisms may be used to gain BSV
or - XT may be reduced by reduction of hyperopic spectacle correction
- if fails then need botox and further surgery
what 3 things must you do to treat someone with a secondary exotropia
- Diagnose and treat underlying condition (investigate why they got this exotropia)
- Treat amblyopia if under 7 years
- Treatment for cosmetic defect:
Squint surgery (as for constant exo)
Botulinum toxin
Shell contact lens (if had penetrating eye injury or cloudy cornea, use coloured lens)
what type of surgery is carried out for someone with a secondary exotropia
Adjustable suture Sx : RLR recession, RMR resection
