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