Basic Principles Of Non Surgical Management Flashcards
What is the aim of non surgical management
- aim is to achieve good well maintained bsv for all distances
- non surgical treatment alone is only successful in deviations less than 20-25 diopters
- if you try to treat patients with larger deviations you may only successfully treat them in short term
- non surgical treatment is also useful when a delay in surgery is deemed appropriate
- to augment the results of surgery
What are convex + lenses used to treat
Rays from nearby objects need to be converged more to form an image on the retina
Long sightedness is corrected using a converging lens
Correct (hypermetropia) long sightedness
- you need the + lenses to refract the light so that it comes to focus sooner
What do convex lenses do in front of the emmetropic eye
- convex lenses in the emmetropic eye
Relax accomodation (converge the light) - you need to do less
- the + lense is doing more refraction for you
What do concave - lenses
- correct myopia
- diverge light
- concave - lenses placed in front of the emmetropic eye stimulate accomodation
- if the light has diverged through the lens you need to accomodation in order to bring the light back into focus
What do base out prisms and base in prisms do
- base out prisms stimulate convergence
- base in prisms stimulate divergence
What are the purposes of orthoptic exercises
- eliminate supression
- elimination of supression gives them diplopia which is the best stimulus for diplopia to fuse
- improve fusion range
Using prism bar, synoptophore , convergence
Improved controlled binocular acuity
- repeated testing
- bar testing
How would you test cba
Patient is requested to read down a chart at the required distance
The examiner observes the ocular alignment of the patient
End point is when the patient becomes manifest - e.g. eso or eco
The patient has reached their max level of va whilst maintaing control
If you see them becoming manifest at 0.3 they would have a cba of 0.4
How is accomodation and convergence affected in eso deviations
- in eso deviations accomodation may be relatively less in order to maintain bsv
- patients may manipulate their accomodation or vergence in order to keep things binocular - that causes blurred vision - or they try and keep things clear and become manifest
If you accomodate you try to converge therefore if you accomodate less then you converge less which should help you to maintain bsv
In eco deviations is accomodation normal
In exo deviations accomodation may be in excess of normal in order to try and remain binocular
What is positive relative convergence
- you trying to get them to converge in excess of accomodation and this is used to control and exo deviation
In an eso deviation what would give them
- convex + lenses
- base out prisms and test their negative relative convergence
Convex lenses reduce their accomodation effort and reduce their convergence
In a eso deviation if they are accomodating that’s also going to give them convergence
Negative relative convergence
- for every diopter of accomodation they initiate you want them to verge less
If you gave them convcave lenses they would need to accomodate more and that would produce even more eso
For an exo deviation what would you give them
- concave lens
- base out prisms
- positive relative convergence
What is positive relative convergence
- vergence is exerted in excess of accomodation
This component is improved in exo deviations
So that can relative vergence can be used to control the strabismus whilst the correct amount of accomodation is exerted to give clear vision
What is negative relative convergence
- vergence is relaxed in relation to the amount of accomodaiton exerted
- improved in eso deviations so that sufficient accomodation can be used for clear vision at all distances without associated convergence
What is the purpose of improving relative vergence
- improve cba
Level of va achieved whist bsv is maintained
To allow the continued use of clear bsv
