orthoptic management of inconstant palsies Flashcards
(38 cards)
what is the difference between a paresis and a paralysis
paresis = still some muscle function left
you wont have a -4 limitation on adduction you may have a -1 or -2
what do you need to know from the investigation
wheather the palsie is a paresis or a paralysis
level of incomitance - i.e. muscle sequelae - has the full muscle sequelae developed or is there just an ov reaction of the contralateral synergist
is there a difference holding the prism in front of one eye vs the other - i.e. is there a difference between the primary and secondary deviation
differential diagnosis - acquired vs congenital , recent vs longstanding
recently acquired patients are much more symptomatic compared to someone who has it for a while
symptoms
diplopia , pain , ptosis, reduced vision , nystagmus, other-
e.g. diplopia due to some form of strabismus or pain from a blowout fracture
what do you need to know about the diplopia
weather it is constant or intermittent
direction - i.e horizontal, vertical , torisonal
the largest separation of images - which positions of gaze
near distance or both fixation distances
can they relieve diplopia closing one eye - which eye do they prefer to close
e..g patients with a 6th nerve palsies are much more likely to say that it is worse for distance than it is for near
diplopia is worse on the affected sides compared to the non affected sides - ask them if they can make the double vision go away
if someone has double vision and they cover one eye and it goes away what does that tell you
- you know if the diplopia is monocular or binocular - I e..g f you cover one eye and they say they can only see 1 - ask pt if they have a preference looking with one eye vs the other
if someone has monocular diplopia e..g in one eye due to di0lopia when you cover the unaffected eye they will have diplopia
with a nerve palsy - its a binocular reason because the muscles of the eyes are not working together
what do you need to know regarding pain
when and which positions of gaze
ie..e in elevation or depression - particular directions of gaze
what do you need to know regarding vision/ visual loss
imformation regrading levels of colour vision , contrast sensitivity, any visual field defects
in some conditions i.e. multiple sclerosis it can effect the optic nerve head and associated optic neuritis - so it affects vision. , colour vision , contrast sensitivity
what do you need to know regarding ptosis
weather it is complete or partial
benefit of ptosis = no diplopia - nothing is done straight away because they are not appreciating diplopia however if they start recovering and the lid starts elevating and they still have ocular misalignment they may start complaining of diplopia and this must be recorded
what do you need to know regarding nystagmus
the type and direction
constant / intermittent
oscilliopsia
in patients who suffer a stroke they may have associated nystagmus - they Can actually suffer a nerve palsy but they can also present with associated nystagmus
what is the recovery rate
recovery rate depends on aetiology - vascular cause recovery rate is generally quick - may be the first 6 months for some it may be just a few weeks or a couple days or months however if you have a space occupying lesion unless that is removed in some way It could actually become worse
what are the aims for orthoptic management
aim - observation - allow time for spontaneous recovery before consider surgery
9- 12 months and ocular motility stable for at least 3 months
during observation period - monitor any improvement/ deteoriation
offer conservative management
make patient comfortable , restore potential bsv , obtain good ocular alignment if no bsv. potential
what are methods of relieving/ minimising diplopia
if a patient presents with diplopia you relieve this by using prisms to join the diplopia image into 1 - if they are not comfortable with prisms you may have to result to occlusion
teach app
prisms
occlusion
what does the type of app adopted depend on
type depends on direction go diplopia
positon of gaze appreciate diplopia
types = head turn , head tilt , chin elevation , chin depression
what are the aims of ahps
move the eyes away from the field of action go parresed muscle and into a positon where the deviation is the least
what would be the typical app in a patient with a left sixth nerve palsy and diplopia to the left
if a patient has a left 6th nerve palsy and they look to the left and they have diplopia to the left so they head turn to the left so their eyes are more right
what are the aims of the use of prisms
restore bsv- use smallest prisms which restore comfortable bsv
move image into suppression area if potential bsv = absent
e.g. if someone has a 15d prism you would not give them 15d because you want them to use the fusional reserves they have left - as you increase the fresnel prism they become harder to see through so you get more lines as you increase the strength of the prism - i.e. if you give then 10 diopter and they can maintain a single image it may be more beneficial as it will have less of an impact on their visual acuity - if they don’t have bsv - i.e. they are suppressing - you may seperate the images further
separate images further if no potential bsv or suppression area
what are the types of prisms used dependent on
types depend on ——-
- direction of diplopia - i.e. if they have an esotropia a base out prism will be given
constant / intermittent diplopia
if they only complain of diplopia in the distance they you will only put diplopia on the distance segment of their glasses
distances apprectiate diplopia
position of gaze that diplopia is appreciated in
duration and stability of deviation
what type of prisms can be given
temporary - fresnel primsms
permeant - incorporate prisms
during the observation period fresnel prisms are given - if they remain stable then you may want to incorporate a prism
disadvantages of prisms = they get discoloured and have to be constanty changed
fit - full lens
distance or reading glasses only
upper segment or bifocal segments
split prisms
what are the disadvantages of fresnel prisms In terms of optical distortion
optical distortion
- horizontal magnification
vertical magnification
curvuture of vertical lines (less so in prisms incorporated into glasses)
asymmetric horizontal magnification
change in vertical magnification with horizontal angle
what are the disadvantages of using fresnel prisms regarding chromatic dispersion
chromatic dispersion - diffraction of light by grooves in Fresnel prisms
cause reduced contrast- effects va , contrast sensitivity fusion and steroacuity
reduction substantial if prism is more than 10 diopters
incorporated into glasses to reduce va to 6/9 - (0.15 logmar)
fresnel prisms reduce va to 6/12 (0.30 logmar)
dynamic visual acuity
the ability to discriminate an object when there is movement between object and individual
dva is increasingly reduced as fresnel prism strength increased
identification of orientation of a moving landolt c viewed at 57cm
what happens to va when you increase prism power
visual acuity reduces with increasing prism power
if you put a 5 diopter fresnel prism up it reduces the va by less than 1 line , 10 diopter reduces it by 1 and a half lines
how is va effected by prisms in mesonic and photopic conditions
progressive condition in va photopic (DAY LIGHT) and mesonic (night) condiitions - participants were dark adapted for 5 minutes
what are the advantages of using fresnel prisms
orientation of prism has no effect on va and contrast sensitivity
lightweight
easily changeable
may relieve ahp
may allow return to work and ability to do daily tasks
how to fit fresnel prisms
decide which eye - the amount of deviation needs correcting - - orientation of prism if both horizontal and vertical deviation present
