orthoptic management of inconstant palsies

Question 1

what is the difference between a paresis and a paralysis

Answer 1

paresis = still some muscle function left

you wont have a -4 limitation on adduction you may have a -1 or -2

Question 2

what do you need to know from the investigation

Answer 2

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

Question 3

what do you need to know about the diplopia

Answer 3

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

Question 4

if someone has double vision and they cover one eye and it goes away what does that tell you

Answer 4

• 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

Question 5

what do you need to know regarding pain

Answer 5

when and which positions of gaze

ie..e in elevation or depression - particular directions of gaze

Question 6

what do you need to know regarding vision/ visual loss

Answer 6

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

Question 7

what do you need to know regarding ptosis

Answer 7

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

Question 8

what do you need to know regarding nystagmus

Answer 8

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

Question 9

what is the recovery rate

Answer 9

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

Question 10

what are the aims for orthoptic management

Answer 10

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

Question 11

what are methods of relieving/ minimising diplopia

Answer 11

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

Question 12

what does the type of app adopted depend on

Answer 12

type depends on direction go diplopia

positon of gaze appreciate diplopia

types = head turn , head tilt , chin elevation , chin depression

Question 13

what are the aims of ahps

Answer 13

move the eyes away from the field of action go parresed muscle and into a positon where the deviation is the least

Question 14

what would be the typical app in a patient with a left sixth nerve palsy and diplopia to the left

Answer 14

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

Question 15

what are the aims of the use of prisms

Answer 15

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

Question 16

what are the types of prisms used dependent on

Answer 16

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

Question 17

what type of prisms can be given

Answer 17

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

Question 18

what are the disadvantages of fresnel prisms In terms of optical distortion

Answer 18

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

Question 19

what are the disadvantages of using fresnel prisms regarding chromatic dispersion

Answer 19

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)

Question 20

dynamic visual acuity

Answer 20

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

Question 21

what happens to va when you increase prism power

Answer 21

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

Question 22

how is va effected by prisms in mesonic and photopic conditions

Answer 22

progressive condition in va photopic (DAY LIGHT) and mesonic (night) condiitions - participants were dark adapted for 5 minutes

Question 23

what are the advantages of using fresnel prisms

Answer 23

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

Question 24

how to fit fresnel prisms

Answer 24

decide which eye - the amount of deviation needs correcting - - orientation of prism if both horizontal and vertical deviation present

Question 25

in what type of patient is prisms indicated in

Answer 25

indication for prisms -stable angle of deviation (after observation period)

comfortable for prisms - reasonably concomitant

power of prism relatively small e.g. more than 8 dioptrers either eye

surgery contraindicated

Question 26

what are the problems of prism incooporation

Answer 26

weight

edge thickness

Question 27

when would you choose a fresnel prism rather than incorporating the prism into the patients glasses

Answer 27

fresnel prism = temporary solution

prism = used when patients are more stable

in a 4th nerve palsy you usually have a vertical deviation and in the affected eye you would usually have a hypertroppia

patients with a 4th nerve palsy usually have an extended vertical fusion range - e.g. even though they measure 15 diopter you may need to only give them a 8 diopter because they have an extended vertical fusion range

Question 28

how successful is the use of prisms

Answer 28

4th nerve palsy - prisms useful if relatively small vertical deviation in p.p and fairly concomitant

full correction of angle is required to relieve diplopia

exception : longstanding with extended vertical fusion range

6th nerve palsy - prisms are useful if minimal/ small amount of lateral incomitance

typical prisms prescribed for horizontal deviations is generally 50% of the total deviation

successful use of prisms is more likely If realistic patient expectations , frequent follow- up , and patient is over 65 yrs

Question 29

how successful is the use of prisms -

Answer 29

successful correction of diplopia with prisms improve functional domains but psychosocial domains unchanged

Question 30

what is the aim of the prism adaptation test

Answer 30

aim is to determine the true angle of deviation

advocated for longstanding unilateral superior oblique palsies

Question 31

what is the method for performing the prism adaptation test

Answer 31

methods - fully correct the angle of deviation with prism for 1-2 weeks

perform pct on return to determine if angle has increased

Question 32

what is the method for diagnostic occluison

Answer 32

occlude the paretic eye (non fixing eye) for 1 day - 2 weeks ft

perform pct before occlusion and on return without allowing binocular vision

Question 33

what occlusion options do you have

Answer 33

blendaderm

bangerter foils

frosted lenses

occlusive contact lenses

Question 34

what does the type of occlusion depend on

Answer 34

constant/ intermittent diplopia

positions of gaze appreciate diplopia

duration and stability of deviation

Question 35

which type of occlusion would you choose in a recent onset case of troublesome diplopia that cannot be relieved by prisms

Answer 35

you give a patient occulsion if you cannot relieve the diplopia with prisms - is the diplopia there all the time or all in certain positions of gaze

blendaderm - can place on a place of Plano glasses if they don’t wear glasses already

Question 36

what are the different types of ways occlusion can be fitted

Answer 36

total occlusion

lower or upper segment occlusion

sector occlusion- most commonly used in 6th nerve palsies

Question 37

what would be done after the observation period

Answer 37

outcomes = recovery, stability , deterioration

management options - conservative management - continue use of small app , fresnel prism and occlusion

incorporate prisms, frosted lenses , occlusive contact lens

botulinum toxin a

surgery

post botulinum toxin / post surgery

app, prisms and / or occlusion or residual symptoms

Question 38

what factors affect management

Answer 38

general - age , aetiology , general health, occupation

ocular - severity of symptoms , duration since

onset , presence and size of app , binocular functions , torsion , appearance

]