management of ic deviations Flashcards
what do you need to know from the investigation
weather it is a paresis or paralysis
the level of incomitance i.e weather muscle sequelae has developed or not
differential diagnosis - is it acquired or congenital
is it recent or longstanding
the symptoms ie.e ptosis , pain , diplopia decrease in vision , nystagmus or other
what do you need to know about diplopia
is it constant or intermittent
what direction i.e. horizontal or vertical or torsional
where is the largest separation of images, i.,e. what positions of gaze , near distance or both fixation distances
are they able to relieve diplopia by closing one eye and which eye do they prefer to close
what do you need to know about the symptoms- regarding pain
do they have pain - when and what positons of gaze
what do you need to know regarding colour vision/ visual loss
do they have reduced colour vision
do they have reduced contrast sensitivity
do they have visual field defects
what do you need to know regarding ptosis
is it complete/partial
what do you need to know regarding nystagmus
type and direction
constant / intermittent
ocscillipsia
what are the aims of orthoptic management
observation - allow time for spontaneous recovery before considering surgery
9-12 months and ocular motility stable for at least 3 months
what do you need to do during the observation period
monitor improvement / deterioration
offer conservative management
make patient comfortable
restore potential bsv
obtain good ocular alignment if no bsv potential
what are methods of relieving / minimising diplopia
teach ahp , prisms , occlusion
what do you need to know about ahp
aim is to move eyes away from the field of parsed muscle
and move eyes to a position where the deviation is the least
type depends on direction of muscle
and position of gaze where they appreciate diplopia
what are the types of ahp
head turn
head tilt
chin elevation head up
chin depression head down
what would the typical ahp in a patient with a left 6th nerve palsy and diplopia to the left be
what are the aims of prism
restore bsv - use smallest prisms which restore comfortable bsv
move image into supression area if potential bsv is absent
separate images further if no potential bsv or suppression area
what do the type of prisms depend on
direction of diplopia
constant/ intermittent diplopia
distances diplopia is appreciated at
positions of gaze where diplopia is appreciated
duration and stability of deviation
what types of prisms are their
temporal - fresnel prisms
permeant - incorporated prisms
what types of fit can you have for prisms
full lenses
distance or reading glasses only
upper segment or bifocal segment
split prisms
what are the disadvantages of prisms
optical distortion
horizontal magnification
vertical magnification
curvture or vertical lines (less so in prisms incooportated into glasses
asymmetric horizontal magnificztion
change in vertical
magnification with horizontal angles
How do fresnel prisms affect chromatic dispersion and dynamic va
cd= fresnel prisms cause diffraction of light by the grooves In the fresnel prisms
reduces contrast
effects visual acuity , contrast sensitivity and steroacuity
and this reduction is substantial if the prism is more than 10 diopters
if incorporated into glasses it reduces va to 6/9
fresnel prisms reduce va to 6/12
dva - ability to discriminate an object when their is movement between the object and individual
DVA is increasingly reduced as fresnel prism strength increased
Identification of orientation of a moving Landolt C viewed at 57cm (Maconachie et al. 2010)
how is va effected with fresnel prisms
va reduces with increasing prism power
progressive reduction in va under photopic (day light) and Mesopic (night) conditions - participants were dark adapted for 5 mins
in photooptic conditions using over 15 diopter prism participants should not be driving
in Mesopic conditions using under 5 diopters participants should not be driving
what are the advantages of 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
what are the indications for prism incoorporation
stable angle of deviation (after observation period)
comfortable in prisms - reasonably concomitant
power of prism relatively small
surgery contraindicated
problems - weight , edge thickness
when would you choose a fresnel prism rather than incorporating the prism into the patients glasses
how successful is the use of prisms
4th nerve palsy
prisms useful is relatively small vertical deviation in pp and fairly concomitant
full correction of angle often required to relieve diplopia
eexpeection - longstanding with extended vertical fusion range
6th nerve palsy
prisms useful is minimal/ small amount of lateral incomintance
typical prism prescribed for horizontal deviations is generally 50% of the total deviation
successful use of prisms more likely if realistic patient expectations , frequent follow up and patient is under 65 years
how successful is the use of prisms
Hatt et al (2014) performed a retrospective study including 34 patients (aged 14-84 years) with diplopia
Aim: determine if successful treatment of diplopia improve HRQOL
Method: two questionnaires pre-prism treatment and at follow up
Diplopia questionnaire: rate severity of diplopia (5-point scale)
Adult strabismus questionnaire: four areas
Self-perception
Reading
Interactions
General function
74% were prescribed Fresnel prism and 26% had prisms incorporated
Conclusion: successful correction of diplopia with prisms improve functional domains but psychosocial domains unchanged
how do you work out the true angle of deviation for a 4th nerve palsie for a longstanding unilateral 4th nerve
prism adaptation
fully correct angle of deviation with prisms for 1-2 weeks
perform pct on return to determine if angle has increased
diagnostic occlusion
occlude the paretic eye (non fixing eye) for 1 day- 2 weeks ft
perform pct before occlusion and on return without allowing binocular vision
what are the options for occlusion and what does it depend on
options for occlusion are
blenderm
bangrter foils
frosted lenses
occlusive contact lenses
type depends on
constant/ intermittent diplopia
position of gaze appreciate diplopia
duration and stability of deviation
which type of occlusion would you choose in a recent onset case with trouble some diplopia that cannot be relieved by prisms
what are the types of fits of occlusion
total occlusion
lower or upper segment occlusion
sector occlusion
what happens after the observation period
you look for outcome
recovery , stability , detoeritaion
management options - conservative management - continue use of small ahp , fresnel prism and occlusion
incorporate prisms , frosted lens , occlusive contact lens
botulinum toxin a
surgery
post botulinum toxin post surgery
ahp, prism and or occlusion for residual symptoms
what factors affect management
general , age , ateiology , general health, occupation
ocular- severity of symptoms, duration since onset , presence and size of ahp, binocular functions , torsion , appearance
what are the orthoptic management options
teach ahp
prisms
occlusion
consider advantages and treatments for each option , factors affecting management , most appreciate treatment option if patient shows recovery , stability , deteoriations
