Orthoptic management of incomitant deviations Flashcards
What do you need to know about diplopia?
Constant/ intermittent
Direction
Largest separation of images
Is diplopia relieved after closing one eye
What are the directions of diplopia
Horizontal
Vertical
Torsional
Where can images separate
Which position of gaze
N, D or both
What to consider if one eye is closed to relieve diplopia
Which eye prefers to close
Pain
When and which positions of gaze
Reduced vision/ visual loss
colour vision
contrast sensitivity
visual field defect
Ptosis
complete or partial
Nystagmus
type and direction
constant/ intermittent
oscillopsia
Aims of orthoptic management
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/ deterioration
Offer conservative management
Make patient comfortable
Restore potential BSV
Obtain good ocular alignment if no BSV potential
Methods of relieving diplopia
teach AHP
prisms
occlusion
Adopting AHP -type depends on
Direction of diplopia
Position(s) of gaze appreciate diplopia
Aim of AHP
moving eyes away from field of action of paresed muscle and into a position where the deviation is least
Type of AHP
Head turn
Head tilt
Chin elevation (Head up)
Chin depression (Head down)
What would be the typical AHP in a patient with a left 6th nerve palsy and diplopia to the left?
Left
Aim of using prisms
Restore BSV
Use smallest prisms which restore comfortable BSV
Move image into suppression area if potential BSV absent
Separate images further if no potential BSV or suppression area
Type of prism depends on
Direction of diplopia
Constant/ intermittent diplopia
Distance(s) appreciate diplopia
Position(s) of gaze appreciate diplopia
Duration and stability of deviation
Prism options
Temporary – Fresnel prisms
Permanent – incorporate prisms
Fit of prisms
Full lens
Distance or reading glasses only
Upper segment or bifocal segment
Split prisms
Fresnel prism disadvantages
- Optical Distortion
Horizontal magnification
Vertical magnification
Curvature of vertical lines (less so in prisms incorporated into glasses)
Asymmetric horizontal magnification
Change in vertical magnification with horizontal angle
-Chromatic dispersion
Diffraction of light by grooves in Fresnel prism
Cause reduced contrast
Effect VA, contrast sensitivity, fusion and stereoacuity
Reduction substantial if prism >10∆
10∆ prism (Kulnig, 1987)
Incorporated into glasses: reduce VA to 6/9 (~0.15 logMAR)
Fresnel prisms: reduce VA to 6/12 (0.30 logMAR)
-Dynamic visual acuity (DVA)
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 (Maconachie et al. 2010)
With increasing prism power
visual acuity reduces
Fresnel prisms advantages
Orientation of prism has no effect on VA and contrast sensitivity (Veronneau-Troutman, 1978)
Lightweight
Easily changeable
May relieve AHP
May allow return to work & ability to do daily tasks
What to consider when fitting a prism
Which eye?
The amount of deviation needs correcting
Orientation of prism if both horizontal and vertical deviation present
Fitting prisms
Fit
Draw outline slightly smaller than edge of lens using non-permanent marker pen
Place under water
Apply prism to back surface of lens
If very high curvature (high myopic correction) apply to front surface
Remove air bubbles by wiping/pressing in apex to base direction
Incorporation of prisms
Indication
Stable angle of deviation (after observation period)
Comfortable in prisms
Reasonably concomitant
Power of prism relatively small (<8 PD either eye)
Surgery contraindicated
Problems
Weight
Edge thickness
When would you choose a Fresnel prism rather than incorporating the prism into the patient’s glasses?
when prism dioptre is small and a temporary problem
Success of prisms in fourth nerve palsy
Prisms useful if relatively small vertical deviation in P.P. and fairly concomitant
Full correction of angle often required to relieve diplopia
Exception: longstanding with extended vertical fusion range
Success of prisms in sixth nerve palsy
Prisms useful if minimal/small amount of lateral incomitance
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 >65 years
(Gunton and Brown, 2012)
How successful is use of prisms - study
Diplopia impacts on patients’ health related quality of life (HRQOL)
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
How successful is the use of prisms? study
Results: 23 of 34 were successfully treated with prisms
74% were prescribed Fresnel prism and 26% had prisms incorporated
Significant improvement in
Diplopia questionnaire
Adult strabismus 20 questionnaire
Improvement in general and reading function
Unchanged for self-perception and interactions
Conclusion: successful correction of diplopia with prisms improve functional domains but psychosocial domains unchanged
Aim of prism adaptation/ diagnostic occlusion 4th nerve palsy
determine the true angle of deviation
Advocated for longstanding unilateral SO palsy
Method of prism adaptation
Fully correct angle of deviation with prisms for 1-2 weeks
Perform PCT on return to determine if angle has increased
Method of 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
Type of occlusion depends on
Constant/ intermittent diplopia
Position(s) of gaze appreciate diplopia
Duration and stability of deviation
Options of occlusion
Blenderm
Bangerter foils
Frosted lens
Occlusive contact lens
Which type of occlusion would you choose in a recent onset case with troublesome diplopia that cannot be relieved by prisms?
Fitting of occlusion
Total occlusion
Lower or upper segment occlusion
Sector occlusion
After observation - outcome management, post BT and surgery
Outcome- Recovery, stability,, deterioration
Management- Conservative management, continue use of small AHP, Fresnel prism and occlusion, incorporate prism, frosted lens, occlusive contact lens, BT, surgery
Post BT/ surgery- AHP, prism and/or occlusion for residual symptoms
Factors affecting management
-General
Age
Aetiology
General Health
Occupation
-Ocular
Severity of symptoms
Duration since onset
Presence and size of AHP
Binocular functions
Torsion
Appearance
Orthoptic management options for incomitant deviations
Teach AHP, prisms, occlusion
Consider
-Advantages/disadvantages for each treatment option
-Factors affecting management
-Most appropriate treatment option if patient shows:
Recovery, stability or deteriorations
