1. Approach to a patient with diplopia
Dr. R.R.Battu
Narayana Nethralaya

2. What does the faculty of BSV require?
Perfect ( or near perfect ) alignment of the visual axes simultaneously on the object of regard
Perfect ( or near perfect ) retinal correspondence
Perfect central ( or paracentral ) fusional capability.
Perfect ( or near perfect ) alignment of the retinal receptors
Perfect ( or near perfect ) optics to allow only one image to be formed on the retina and the same single image to be formed on the other

3. What is Diplopia ?
It is when more than one image ( two ) of the object of regard are seen simultaneously
This occurs when….(Mechanisms)
More than one image of the object of regard is formed in the retinae of one or both eyes ( monocular diplopia)
The eyes lose their simultaneous alignment with the object of regard in one or more directions ( or distances ) of gaze (incomitance of ocular alignment – binocular diplopia)
The eyes although aligned, send images to the brain which disallow fusion ( aniseikonia )
Local retinocerebral adaptations to misalignments in early life go askew (paradoxical diplopia, loss of suppression)
Rarely, purely cerebral mechanisms

4. Monocular vs Binocular Diplopia
Key question
Is the double vision present even on monocular eye closure?

5. Monocular diplopia
More than one image of the object of regard is formed in the retinae of one or both eyes…..
Irregular astigmatism ( nebular scars, haze, corneal distortion)
Subluxated clear lenses
Poorly fitting contact lenses
Early cataract
Iridodialysis, polycoria, large iridotomies
Macular disorders – edema, CNVM etc

6. Binocular Diplopia
The eyes lose their simultaneous alignment with the object of regard in one or more directions ( or distances ) of gaze (incomitance of ocular alignment – binocular diplopia)
Key clues
Anomalous Head Position
Vision Blurry in one gaze position, better in another
Vestibular signs
Long tract signs
Obviously misaligned eyes, proptosis
Presence of partial ptosis
Nystagmus

7. Questions to be asked Is there a mis alignment?
If so, in which directions ( or distances ) of gaze?
Which are the hypofunctioning ( and hyperfunctioning ) muscles?
Do they have a neurogenic pattern, or a restrictive pattern or a neuromuscular pattern or a myogenic pattern?

8. Identifying muscle/s involved
AHP
Predominant face turn – horizontal recti
Predominant chin elev/dep – vertical recti, pattern strabismus
Predominant tilt – Obliques

9. Diplopia - Key questions Is the diplopia more for distance or near?
Is the diplopia predominantly horizontal or vertical?
In which direction of gaze are the images maximally separated?
To which eye does the “outer” image belong?
Is there a predominant tilt?
In which position of gaze does the tilt increase maximally?

10. Diplopia charting
Diplopia is maximum ( separation of images) in the field of action of the paralysed muscle.
The false image ( the image belonging to the eye with the hypofunctioning muscle ) is always peripherally situated
Higher in upgaze, lower in downgaze, on the right in right gaze and on the left in left gaze

11. Hess Charting Based on the principle of confusion
Allows for identifying the position of one eye, while the other eye fixes in different positions of gaze.
Effectively demonstrates Sherrington’s and Hering’s laws
Allows for more objective follow up also.

12. The cover-uncover and alternate cover tests
Probably the most important objective tests to evaluate muscle palsies
Measurements with a prism bar allow for measurement
Measure in the 9 cardinal gaze positions
Distance and near

13. Versions & Ductions Allow to assess actual rotation limits
Allow assessment of underactions and overactions of synergists

14. Saccadic Velocity
“Floating saccades” are suggestive of a nerve palsy or paresis
Indirectly “oblique saccade” testing can be done.
Normal saccadic velocity with limitation indicates a restricted muscle

15. Forced Duction Testing
Allows to assess forced movement in direction of restriction
Important in Blow out fractures, TED, long standing strabismus with contractures
Important to lift the globe and rotate

16. Force Generation Testing
Allows to identify residual power in a suspected paretic muscle. Usually done to direct management
6th N palsy
Recess – resect or muscle transposition

17. Pointers to primary orbital disease
Restrictive muscle hypofunction
Proptosis
Signs of orbital inflammation
Signs of anterior segment, lid and adnexal hyperemia or inflammation

18. Neurological disease
Look for supranuclear, nuclear and infranuclear patterns
Look for sensory ( visual ) abnormalities
Look for nystagmus
Look for vestibular – auditory symptoms
Look for other cranial nerve involvement
Look for long tract signs

19. CNS and orbital imaging
Done for obvious neurological patterns
Orbital inflammatory disease, proptosis
Occasionally may avoid or delay
Pupil sparing 3rd in a diabetic
6th Nerve in a hypertensive, image if no spontaneous recovery in a few weeks

20. Imaging CT
MRI
Fat suppression
Stir sequences
MRA vs CT angio

21. Ancillary tests Tests for myasthenia Tests of thyroid function
X- ray chest
Bloods

22. Aniseikonia Occurs when image size disparity exceeds 5%
Previously seen in monocular aphakia
May occur following keratorefractive surgery

23. Convergence insufficiency
Classically for near
Could be primary or secondary

24. Others Suppression scotomas
Decompensated squints with Anomalous Retinal Correspondence
Paradoxical diplopia