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

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

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

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

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

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

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?

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

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?

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

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.

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

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

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

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

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

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

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

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

Imaging CT MRI Fat suppression Stir sequences MRA vs CT angio

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

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

Convergence insufficiency Classically for near Could be primary or secondary

Others Suppression scotomas Decompensated squints with Anomalous Retinal Correspondence Paradoxical diplopia