Definition
- Strabismus: misaligment of the visual axis
- Phoria: misalignment (deviation) of visual axis when only one eye is viewing
- Sometimes deviated
- Is only present sometimes because image fusion prevents it from happening
- Fusion: merging of the two images of the eye into a single perception
- Fusion can breakdown in fatigue, stress, illness,
- Tropia: misalignment (deviation) of visual axis when both eyes are viewing
- Always deviated
- Named based on the direction of deviation. Exophoria vs exotropia
- Esodeviation: eyes turn in
- Exodeviation: eyes turn out
- Hypodeviation: eyes down
- Hyperdeviation: eyes up
- Cyclodeviation: eye is torted
- Hirschberg test
- A simple clinical screening method used to assess ocular alignment and detect strabismus
- Technique
- A light (such as a penlight) is shone directly into the patient's eyes, typically from a distance of about 50 cm.
- The examiner observes the reflection (corneal light reflex) on the surface of both corneas.
- In normal alignment, the reflex is centrally located and slightly nasal to the pupillary center in both eyes.
- If the reflection is off-center in one or both eyes, it indicates a deviation:
- Temporal reflex = esotropia (eye turned inward)
- Nasal reflex = exotropia (eye turned outward)
- Inferior reflex = hypertropia (eye turned upward)
- Superior reflex = hypotropia (eye turned downward)
Mono-ocular Diplopia
- Causes
- Refractive error
- Astigmatism (imperfections on cornea)
- Poor fitting contact lenses
- Corneal abnormalities
- Keratoconus
- Corneal surface abnormalities
- Tear film disorders: dry eyes
- Refractory surgery
- Corneal transplant
- Lid abnormalities
- Chalazion
- Lid position abnormalities
- Iris abnormalities
- Iridotomy
- Iridectomy
- Miotic pupils
- Lens abnormalities
- Cataract
- Sublux or dislocation
- Intra-ocular lens
- Decentered lens
- Retinal abnormalities
- Epiretinal membrane
- Scar
- Cerebral polyopia
- Description
- When images seen with equal clarity
- Multiple images do not resolve with a pinhole
- Images unchanged when viewed mono-ocularly or bi-ocularly
- Due to
- Occipito/parieto-occipital damage due to infarction, MS, tumour
- Hemifield slide or slip phenomenon
- Due to
- Complete damage of the chiasm → complete bitemporal heminanopia → disruption of ocular fusion (each eye projects one image to each hemisphere) and
- Decompensation of phoria: when both eyes do not look at the same object because each hemisphere has a different image and they don’t talk to each other since the chaism is gone
- Clinical presentation
- Intermittent diplopia
Binocular diplopia
- Horizontal
- Image side by side
- Diseases of the medial or lateral rectus
- Vertical
- Image top and bottom
- Disease of the superior rectus, inferior rectus, superior oblique or inferior oblique
- Image separation is worse in the direction of the of the weak muscle
- The position of greatest image separation: image seen more peripherally corresponds to the eye with poorer motility
Disease of ocular muscle
- Superior oblique tendon sheath syndrome/brown syndrome
- A bit like trigger finger of the eye
- Eye cannot move upwards when adducting but then suddenly releases with a click
- Due to swelling of tendon
- Orbital blow-out fracture
- Incarceration of inferior rectus muscle, inferior oblique
- Diplopia in all direction
- Canine tooth syndrome
- Dog bite → damage trochlear and sup. Oblique together
- Graves disease
- Tight muscle due to mucopolysaccaride lay down
- Frequency involving medial and inferior rectus
- Myasthenia gravis
- All muscle esp medial rectus is weak esp after sustain contraction of that muscle
- The diplopia of myasthenia is intermittent, whereas the diplopia of a compressive lesion is constant or worsening
Common causes of bilateral ophthalmoparesis
Differential Diagnosis | Associated Symptoms and History | Signs | Ancillary Diagnostic Tests |
Pituitary apoplexy | Severe headache, meningismus | Cranial nerve III, IV, V1, V1 or V2 involvement; visual loss may be present | MR imaging, Lumbar puncture |
Myasthenia gravis | Painless, fluctuates with fatigue, dysarthria | Pupil sparing, ptosis, with or without bulbar and generalized weakness | Edrophonium test, electrodiagnostic studies, anti-ACh receptor antibody level |
Botulism | May be associated with GI symptoms: anorexia, nausea, vomiting | Dilated, unreactive pupils, bradycardia, constipation | Electrodiagnostic studies, serum bioassay |
Wernicke's encephalopathy | History of alcohol abuse | Nystagmus, ataxia, confusional state, stigmata of long-term alcohol abuse | Improvement with thiamine |
Guillain-Barré syndrome (Miller Fisher variant) | Preceding GI or upper respiratory illness | Areflexia, ataxia, extremity weakness | Lumbar puncture, electrodiagnostic studies |
Brainstem stroke | History of cardiac arrhythmia, vascular disease | Bilateral long tract signs, skew deviation | Magnetic resonance imaging |
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