Ocular misalignment and ophthalmoparesis result in the symptom of binocular diplopia. In the evaluation of diplopia, localization of the ocular motility disorder is the main objective. This requires a systematic approach and knowledge of the ocular motor pathways and actions of the extraocular muscles. This article reviews the components of the ocular motor pathway and presents helpful tools for localization and common sources of error in the assessment of ophthalmoparesis. Neurology Ophthalmoparesis and diplopia. Normal eye movements share the goal of placing an object of visual interest on each fovea simultaneously to allow visualization of a single, stable object. Clear and stable vision is sustained by mechanisms that hold the object on the fovea, such as fixation and the vestibuloocular reflex. Absent or inadequate ocular motility (ophthalmoplegia and ophthalmoparesis) often results in ocular misalignment, causing the visual symptom of binocular diplopia. Binocular diplopia occurs when an object of visual interest falls on the fovea in one eye and on an extrafoveal location in the other eye. Binocular diplopia suggests dysfunction of extraocular muscles, the neuromuscular junction, cranial nerves, cranial nerve nuclei, or internuclear and supranuclear connections. Correct localization of the underlying lesion is the first step to accurate diagnosis and requires a systematic approach and knowledge of the ocular motor pathways and actions of the extraocular muscles.History and examination of diplopia. When obtaining the history and examining the patient, it is important to determine if the diplopia is binocular or monocular. Binocular diplopia resolves with covering either eye and is the result of ocular misalignment. Proper evaluation of binocular diplopia should determine if it is horizontal, vertical, or oblique; worse in a particular direction of gaze; and worse at distance or near. Eye movement examination should include assessment of ocular motility in the nine diagnostic positions of gaze, ocular alignment (measured with the corneal light reflex test, cover test, or Maddox rod 1 ), and comitance of any ocular misalignment. In a comitant lesion, the amount of ocular deviation is the same regardless of gaze direction, while in an incomitant lesion, the amount of deviation varies with changes in gaze direction.
Pearls• Binocular diplopia resolves with monocular covering of either eye, while monocular diplopia resolves with covering the affected eye.• Visual blurring that resolves completely with monocular covering of either eye has the same localizing value as binocular diplopia.• Monocular diplopia is non-neurologic in origin and is not caused by ocular misalignment. It is usually due to ocular pathology such as refractive error or intraocular causes such as cataracts.
2• Worsening diplopia in a particular gaze direction suggests that motility in that direction is impaired.• Esodeviation is a relative medial deviation of the eyes. Exodeviation is a relative lateral deviation of the eyes. Hyperdev...