Diagnostic Testing

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Binocular (Fusion) Eye Movements

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Binocular (fusion) eye movements are synchronized eye movements that help maintain a clear and steady single image despite having two eyes, 12 extraocular motility muscles, and six cranial nerves controlling everything.

My residents often consider binocular eye movement-related problems and understanding the systems governing fusion as some of the more challenging problems encountered in ophthalmology and neuro-ophthalmology. The symptoms are often vague and difficult to describe. Furthermore, assessing and describing abnormal binocular eye movements are often subtle or challenging.

While ductions (ocular rotations) and alignment are often better conceptualized, abnormalities in binocular eye movements can be just as impactful to vision as strabismus or gaze palsy.

There are six different binocular eye movements:

  • Fixation

  • Saccades

  • Smooth pursuits

  • Vestibular-ocular reflex

  • Optokinetic system

  • Vergences

While the Basic and Clinical Science Course explains these systems in detail and shows the underlying pathways that govern each system (important for localization of lesions), I typically teach residents to consider these movements based on what the eyes are doing, what the head is doing, what the object of interest is doing, and how fast the movements are. All these movements are supranuclear (that is, the signals that control these movements are initiated before the cranial nerve nuclei are activated), so diseases that cause abnormalities in these eye movements affect cortical or brainstem structures rather than peripheral nerves or muscles.

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Horner Syndrome: Pharmacologic Diagnosis

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Horner syndrome describes the constellation of findings associated with a lesion affecting the oculosympathetic pathway. Clinically, ipsilateral miosis, ptosis, and anhidrosis form the classic triad, with other features potentially being present.

Without getting into too much detail about the sympathetic pathways and differential diagnosis of Horner syndrome (those will be covered in other articles), I will attempt to highlight the 3 pharmaceutical agents used in the diagnosis of Horner syndrome, discuss the tests, and point out the key ideas that often find themselves in tests.

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Diagnostic Criteria For Pseudotumor Cerebri (Idiopathic Intracranial Hypertension)

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Pseudotumor cerebri syndrome (PTC, also referred to as idiopathic intracranial hypertension [IIH]) is classically taught as presenting in young, overweight women of childbearing age, with a history of headaches and findings of bilateral optic nerve swelling, associated with an elevated intracranial pressure.  However, as with every "textbook" definition of a disease, there are atypical cases (children, men, thin people, older people), and so I am often confronted with some interesting diagnostic challenges when I am referred a patient that does not fit the typical picture of PTC who has bilateral optic nerve swelling.

Visual Fields: Introduction

Before we get started with the individual techniques of measuring visual fields, it's important to understand some basic terms and principles.  Entire books have been written about visual fields, so while this and similar articles are geared towards basic review, you may wish to check out some of the resources below to get more details.