The Ophthalmology
Survival Guide
The Orbit
The bony socket in which the eye resides provides critical support and protection, an anchor for the extraocular muscles, and continuity with the central nervous system.
Cranial Nerves of the Orbit
Click the images for a magnified view.
Oculomotor Nerve (III)
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Superior rectus muscle
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Medial rectus muscle
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Inferior rectus muscle
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Inferior oblique muscle
Survival Tips!
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The position of the eye in the orbit and its resistance to retropulsion are two key features to assess when evaluating the orbit.
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Symptoms to look for:
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If a lesion occupies space, such as edema, blood, cellular infiltrate, or tumor, it will tend to cause the eye to shift axially outward (e.g. proptosis, exophthalmos) or in another non-axial direction (i.e. ocular dystopia). It may also make the eye more resistant to retropulsion (i.e. the ease with which it may be pushed posteriorly into the orbit).
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Other indicators of orbital disease are limitations of extraocular movement, diplopia, pain, decreased vision, eyelid swelling, eyelid erythema, and conjunctival injection.
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Disease processes that affect the orbital apex or intraconal space tend to be the most sight-threatening.
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Disease processes affecting the mid or anterior orbit within the extraconal space tend to be less immediately sight threatening.
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Globe position and resistance to retropulsion are important to document during comprehensive ophthalmic examination.
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Emergency Care To Note
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An infection involving to orbital soft tissues (i.e. posterior to the orbital septum) is a medical emergency. The inflammatory reaction can produce severe swelling and tissue injury leading to loss of vision, and potential spread in to the brain or cavernous sinus. Prompt diagnosis, including imaging, is critical coupled with empiric administration of broad spectrum antibiotics.
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The key clinical signs that should alert you to an orbital infection are pain, proptosis, limitation of extraocular movement, conjunctival injection, and eyelid swelling. Patients may be febrile as well.
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Remember:
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Preseptal infection can produce dramatic eyelid swelling and erythema, but is not associated with proptosis or loss of extraocular movement. Differentiating between orbital and preseptal infection based on clinical signs is a key survival skill.