color perception. Pain resolves as visual loss commences [9]. MRI reveals demyelinating lesions and may be helpful in establishing the diagnosis of multiple sclerosis. The vision loss is progressive and may occur rapidly over several hours or more slowly over days. Treatment with steroids generally leads to improved vision over several weeks [10]. Consultation with neurology as well as ophthalmology is generally warranted, given the likelihood of other conditions, such as multiple sclerosis, as well as other etiologies of acute vision loss.

Central retinal artery occlusion

Central retinal artery occlusion (CRAO) results in a sudden painless loss of vision. The primary cause of CRAO is embolic disease, but there are numerous other conditions that may cause CRAO as well. Immediate ophthalmologic consultation is warranted as vision may be preserved with treatment. Irreversible vision loss generally occurs after 4 hours of ischemia [11]. Visual acuity at presentation is predictive of final visual acuity. However, in a 1980 experimental study of ischemic time after retinal artery occlusion, restoration of blood flow at 100 minutes was associated with preservation of vision [12]. That being said, the medical and surgical treatments for CRAO have marginal benefit overall in preserving vision. Unfortunately, spontaneous resolution of an embolus is quite rare [13].

Retinal detachment

Retinal detachment is characterized by the separation of the retina from the underlying retinal epithelium. The incidence of retinal detachment is roughly one to two cases per ten thousand people [14,15]. Patients complain of new floaters, squiggly lines, or cobwebs that appear abruptly, associated with visual field loss. Examination with an ophthalmoscope is generally insu cient as the detachment may be at the periphery of the retina where the retina is the thinnest. The classic finding of a white billowing retinal separation is helpful if present, but the presence of a new visual field deficit with new ‘‘floaters’’ requires a dilated examination by an ophthalmologist [16].

The above causes of acute visual loss are all covered in more detail in the article by Vortmann and Schneider elsewhere in this issue.

Orbital cellulitis

Cellulitis involving the orbital tissues is usually an extension of an infection involving the sinuses. Patients may present with significant pain, swelling, and even proptosis, with increased risk of permanent ocular damage and vision loss. Potentially fatal complications of orbital cellulitis include meningitis and cavernous sinus thrombosis. CT scan can define the limits of infection and the presence of an abscess. Admission and emergent ophthalmologic consultation are warranted. This is discussed in detail elsewhere in this issue by Mueller and McStay.

In summary, this article has attempted to provide guidelines to the emergency physician regarding when to call for emergency ophthalmology consultation. It is not intended to provide an exhaustive list of every possible problem that may be encountered in the ED requiring the expertise of an ophthalmologist.

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