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Clinical Pearls & Morning Reports

Posted by Carla Rothaus, MD

Published December 20, 2023

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What are some of the features of ocular tuberculosis and ocular syphilis?

Uveitis is an important cause of blindness worldwide. Most cases are idiopathic or immune-mediated, but the cause is infectious in 10 to 20% of cases in developed countries and in 30 to 50% in developing countries. Read the NEJM Review Article here.

Clinical Pearls

Q: What is the most important risk factor for microbial keratitis in the United States?

A:Corneal infections, or infectious keratitis, can rapidly affect vision. Contact lens wear is the most important risk factor for microbial keratitis in the United States. There are approximately 45 million contact lens wearers in the United States, and 1 million seek health care for contact lens–related complications annually. Bacteria cause approximately 90% of cases of contact lens–related keratitis in the United States, most commonly Pseudomonas aeruginosa (>40%), Staphylococcus aureus, or streptococci. Corneal trauma is the primary risk factor for microbial keratitis in many agricultural regions of the world. Molds (e.g., aspergillus and fusarium) are major keratitis pathogens in these regions.

Q: How is endophthalmitis defined?

A: Endophthalmitis is a potentially blinding intraocular infection of the vitreous humor, aqueous humor, or both. Nearly all cases are caused by bacteria or fungi. Endophthalmitis results in severe vision loss (less than 20/200) in at least 20% of affected eyes. The infection may be exogenous, developing after eye surgery, intravitreal injections, penetrating trauma, or keratitis, or it may be endogenous. Endogenous infection accounts for 2 to 15% of endophthalmitis cases. Sources of endogenous infection include endocarditis, urinary tract infections, abdominal abscesses (e.g., liver abscess), pneumonia, gastrointestinal procedures (e.g., endoscopy), central venous catheters, and injection-drug use. Patients with current or recently removed central venous catheters are at particular risk for candida endophthalmitis, which may be indolent and initially mistaken for uveitis.

Morning Report Questions

Q: Name the most common infectious cause of posterior uveitis.

A: Ocular toxoplasmosis is the leading infectious cause of posterior uveitis in most studies worldwide and typically causes a chorioretinitis that is self-limited but that heals with scarring. Patients often report decreased vision, but ocular toxoplasmosis may be asymptomatic, especially if the lesions affect the peripheral retina. Antibiotic treatment does not kill toxoplasma cysts. Frequent recurrences of ocular toxoplasmosis are common and may lead to permanent vision loss, especially if the macula is involved. The classic finding in symptomatic ocular toxoplasmosis is a creamy chorioretinal lesion adjacent to a pigmented scar. The diagnosis is made through funduscopic examination and is supported by positive serologic testing.

Q: What are some of the features of ocular tuberculosis and ocular syphilis?

A: Tuberculosis involves the eye in approximately 1.5% of patients with confirmed systemic tuberculosis, and in these patients, the most common eye findings are multifocal choroiditis, a solitary choroidal nodule, anterior granulomatous uveitis, and retinal vasculitis. Serpiginous-like choroiditis is a pattern of choroiditis thought to be highly suggestive of tuberculosis, but it must be distinguished from idiopathic serpiginous choroiditis. Ocular syphilis occurs in approximately 1% of U.S. syphilis cases, usually in secondary or late-stage syphilis or in syphilis of unknown duration. The manifestations are protean, but uveitis is most common, occurring in approximately 65% of cases. Both eyes are affected in half of patients. The diagnosis of ocular syphilis is made in patients with compatible eye findings and positive treponemal serologic testing; a nontreponemal test is usually but not always positive. Treatment is the same as for neurosyphilis, with high-dose intravenous penicillin administered for 10 to 14 days.

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