A number of other conditions may produce non-AMD macular degenerative changes with central vision loss caused by CNV, atrophy, or scarring. CNV management, while historically focused on laser therapies or PDT, has evolved to incorporate intravitreal anti-VEGF agents using treatment protocols similar to those used for neovascular AMD, with similar visual acuity gains.
Ocular Histoplasmosis Syndrome
Histoplasma capsulatum fungus is endemic to the Mississippi and Ohio River valleys. Humans become infected by inhaling the yeast form of this fungus, which then disseminates throughout the bloodstream. Although the systemic infection eventually subsides, the individual may be left with chorioretinal scars that produce visual symptoms years later.
Ocular histoplasmosis syndrome (OHS) is also referred to as presumed ocular histoplasmosis syndrome (POHS) because the causality has never been definitively confirmed. OHS is most prevalent among the population with the greatest percentage of positive skin reactors; over 90% of patients with the characteristic OHS fundus appearance react positively to histoplasmin skin testing. In 1 community with endemic histoplasmosis (where 60% of the total population reacted positively to histoplasmin skin testing), the characteristic peripheral lesions of OHS occurred in 2.6% of the total population surveyed and in 4.4% of the positive skin test responders. Only 1 individual with peripheral lesions showed disciform macular disease. The organism has been identified histologically in the choroid of 5 patients with OHS. Nevertheless, other etiologies besides H capsulatum may produce a similar phenotype (see also the section “Multifocal choroiditis” in Chapter 11).
Clinically, OHS presents with small, atrophic, “punched-out” chorioretinal scars in the midperiphery and posterior pole (“histo spots”), linear peripheral atrophic tracks, and juxtapapillary chorioretinal scarring with or without CNV in the macula (Fig 4-15). Lesions are bilateral in more than 60% of infected individuals, and characteristically, there is an absence of vitreous inflammation. Most patients with OHS are asymptomatic until the development of CNV, which may cause vision loss, metamorphopsia, and paracentral scotomas. FA and OCT findings are useful for guiding diagnosis and monitoring response to therapy. Other diseases with features similar to OHS include multifocal choroiditis and panuveitis; see also BCSC Section 9, Uveitis and Ocular Inflammation.
Management of ocular histoplasmosis syndrome
There is no specific medical management necessary for OHS. When CNV develops, anti-VEGF therapy is helpful.
Nielsen JS, Fick TA, Saggau DD, Barnes CH. Intravitreal anti–vascular endothelial growth factor therapy for choroidal neovascularization secondary to ocular histoplasmosis syndrome. Retina. 2012;32(3):468–472.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.