scotoma. At presentation vision is usually poor, with 5/36 patients having better than 20/80 in a large case series [128]. Anterior segment inflammation is uncommon in DUSN, although moderate to severe vitritis is almost always present in early stages. The optic disc may be edematous or exhibit mild pallor in early stages. An afferent pupillary defect is almost always present.

The most characteristic features of DUSN involve the retina and RPE. In early-stage disease, multiple, focal, yellow-white lesions in postequatorial outer retina are observed in clusters, and often fade within several days [128, 129]. These evanescent lesions may be accompanied by underlying serous retinal detachment. A subretinal worm can sometimes be observed close to the active retinal lesions. Careful and repeated examination with a fundus contact lens are often required to observe the worm, which appears smooth, tapered on both ends, and often assumes an S-shaped configuration. The worm may be noted to move under direct observation in an apparent aversion to bright light [130].

Late-stage disease is accompanied by reduced visual acuity to less than 20/400, and a large, dense, central scotoma. There is diffuse RPE degeneration which produces a dull reflex reminiscent of a pseudoretinitis pigmentosa; focal areas of depigmentation can develop. There is often notable optic nerve atrophy and retinal arteriolar narrowing [128].

Genetics

There does not appear to be any genetic influence that alters human susceptibility to DUSN.

Diagnosis/Treatment/Complications

The diagnosis of DUSN is made clinically, with observation of a subretinal worm being strongly supportive [130]. Since the disease is localized to the eye, systemic and laboratory evaluations are typically negative. Electroretinogram abnormalities to a moderate or marked degree may be present even when the test is performed early in the disease course [127, 128].

Early recognition and prompt treatment of DUSN may preserve vision. Direct photocoagulation of the subretinal worm in the early phases of disease may be highly effective in halting disease progression and stabilizing

visual acuity [127, 128, 130]. Photocoagulation appears to be the most direct way of killing the worm, and has not been associated with a significant exacerbation in intraocular inflammation. Therapy with corticosteroids has demonstrated transient improvement in inflammation, but its long term success has not been favorable. Antihelminthic therapy did not initially show promise; however successful treatment with oral thiabendazole has been reported in some patients with moderate to severe inflammation [131]. Ivermectin, an antifilarial agent with broad antiparasitic effects, has been used to treat DUSN. Treatment with albendazole may be a bet- ter-tolerated alternative. If suspicion of DUSN is high and the worm cannot be found, medical treatment may be effective in halting disease progression.

Complications from DUSN include severe visual loss from the disease process itself, and rarely CME and choroidal neovascularization.

19.5.5  Congenital Ocular Syphilis

19.5.5.1  Historical Context/Pathophysiology

Syphilis is a chronic multisystemic bacterial infection caused by the thin, spiral-shaped spirochete, Treponema pallidum; it is associated with multiple ocular manifestations that occur in both the acquired and congenital form. Humans are the only known natural host for syphilis, whose history is intimately entwined with human behavior and public health [132]. Syphilis was first described by Leonicenus at the end of the fifteenth century, but it was not until 1905 that Schaudinn and Hoffman of Hamburg identified T. pallidum as the cause of venereal syphilis [133]. Acquired syphilis is most often sexually transmitted, chronic, and systemic. Transplacental transmission from an infected mother to an infant is the cause for congenital syphilis [134]. In 2001, the incidence of congenital syphilis was reported to be 11.1 per 100,000 live births, which reflects the decline in acquired syphilis among women over the past decade [135]. The remainder of this section will focus on syphilis in its congenital form.

Transplacental transmission of T. pallidum may occur throughout pregnancy, with the risk of transmission lower or higher, depending on how long the mother has had syphilis [136]. Maternal serologic screening for syphilis is required during pregnancy throughout the United States, but a significant number of women