fluid can also be present, possibly occurring secondary to retinal pigment epithelial destruction [156, 157]. A number of other conditions associated with leukemia can also produce a swollen disc. These are: (1) leukemic infiltration of the central nervous system leading to increased intracranial pressure and papilledema; (2) prolonged use of corticosteroids in conjunction with pseudotumor cerebri;

(3) tumor infiltrates of the orbit or optic nerve producing an ischemic papillitis; and (4) perivascular infiltration leading to venous engorgement and localized swelling [158].

5.8.4  Treatment

Prompt aggressive treatment of early nerve head infiltration is indicated. Irreversible vision loss occurs as the disease progresses. Rosenthal and associates [155] reported treating this condition with 2,000 rads of external beam irradiation over a 1- to 2-week period. The clinical pathology resolved, and the visual acuity returned to normal within 2 to several weeks. In one case, the acuity improved from count fingers to 20/20, and the initially present afferent papillary defect resolved. In some cases, a combination of chemotherapy and radiation may need to be employed.

5.8.4.1  Other Elevated Disc Anomalies

5.9.2  Pathophysiology

Histopathologically, disc drusen are composed of concentric laminations with no cellular structure or capsule. They frequently become calcified. Drusen that may be unrecognized clinically are often found in tissue section as an incidental finding.

5.9.3  Natural History and Prognosis

Optic nerve drusen are rarely seen in early childhood. Some cases may be present at birth and become clinically apparent later as they enlarge and encroach on the disc surface. In doubtful cases, examination of the disc of family members is warranted. Approximately, 75% of ophthalmoscopically visible drusen are bilateral. No relationship to refractive error has been shown. For the most part, only Caucasian children are affected; disc drusen are rarely seen in Afro or Asian children. They may persist for years with little change, and if situated superficially, they are less likely to cause significant symptoms. However, if they lie deeply in the sclerochoroidal canal, they may produce a pressure atrophy of the contiguous nerve fibers with resultant changes in the visual fields [161]. Central visual acuity is usually unaffected.

5.9.4  Diagnosis and Diagnostic Aids

Several lesions that may cause an elevation of the optic nerve head may be misdiagnosed and lead to unnecessary procedures and even surgical intervention.

5.9  Drusen

5.9.1  Introduction

Drusen of the optic nerve head are irregularly raised areas, which often blur the disc margin in an otherwise healthy asymptomatic child. Not present at birth, drusen typically enlarge with time and emerge on the surface ofthediscduringtheearlyteenageyears.Approximately, 75% are bilateral. Optic disc drusen can also be associated with acquired diseases of the optic nerve and heredodegenerative disorders [159, 160].

The surface of the disc frequently assumes an irregular, nodular, mulberry-like appearance. The physiological cup may be absent, but a venous pulse is usually seen. The vessels are unobscured and course from the central apex of the disc. Drusen normally do not cause venous and capillary dilatation or exudates. Disc hemorrhages and peripapilary subretinal neovascularization occur in a small percentage of cases [162]. However, there may be an abnormally large number of tortuous, anomalously branching vessels. These vessels may be of some importance in pathogenesis [163]. Aberrant axoplasmic transport through optic nerve axons has also been implicated [164]. The disc does not show pallor but may have an irregular margin and can be transilluminated. Elevation is confined in the disc and is often more pronounced­ nasally than temporally (Fig. 5.21). Many drusen exhibit autofluorescence (90%) [165]. Sometimes,­ they can be differentiated from papilledema by fluorescein angiography.