Involvement of the optic nerve, either because of inflammation or increased intracranial pressure, is a rare manifestation of Lyme disease. Of the 4 children reported here with optic nerve abnormalities, 2 had decreased vision months after disease onset attributable to optic neuritis, and 1 had headache and diplopia early in the infection because of increased intracranial pressure associated with Lyme meningitis. In these 3 children, optic nerve involvement responded well to intravenous ceftriaxone therapy. The fourth child had headache and visual loss attributable to increased intracranial pressure and perhaps also to optic neuritis. Despite treatment with ceftriaxone and steroids, he had persistent increased intracranial pressure leading to permanent bilateral blindness. Clinicians should be aware that neuro-ophthalmologic involvement of Lyme disease may have significant consequences. If increased intracranial pressure persists despite antibiotic therapy, measures must be taken quickly to reduce the pressure.