Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: Nerve fibre bundle visual field defects are the hallmark of pathology at the optic nerve head or retina. In the present series, six eyes of four patients with large intracranial mass lesions demonstrated such field defects with visual acuity spared in three of the involved eyes. In no cases did visual function in the opposite eye offer a clue to the localization of the lesion.
Output:
Adult