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Preoccupied with bacteria, viruses, and fungi, we are apt to forget that certain plants may also pose an occasional threat to our ocular well-being.
One threat, called to our attention by an article published elsewhere in this issue, is the common cockle bur or burdock, whose tiny shafts lock themselves into the tarsal conjunctiva and cause chronic abrasions of the cornea. These motes are particularly noxious, because their protruding points are scarcely visible to the examiner and because the patients are apt to be young children who resist prolonged manipulation of their lids.
The cockle bur presents a double menace. The shafts of the outer layers consist of flexible hairs, each equipped with a single hooklet that enmeshes itself in one's clothes or in animals' fur. The shafts of the inner core, on the other hand, are rigid needles equipped with retroflexed spikes seemingly designed to penetrate tissue. The portion
C. D. Botanical Hazards. Arch Ophthalmol. 1966;75(1):1. doi:10.1001/archopht.1966.00970050003001