2020–2021 BCSC Basic and Clinical Science Course™
8 External Disease and Cornea
Chapter 14: Clinical Aspects of Toxic and Traumatic Injuries of the Anterior Segment
Injuries Caused by Animal and Plant Substances
Ocular contact with the milky sap (latex) from a variety of trees can cause toxic reactions manifested by acute keratoconjunctivitis, epithelial defects, and stromal infiltration. The pencil tree and the manchineel tree, widely distributed in tropical regions, are known offenders. Houseplants in the genus Dieffenbachia are known to cause keratoconjunctivitis from calcium oxalate crystals in the cornea; crunching the leaves can cause these crystals to shoot into the cornea. The crystals cause a foreign-body sensation and are difficult to see on slit-lamp examination; the diagnosis of Dieffenbachia keratitis is made from the history as much as anything else. Corneal foreign bodies from coconut shell, sunflower stalk, and ornamental cactus have also been documented.
Initial management of injuries caused by all such plant materials should include irrigation and removal of foreign bodies when possible and administration of topical cycloplegics with prophylactic antibiotic coverage, as indicated by the clinical situation. Corticosteroids are best avoided, as they suppress immunity to microbes in general and may promote fungal infection specifically, which is of concern in all cases involving vegetable matter because plant sources are common causes of fungal keratitis. Surgical removal of vegetative foreign bodies should be attempted in order to mitigate the inflammatory response or associated secondary microbial infections. If a patient with a severe injury from plant sources fails to improve after supportive therapy, the possibility of bacterial or fungal infection should be considered and appropriate workup (including culturing and/ or biopsy) performed. For additional discussion of microbial keratitis, see Chapter 10.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.