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A 39-year-old man with blindness following the application of raw cassava extract to the eyes
Digital Journal of Ophthalmology 2009
Volume 15, Number 2
May 30, 2009
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Abdulkabir A. Ayanniyi, MBBS, FMCOph | University of Ilorin Teaching Hospital, Ilorin, Nigeria
Diagnosis and Discussion
Various substances are used as traditional eye medications across the globe, including organic and inorganic substances.(1) Unfortunately, harmful substances including raw cassava extract (as illustrated by this case and anecdotal reports), which are potentially toxic to ocular tissue, form the bulk of these substances.(2,3)

The deleterious effects of harmful traditional eye medications on vision have been widely reported.(4,5,6) The process leading to visual loss by traditional eye medications could be either by chemical burns to the ocular tissues, innoculation of harmful pathogenic organisms, or both.(7)

The patient in this report had failed self-medication using eye drops bought from a local chemist. The drug could have been steroid-based, worsening possible particulate foreign-body-induced corneal erosion especially in the right eye.

Both the patient and the priest were ignorant to the ocular condition, as their actions at least raised false hope and at most only provided psychological support. Most likely, the low level of education and low socio-economic class of the patient also contributed to his penchant for unorthodox treatment options. Perhaps, it could be argued that the lack of a readily accessible standard eye health care in the community was another compelling factor to the patient’s decision to seek unorthodox treatment.

In this patient, the treatment objective was to remove or dilute toxic cassava extract and purulent ocular discharge, to relieve pain, and to cover for pathogenic agents (bacteria and fungi). Other treatment plans were to provide psychological support, education of the patient and his relatives (who accompanied him to the hospital) on the danger of self medication and, of course, to rehabilitate the patient. Further management as well as ocular assessment could not be carried out as the patient was lost to follow-up after the fourth day.

The patient history, ocular examination findings, and negative culture results suggest chemical ocular injury. Raw cassava is not only acidic (pH 6.5) but also contains cyanide, among other constituents, that are potentially toxic to ocular tissue.(2,3) However, the speed of progression might have been accentuated by other insults, including particulate foreign bodies (which could have breached the corneal epithelium), pathogenic organisms, and unknown eye drops. The eye drops applied by the patient might have contained steroids, which would inevitably worsen the progression of any existing corneal erosion and infection. However, this could not explain the absence of an isolate in culture. On the other hand, an eye drop containing antibiotics is unlikely to worsen the progression of any existing corneal erosion and infection but could explain the absence of isolate on culture.

Raw cassava extract, based on its constituents, can cause chemical burns to the eyes with rapid destruction of ocular tissue leading to blindness. However, other added ocular insults may have served as catalysts to the cassava extract-induced ocular damage. Eye health education targeted toward agrarian communities on the danger of self eye medication including the use of traditional eye medications, especially raw cassava extract, will reduce avoidable blindness in the community.