Unilateral, dilated unresponsive pupil may be secondary to a wide range of ocular and neurological disorders. "Gardener’s pupil" is a pharmacological mydriasis caused by exposure to plants containing alkaloids. We report a case of mydriasis related to Datura inoxia, and detail a number of plants that have toxic effects. This report emphasises the importance of accurate history taking when evaluating fixed dilated pupil. We recommend that labelling of such poisonous plants should detail the local and systemic effects of accidental exposure, rather than merely the fact that they are poisonous.
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Unilateral, dilated unresponsive pupil may be secondary to a wide range of ocular and neurological disorders. “Gardener’s pupil” is a curious pharmacological mydriasis caused by exposure to plants containing alkaloids such as scopolamine, hyoscyamine, and atropine.1,2 We report a case of mydriasis related to Datura inoxia.
A healthy 76 year old white male presented with a unilateral fixed dilated pupil, associated with blurred vision, noted 2 hours earlier. There was no accompanying headache, diplopia, or other neurological symptoms. Past medical history was unremarkable. Inadvertent self medication was denied.
General and neurological examination was normal. Visual acuity measured 6/5 and 6/6 in the right and left eyes respectively. The anterior segments and fundi were unremarkable, and ocular movements were full. However, the left pupil was dilated and unresponsive to both pupillary light reflex (direct, consensual) and accommodation reflex.
Topical pilocarpine 1% induced normal constriction of the right pupil but had no effect on the left, confirming the pharmacological basis of the left mydriasis.3
The patient subsequently recollected cleaning his indoor plants (which included Datura inoxia) earlier that day. Pupil size returned to normal over the next week and accommodation shortly thereafter.
A wide range of plants and plant products are potentially lethal, with local and systemic effects. Ocular side effects may be alarming, particularly when the pupil is dilated (table 1) with blurring of vision. Datura inoxia is not indigenous to the UK, though other members of the genus do grow in the wild. Related species (Brugmansia) are popularly grown in gardens in the UK for their beauty and fragrance. Datura is, however, poisonous, containing the alkaloids scopolamine, hyoscyamine, and atropine. These alkaloids mediate parasympatholytic effects secondary to muscarinic blockade.
Ocular toxicity occurs through inadvertent topical administration, while systemic side effects (primarily tachycardia due to a vagolytic effect4) occur through absorption of the alkaloids from the lacrhymal passages. Systemic effects are more pronounced upon oral ingestion. Although Datura is an outdoor plant, it is not fully hardy in the UK, so is moved indoors during the winter, with consequent risk, particularly to children and adolescents.5,6 The simple measure of instillation of topical pilocarpine 1% establishes the pharmacological nature of the condition and obviates the need for expensive neuro-imaging. Pilocarpine is competitively inhibited by alkaloids such as atropine, paralysing the iris sphincter.
Although accidental mydriasis is commonly due to parasympatholysis, it may also occur secondary to increased adrenergic stimulation (table 1). Care should therefore be exercised while interpreting a pilocarpine test.
This report emphasises the importance of accurate history taking when evaluating fixed dilated pupil. Retailers of such poisonous plants should detail the local and systemic effects of accidental exposure, rather than merely labelling a plant (non-specifically) as poisonous.