Bill Harvey: Sweet leaf

Way back in my Moorfields days, I remember stories of little old ladies being stopped at airports while carrying large lumps of cannabis resin. After confirming the drug was for treating their glaucoma, they were invariably released. I always thought these tales were as apocryphal as the perennial favourite about the rigid contact lens wearer who continued to suffer significant lens deposition despite drinking one protein removal tablet in a glass of water each day.

Interest in the subject first took hold in the early 1970s after one study, designed to look at the impact of smoking cannabis upon the visual system of healthy volunteers, found that just 2g of cannabis lowered intraocular pressure. In some, the drop was as much as 45%. Subsequent studies confirmed that around 65% of glaucomatous eyes will experience a 30% pressure reduction after cannabis inhalation.