Subject: US: Cannabis Can Affect Vision Say Scientists 



Source: The Daily Telegraph (UK)



Pubdate: 7 December 1999 





Cannabis Can Affect Vision Say Scientists

By Roger Highfield, Science Editor

 

A FAMILY of chemicals that includes the "psychoactive" ingredients of

marijuana plays a role in vision, scientists have found. The discovery

sheds new light on claims by Caribbean fishermen that a rum-cannabis punch

helps them see in the dark.



For the first time, "receptor" proteins activated by this family of

compounds - cannabinoids - have been reported in the eye, providing a

missing link in efforts to understand the retina. The work also provides

greater understanding of the effects on vision of marijuana and hashish,

suggesting that reports of the perception of a "snowy" visual field,

increased light intensity and altered vision may be due to effects in the

retina, rather than the brain. It may even explain why Jamaican fishermen

claim that a punch made of cannabis mixed with rum aids night vision.



"The scientific literature on marijuana, the known effect of cannabinoids

in other parts of the brain and the places we find the receptor in the

retina all make plausible the notion that cannabinoids may well have an

effect on light sensitivity or light-dark adaptation," said Alex Straiker,

of the University of California, San Diego.



However, the retina is "incredibly complex", so this remains only a

possibility, said Mr Straiker, principal author of the report on the

prevalence of receptors - docking points for cannabinoids - in the retina.

The paper appears today in the Proceedings of the National Academy of Sciences.