More than meets the eye

The ocular lens does more than refract light and filter UV, it also releases antioxidants – in rats at least.

University of Auckland, New Zealand researchers discovered that lenses of the rodent species released the antioxidant glutathione.

The finding follows on from other research showing that the lens absorbs and metabolises oxygen in the human eye, to reduce oxidative damage to tissues.

University of Auckland research fellow, Dr Julia Lim, told OT that: “We cultured rat lenses in artificial aqueous humour under low oxygen conditions to mimic the ‘natural’ environment that the lens would sit in.”

In the research published in the journal Experimental Eye Research, the team measured the changes in the artificial aqueous humour, and found, one hour later, higher levels of glutathione and adenosine triphosphate, which is thought to activate a signalling system to alter the outflow of aqueous humour in the eye.

Dr Lim emphasised: “For us, this was an interesting finding as it showed that the lens is an active and dynamic tissue capable of modifying the ocular environment.

“The release of antioxidants by the lens could therefore be another antioxidant defence strategy to protect neighbouring tissues from oxidative stress and damage,” she explained.

However, Dr Lim cautioned that: “I cannot be confident that what might happen in rats is happening in human lenses. Glutathione is present in the human aqueous humour, although at much lower levels compared to rats. It is possible that the lens may be the source of this glutathione.”

She highlighted that until conclusive evidence was found in humans, it was premature for any recommendations to be made for patients undergoing clear lens extraction or cataract surgery.

“My view is that if a patient requires cataract surgery, young or old, the best way of treating this is still by way of surgery,” she concluded.

Institute of Optometry research director, Professor Bruce Evans, told OT: “This paper is a salutary reminder that there is still a great deal about the eye that still we don’t fully understand and a conservative approach to interventions, especially non-reversible surgery, is sensible.”

Image credit: Rakesh Rocky