Topically applying alpha-linolenic
acid (ALA) can ease the symptoms of dry-eye syndrome,
according to American researchers.
Dry-eye syndrome causes distress to the eyes, damage to
the cornea and insufficient tear flow and affects about 10
million Americans who are mostly women. It occurs more
often among people with a history of arthritis, gout,
diabetes, thyroid disease and smoking.
The researchers, Saadia Rashid at the Schepens Eye
Research Institute in Boston, Massachusetts, and Professor
Reza Dana, the director of the Massachusetts Eye and Ear
Infirmary Cornea Service, found the application of ALA
drops led to a reduction in the symptoms of dry eye
syndrome in mice.
"The current study for the first time demonstrates the
benefit of topical application of a particular fatty acid
in treating the signs of dry eye syndrome at both the
molecular and cellular levels," said Dr Dana.
"Using topical formulations of fatty acids to treat dry
eye would allow for more flexibility for treatment,
including lessening side effects that patients can
experience from oral intake of fatty acids. Clinical
studies with topical fatty acids are being planned, which
if successful could alter the method by which this common
condition is treated."
ALA is a long-chain omega-3 fatty acid traditionally
associated with heart health benefits. It cannot be made
in the body and is commonly found in canola, flax, soy,
perilla, and walnut oils.
The study, published in the February issue of the Archives
of Ophthalmology, tested three formulations of fatty
acids: 0.2 per cent ALA; 0.2 per cent linoleic acid (an
omega-6 fatty acid) and 0.1 percent alpha-linolenic acid
combined with 0.1 percent linoleic acid.
One of the three formulations was applied to the eyes of
mice for ten days with measurements taken every 24 hours.
A control group received no drops.
ALA benefits
Those treated with the pure ALA showed a 45 per cent less
corneal damage than untreated eyes and those treated with
linoleic acid after five days. Those treated with the
combination dose also showed significant reduction in
symptoms.
By day 10, those mice receiving ALA showed a 71 per cent
improvement compared with the untreated and linoleic
acid-treated group. However the mice receiving the
combination treatment had their earlier gains reversed.
Overall, treatment with ALA significantly reduced the
number of immune cells derived from monocytes and
macrophages on average 40 per cent in both the centre and
periphery of dry eye corneas, compared with controls and
other treatment groups.
The researchers found expression of the pro-inflammatory
mediators IL-1α and TNF-α in the corneas exhibiting dry
eye syndrome showed slight increases in IL-1α production
from day two to day 10, but large and significant
increases in TNF-α production by days five and 10,
compared with baseline and day two. The cytokines IL-2,
IL-6 and IL-10 were not detected in dry eye corneas.
In contrast, the conjunctiva - the lining of the eyelid
and eyeball excluding the cornea - showed significantly
increased cytokine expression in dry eye syndrome, with
increases varying from 5-fold for IL-2 to 98-fold for
IL-10 by 10 days.
Treatment with ALA, but not with any other fatty acid,
resulted in a significant decrease in IL-1α at day 10 and
TNF-α at day five. |
