Eye Drops For Cataracts?
An old eye drop maybe making a new comeback. Pirenoxine, also known as Catalin in Japan, was the subject of a recent study in China.  The study tested the ability of Pirenoxine (PRX) to inhibit cataract formation in test tubes. The test tubes contained crystallins, a protein found in the lens inside the human eye. PRX appears to act by binding calcium and selenite ions. Both of these ions have been shown to contribute to cataract formation in the cortex (inner layer of the lens) when they are elevated. They act to increase the breakdown of the crystallins protein structure. By binding these ions the rate of of cataract formation in the test tubes was decreased by 38%.
Cataract Prevention Eye Drops In Use Since 1958
These eye drops have been used by eye doctors in Japan since 1958. A study in 2006 questioned why Japanese eye doctors are prescribing Catlin since there was no significant supporting evidence. It has been thought to be a placebo type of treatment that has been widely adopted. Numerous companies have manufactured pirenoxine overseas under a variety of trade names. Both Allergan and Alcon have made versions of pirenoxine. Takeda is a large phamaceutical company in a number of other countries. Santen, Ferron, and Farmigea all produce a brand. Clarvisan, Clarvisor, and Baineiting are some of the different brands that can be found around the world. There is no FDA approved eye drop in the United States at this time.
Problems With Cataract Prevention Eye Drops
There are several potential problems with the PRX eye drop medications. Research has not yet shown any effectiveness for treating or preventing cataracts in the living eye. Another significant issue lies in the solution used to deliver the drops to the eyes. Thimerosal is used as a preservative in common preparations of this eye medication. Thimerosal is a derivative of mercury, and has a fairly high rate of allergic reactions. It also is mildly toxic to the cornea tissue of the eye, and may cause undesirable long term changes when used on a chronic basis.
We should see more research in the future that addresses both of the problems above. Hopefully we will have a new treatment for cataracts not too far down the line.
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Inorg.Chem. 2011, 50 (1), pp 365–377
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Sekimoto M, Imanaka Y, Kitano N, et al. Why are physicians not persuaded by scientific evidence? A grounded theory interview study. BMC Health Serv Res 2006 Jul 27; 6:92