Re 'Glaucoma' (WDDTY vol 15 no 12), the preservative in many eyedrops is benzalkonium, which contains a benzene-related chemical that is well documented to cause bone-marrow damage. In a report published in Ophthalmology (2001; 8: 74-80), it states that eyedrop preservatives can cause toxic inflammatory changes of the ocular surface, dry eyes, cell death, etc. Xalatan glaucoma eyedrops contain more of this chemical than most.
Perhaps preservatives could be reduced if manufacturers instructed patients to store drops in the fridge, as they probably add extra preservatives to enable them to be stored at room temperature. Alternatively, drops can be kept bacteria-free for a week or two, so why don't manufacturers supply them in smaller bottles lasting just a week? Then they could omit preservatives altogether.
A new preservative, Purite, a stabilised oxychloro complex, dissipates into the natural components of tears, and so is much less toxic and more suitable for long-term use. - Ann Wills, via e-mail