A mysterious post-operative eye disease that swept across the continent has shut down one of Toronto's busiest cataract surgery centres.
It causes an inflammation in the eye's interior, which can go away on its own or, in more severe cases, cause torn or detached retinas, a form of glaucoma and vision loss.
The Scarborough Hospital, which performs some 5,000 of the eye operations a year, cancelled all cataract surgeries after more than a dozen patients came down with the ailment, known as toxic anterior segment syndrome, or TASS.
Dr. David Wong (a University of Toronto ophthalmologist and a retinal surgeon), has helped launch a national TASS network to track cases and try to pinpoint possible causes.
Evans said TASS has affected about 137 eye centres across North America in the past 18 months and almost all of them have had trouble targeting a source.
TASS is not bacterial or viral in origin, but occurs when toxins enter the eye's anterior segment, which runs from the lens outward to the cornea. That is precisely the area that is invaded during cataract surgeries, when a clouded lens is replaced with a plastic one.
Potential culprits have ranged from surgical instrument cleansers to antibiotic injections.
Wong likened the search to "looking for a needle in a haystack" and said that many different products may be at play.
He said the enzymes used in surgical instrument cleansers, for example, may change without notification and that those new agents may cause a reaction in the eye.
Furthermore, he said, these new enzymes may cause inflammation in some eyes and not in others, making epidemiological tracking harder still.
Other potential agents include antibiotic injections, whose contents can also change without a surgeon knowing, saline solutions or even tap water used to rinse the instruments.
Wong said other types of eye surgery may also cause TASS, but it is most noticeable after cataract operations mainly because highly refined surgical techniques have reduced post-operative inflammation.
So when inflammation does occur after cataract surgeries, doctors are quick to take note of it, which may be why the syndrome is being identified in increasing numbers.