Misadventures with ultraviolet light

Philip Jackson (p.jackson@nla.gov.au)
Fri, 7 Jul 1995 19:32:50 +22303754 (EET)

"The ordinary clinical picture of photokeratitis follows a characteristic
course. After exposure, there is a period of latency varying somewhat
inversely with the amount of exposure. The latent period may be as short
as 30 min or as long as 24 hr, but is typically 6 to 12 hr.
Conjunctivitis, often accompanied by an erythema of skin surrounding the
eyelids, is associated with the sensation of a foreign body or "sand" in
the eyes, varying degrees of photophobia (intolerance to light),
lacrimation (tearing), and blepharospasm (spasm of the lid muscles).
Corneal pain can be severe. The individual is usually incapacitated for
some period of time. These acute symptoms usually last from 6 to 24 hr,
and almost all discomfort disappears within 48 hr. Very rarely does
exposure result in permanent damage." (UV-A: Biological Effects of
Ultraviolet Radiation with Emphasis on Human Response to Longwave
Ultraviolet, pp. 177-8).

Still, better safe than sorry. Walter B. Woodbury, in "The Electric Light
in Photography: A Warning," (The Year-book of Photography and Photographic
News Almanac for 1883, p. 87), relates his experience of temporary
blindness after spending four or five hours printing ordinary silver
chloride paper with an arc light in 1866: "I was told that the white part
of the eye was simply a mass of blood." The next day Woodbury regained his
sight, but at the time of writing "my sight has rapidly deteriorated, not
in the usual way, that is called old sight coming on, but in the form of a
white glare or spot covering the centre of vision, so that, as I write
this, the word I am writing only becomes visible when I get to the next
one, spectacles being of little avail. Reading has also become entirely
out of the question. I can only conclude that the centre of the retina has
got damaged by the image of the strong arc lights, much in the same way as
a piece of brown paper is set on fire by condensing the sun's rays on to
it."

The misadventures of William Friese-Greene and Walter B. Woodbury almost
belong in one of Hilaire Belloc's cautionary tales, if this "light"
subject wasn't so serious. I don't mean to put you off, but but anybody
using intense artificial sources of ultraviolet light should be aware of
the dangers.

Take care,
Philip Jackson
pjackson@nla.gov.au