Clarification on black light causes blindness myth

[Teelie]

On another board I was told that black light will blind your fish. This is one of those myths like fish growing to the size of their tank or goldfish can be kept in a bowl. There is a grain of truth to it but the truth is buried in the misleading claim itself.

Proof that it can cause blindness? I've found only one explanation and it's been disproven. UV light causes blindness. Yes and no.

Proof it doesn't cause blindness? Read on.

I've heard it gives them cancer too before and as far as I've ever been able to find scientifically or even semi-factually, it's all crap. I think fish are blind to the light spectrum itself but it doesn't cause blindness to normal light waves (as in, they can see just fine when you turn on normal lighting again). I can wave my hand right in front of my Cories and they don't flinch under black light. I tried that under normal lighting afterwards. They ran and hid seeing my hand just fine. I'll look for the visual spectrum fish see tomorrow to be certain. Needless to say though, I believe I'm right.

How Stuff Works has a good article on black light. According to the site, black lights actually absorb the more harmful wavelengths of UV light (the ones which may cause blindness) so the only visible UV is perfectly safe. The fact that all a black light does is basically "remove" regular light so we can see the ambient UV spectrum makes me more skeptical of the blindness/cancer myth.

People with half the information they need are more dangerous than those with none of it. My guess is someone once made the comment black light is blind to fish, it was transposed to it blinds fish and now we have this wild myth running on the loose which has since grown to causing cancer according to at least one person I recall claiming this last year.

So, black light is safe as far as I can tell after digging for anything even remotely credible on it's supposed dangers and coming up blank. A few claims of how UV is dangerous which is true under some circumstances but not these.

 

[andywg]

The belief will more likely stem from the fact that UVC rays can cause blindness. UVA and UVB are far less harmfull (if at all).

 

[Bignose]

There is some ongoing research on this. Searching for "UV light AND blindness" in the web of science, I really only found one article that is relevant:

Title: The photosensitiser xanthurenic acid is not present in normal human lenses
Author(s): Hains PG, Gao L, Truscott RJW
Source: EXPERIMENTAL EYE RESEARCH 77 (5): 547-553 NOV 2003
Abstract: UV light has often been investigated as a risk factor for the most common cause of blindness, human age-related cataract. One mechanism whereby UV light could induce cataract is via the action of photosensitisers. In this regard, xanthurenic acid has recently been highlighted since it has been reported to be present in the human lens and, in model studies, it markedly enhances the photo-oxidation of proteins by wavelengths of light that penetrate the cornea.
In this study we used HPLC and mass spectrometry to examine whether xanthurenic acid is indeed present in human lenses and, if so, the effect of age on its lenticular concentration. Xanthurenic acid could be formed artefactually by incubation of 3-hydroxykynurenine (30HKyn) yellow, a known autoxidation product of the lenticular UV filter, 30HKyn, in the presence of air and light, however, it could not be detected in any human lenses studied. Therefore, it appears unlikely that xanthurenic acid plays a role in lens aging or human cataract.

The conclusions here seem to indicate that nothing in the human lens that would be reactive to UV light. Nothing I could find relates to fish eyes, but given the lack of other evidence from Teelie, it does look like myth.

Teelie, good idea in starting these kind of threads, I always enjoy them. There needs to be much more skepticism and proof presented whenever someone makes broad statements. Not just in fishkeeping, but in general. There was a thread a few days back about astrology -- which has been the subject of numerous studies and every one reduces to the astrologers getting no more right than through pure luck. Yet, a recent survey showed that on the order of 50% of Americans still belive in it. Many members may be too young to remember, but look it up: Nancy Reagan used to consult an astrologer before scheduling the daily meetings Ronald would have. Imagine the (arguably) most powerful man in the world consulting some con-artist before making world decisions. I could go on, but I don't want to stay on my soapbox for too long. Just point a link to One of many pages debunking astrology from a scientific point of view.

 

[Teelie]

Astrologers I think are a step or two above conmen only because the likely believe their claims and aren't knowingly deceiving their victims. But yeah, the idea of someone using astrology or religion to dictate the future of millions or even billions of people really does bother me. History shows what following signs and prophecies results in and it ain't pretty.

Anyhow, on the topic of the UV light and fish eyes, I haven't been able to do any research on it today and tomorrow I have classes so undone homework is taking up my time. Nonetheless, I'll find the truth on the fish eyes.

 

[andywg]

Just did a quick search and found this list of sights relating to the effects of blue light on ocular health from the scholar.google sight:

Google Scholar sites

Also, through google I found this list of research papers on the same subject:

Research papers