Night Vision

[jjrakman]

It's known that astonomers use red flashlights and planes have cockpits lit with red light, in order to preserve a person's night vision.

 

So if red light preserves night vision, would an ultraviolet flashlight do the same, if it's on the other end of the spectrum?

 

What effect does ultraviolet light have on a person's night vision?

[tomgwyther]

I tried this experiment myself, accidentaly whilst working in theatre.

 

We had to use either red or blue filters for near stage applications so they wouldn't interfere with the main effect of the stage lights.

 

Red works best for most people. It's still dark but you can clearly make out printed paper (Musical score) and the equipment around you.

 

Blue is not bad, but it's more difficult to see what your doing.

 

Once, the only filter I could find was a UV gel.

1. I could only see things that were pure white, every thing else was black.

2. I felt physicaly ill, and nearly threw up!

 

The Lighting engineer later explaned that 'They never use purple or UV gels backstage, as it makes the crew bring up their breakfast!'

 

I'm not sure exactly why purple or UV light makes you nausious, it just does.

[swansont]

Night vision is tied to the chemical rhodopsin, found in the rods, which breaks down more readily with shorter wavelengths. So UV will not tend to preserve night vision.

[Glider]

Plus, true UV is very bad for your retinas.

[jjrakman]

Night vision is tied to the chemical rhodopsin, found in the rods, which breaks down more readily with shorter wavelengths. So UV will not tend to preserve night vision.

 

So UV light retards or prevents rhodopsin from covering the rods, thus creating poor nightvision?

 

Plus, true UV is very bad for your retinas.

 

Can you explain the effects?

[foodchain]

 

 

 

Can you explain the effects?

 

Its like staring at a running light bulb basically, except you don’t see the light as you would on wavelengths that we can see "visible" light.

IN the middle school the teacher had to spell that out for us as some people were staring directly into a source of such and talking about how the machine was not working.

[Glider]

Can you explain the effects?

 

Eye

 

Pathological responses of the human eye to excessive UVR exposure include photokeratitis and photoconjunctivitis (inflammation of the cornea and the conjunctiva, respectively). Repeated exposure is considered to be a major factor in the causation of non-malignant clinical lesions of the cornea and conjunctiva such as climatic droplet degeneration (discrete areas of yellow protein deposits in the cornea and conjunctiva), pterygium (an overgrowth of the conjunctiva on to the cornea) and, probably, pinguecula (small yellow growths in the conjunctiva). Damage can result from exposure to UVA, UVB and UVC.

 

There is epidemiological evidence that chronic exposure of the eye to intense levels of UVR contributes to the development of cortical cataract. Evidence for a causal role of solar radiation in macular degeneration (a major cause of blindness) is conflicting. The extent to which UVR exposure is an important risk factor for cataracts in the general population is unclear, as is its relation to eye melanoma.

 

There is good evidence that prolonged gazing at very bright light sources, particularly those emitting shorter wavelength blue light, causes retinal damage resulting in transient or permanent loss of visual acuity. Staring at the sun can damage the retina permanently. Such an effect would normally be prevented by the natural aversion response invoked by looking at a bright light, but this response can be intentionally suppressed. Similar damage has also been induced in the non-human primate retina following acute exposure, particularly to blue light. It is not clear to what extent UVA is involved as its transmission through the lens is low in adults but is higher in children.(bold added) (Documents of the NRPB: Volume 13, No. 1. Health Effects from Ultraviolet Radiation: Report of an Advisory Group on Non-Ionising Radiation.).

[swansont]

So UV light retards or prevents rhodopsin from covering the rods, thus creating poor nightvision?

 

My understanding is that rhodopsin is a chemical in the rods, and needs to be present to see in low-light conditions. Light breaks it down but red is least effective at doing this, so dim, red light will not tend to disrupt night vision. The rods are there for peripheral vision and detection of motion and do not detect color. Color is detected by the cones in the center. So the dim, red light lets you see stuff with the cones, without disrupting/depleting the rhodopsin buildup in the rods.

[jjrakman]

My understanding is that rhodopsin is a chemical in the rods, and needs to be present to see in low-light conditions. Light breaks it down but red is least effective at doing this, so dim, red light will not tend to disrupt night vision.

 

So that would mean that UV light would break down rhodopsin significantly more, is that right?

[Fuzzwood]

Yup as UV is prone to make radicals out of all sorts of stuff. I guess it's the sheer amount of energy put on the rhodopsin that breaks it down.