[visionlist] Info on "coloured filters" sought

[Prof. Michael Bach]

Dear Vision Friends:

Supposed to write a review on coloured filter glasses ('twas a situation where I couldn't really say no), I have a hard time finding good literature on this. “Good” here means solid science, experiments preferably performed in blinded fashion – to the degree "blind" is possible with tinted glasses :). If this interests you, I would value your input, and specifically on these topics:

• Just my limited English? Search terms "filter", or "colored filter", or "tinted glasses / lenses" or else?

• Contrast: How can contrast improve, when by design there is less information behind a wavelength-selective filter than before it? One exception: short wavelengths suffer more scattering, so removing them can help. But is there more?

• In rod monochromacy (achromatopsy), reducing total light flux by 10–100 times helps by avoiding rod saturation. Orange filters can do that, and have the added “social” bonus that other people can see the eyes. Or is there an additional bonus to orange glasses over strong neutral density filters (with equivalent rod-weighted flux reduction)?

• In various retinal dystrophies (e.g. cone dystrophy or RP), tinted glasses are supposed to help. How does this work beyond "psychology"? Are there reliable experiments?

• A sideline: Does the spectral absorption of the juvenile lens change over, say, 0–10 years of age?

• Why do people with beginning media opacities like sunglasses? The contrast, be it quantified in Michelson or Weber, remains numerically identical. Is it a nonlinearity or “just psychology” (not meant pejoratively)? Methinks head sunshades (visors) would help more.

• “Brightening” glasses. There are types of sunglasses making the world appear brighter. How does that work?

• I'm sure there are many occupation-specific hazards (e.g. glassblower cataract, welder's flash) where filters help. Am I missing something important here?

• I am sceptical about the Irlen-type filters and the buzz (SSS) around them. Are there any reliable, robust findings? [I am _not_ trying to start a *storm!]

• I don't believe you can “cure” colour blindness / deficiency by tinted glasses. [Possible exception: creating interocular differences.]


I apologize for the lengthy post, all ignorance on my side, and value all advice on any of the above topics from you.


With my best regards,
Michael.
-- 
Prof. Michael Bach PhD, Eye Center, University of Freiburg, Killianstr. 5, 79106 Freiburg, Germany. 
Michael.Bach at uni-freiburg.de   <http://michaelbach.de>