Lens Questions: What Sunglasses To Order For Retinal problems

[Bobb]

Hello:

I'm a retired optical engineer, but am still having a hard time obtaining information on the following. If anyone has a spare few minutes, would be most appreciative for any wisdom on the following:

I have significant retinal problems in both eyes, so am really concerned about UV protection.

a. My first question concerns CR-39 for the polarized, single vision, prescription, sunglasses I wish to order:

Is the clear catalytic dye used to extend the UV A and UV B absorptions to
approx. 400nm "usually" added to the monomer when they make the plastic
sheets, or is it just a surface coating on the front or rear surface (or I guess another possibility might be inside the sandwich where the polarized sheet is located)?

b. Do ordered lenses automatically come this way with the UV protection(s)?

c. Can I safely assume that any prescription sunglasses I order will be
CR-39 or polycarbonate, and not acrylic?

d. Same question as (a) for Polycarbonate and/or Glass lenses.

e. Is it worth it in your opinion trying to find someone to make them out
of Polycarbonate for me rather than CR-39(for their UV protection, if truly better)?

f. Or, in Glass? (is there any/much UV A and UV B protection inherent in
the basic glass usually used?)

g. Any strong pro and con opinions on the Photochromic type of lenses?
Do they work well in cars?
I am asking as I believe they work on UV, and the cars glass would cut out a significant amount of UV, I would think?

It seems they also come now in plastic (I'm not sure which) and glass.
Particularly wondering about the UV A and UV B protection they afford?

Unofficially, are the Maui Jims and Action Optics worth the very high $$$ costs, in your opinion?
I guess you are paying for the A/R and hydrophobic coatings. Is the A/R worth getting; do they scratch or come off easily; I think they are on the surfaces, not inside the sandwich.

What brand lenses would you suggest I order, with my retinal problem concers?

Much thanks; appreciate your time.
Bob rgsrose@tiac.net

[Jackie L]

Bobb..............that is pretty tall order to fill. I suggest you seek out a licensed, qualified Optician and sit down with them to discuss your optical and lifestyle needs. It sounds like you have been out of the loop for a bit. Lots of new technology and materials out there today. Good luck to you.

Jackie O

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Still a Maina for now

[Bev Heishman]

Polycarb polarized lenses should do most of what you are requesting in the UV wavelengths.

Retinal problems usually mean we need to block blue light wavelengths. The Melanin lens(Specialty Lens) may fit your bill. They will provide contrast.

I have fit many patients that have had anatomical or physiological problems and have used colors or tints that they prefer such as grey or brown that makes them feel comfortable with the addition of a flash mirror or solid (cut's IR) and a back surface AR coat. Demo lenses will allow you to experiment.

NACL coating labs has a web site regarding their Solar Radiation Control Lenses. They are great lenses that do work. Once a patient experiences a lens like this they ask for it again.

Keep in mind that the darker the lens tint is the more noticeable the back surface reflections are.

[Darryl Meister]

Hi Bob,

a. & b. All plastic lens materials inherently absorb a large amount of ultraviolet radiation. High-index plastics and polycarbonate both generally absorb 100% of both UVA and UVB. Standard CR-39 lenses usually absorb 100% of UVB and anywhere from 85 to 95% UVA. (The cut-off for UVA is accepted to be 380 nm for ophthalmics.)

An additional UV treatment (or "dye") may be added later to achieve full UV protection. This treatment penetrates the outer surface of the lens blank -- but deep enough not to scratch or wear off. (Some hard coatings may also have UV-inhibiting properties.)

c. I'm not aware of any prescription lenses made from acrylic in the U.S. (Some European countries may still make "Perspex" or "I-Gard" lenses available.) Some materials -- particularly high-index materials -- may use a combination of acrylic and urethane resins though.

d. As described above, polycarbonate lenses absorb all UV radiation. Glass absorbs some UVA and some UVB, but a tinted, photochromic, or coated glass lens would be necessary for full UV protection.

e. & f. The previous comments should sum this up. Lens materials can often be treated with additional UV protection, even if they don't initially absorb all of it. The selection of a lens material should be governed by several other facts as well, including thickness, weight, impact resistance scratch resistance, designs, etc. Also, as Bev pointed out, some clinicians feel that additional color filtration may be beneficial to reduce the "blue light hazard" when retinal damage is involved. These lenses often have an amber hue to them (since they are cutting out the blue end of the spectrum), and may distort color perception to some extent.

g. Yes, photochromic lenses generally darken somewhat within automobiles, but not a lot. As you pointed out, the laminated glass windshields absorb much of the radiation necessary to activate the lenses. How dark the photochromic lenses get inside a car will depend upon the specific type of photochromic material. There are several popular plastic photochromic lens materials available now.

As pointed out in earlier postings, a qualified optician can discuss the specific advantages and disadvantages of various materials, treatments, and designs -- as well as make some sound recommendations based upon your particular visual requirements. A one-on-one conversation, complete with some lens samples, might give you a better perspective on your options.

Best regards,
Darryl