Seizure protection in a bottle!Posted: 04/27/2012
If your local optician can tint eyeglasses, it’s now possible to get protection from visually triggered seizures without ordering therapeutic Zeiss lenses. Lenses tinted using the new Deep Blue Zee lens tint are nearly the same color and appear to be just as effective as Zeiss Z1 F133 lenses.
Brain Power Inc. of Miami, and its UK arm, Brain Power Ltd. of Warwickshire, England, have introduced a cobalt blue optical tint that, according to the company, is nearly identical to the color-filtering specifications of the Z1 F133 lenses used in Capovilla’s photosensitivity studies. Brain Power, which supplies optical tints and laboratory equipment to opticians, optometrists, ophthalmologists, and lens manufacturers, developed the Deep Blue Zee tint specifically for photosensitivity protection. BPI describes itself as the world’s largest manufacturer of optical tints, chemicals, and instruments.
My daughter has been wearing a locally tinted pair for the past week and is finding them quite effective. She actually prefers them to the Zeiss because they aren’t quite as dark and therefore don’t darken her entire view as much. Because they’re not as dark, she is still able to see when watching DVDs from farther away from the screen.
The therapeutic properties of the Z1 F133 lens are due to its color and the way it blocks out shades of red. The amount of light a lens lets in across the color spectrum is measured by a spectrometer and shown in a spectrum curve (see graphs below), and each lens color has a unique spectrum curve. Capovilla and colleagues tried many colors and lens types before settling on the cobalt blue shade that lets in very little light in the red part of the spectrum. The big dip in this graph, excerpted from Capovilla’s 2006 study, shows that very little light is transmitted through the lens in the range of red wavelengths, measured in nanometers.
This is the Z1 spectrum curve from the Capovilla studies:
For the tint to be absorbed properly by the lens, the lens needs to be made of a particular plastic lens material, a plastic called C-39. If you have existing lenses you’d like tinted, they need to be made of CR-39 and can’t already have a hard coating that would prevent the lens from absorbing tint. BPI recommends that the lens be kept in the dye solution for at least 30 minutes to achieve the proper color. According to BPI, after half an hour of immersion in the dye, the absorption process goes more slowly.
As we’ve discovered in the past week, although the locally tinted ones weren’t as dark as the Zeiss lenses, it doesn’t seem to matter. If the lenses turn out not as dark as you’d like, your optician can make them darker by returning them to the dye solution for a little while. The price for tinted lenses will vary depending on the brand/quality of lens that your optician uses. And the quality and effectiveness may vary as well, depending on the optician’s skill, judgment, and choice of lens manufacturer.
The same day we got the new clip-ons, I had the idea that Alice might be able to watch certain DVDs (no anime!) on a small screen without needing to take so many breaks. She is doing well watching DVDs on a portable 7-inch DVD player. She sits several feet away from it so that the screen doesn’t take up too much of her field of vision. If she sat very close, that would cancel out the advantage of a small image that by its size minimizes the impact of video on her brain.
We now have a spare pair of cobalt blue clip-ons, allowing us the opportunity to compare the two side by side. Can you tell which is which?