For the most part, he said, those steps are there because people do well with them, and they don't sacrifice quality of life.
"But, we don't want those restrictions. We want to put whatever astigmatism we want at whatever orientation."
Applegate explained that although rigid contact lenses, or gas-permeable ones, are used to correct higher-order aberrations in highly aberrated eyes by masking a significant portion of the aberrations, soft lenses are preferred by patients about 3-to-1, because of comfort and wear time.
"The major problem with the rigid gas-permeable lens is the patient often has to pick the portion of the day that they're going to have reasonable vision," Applegate said.
The key to creating a custom soft lens, he said, is making the surface that corrects the optical errors of the eye and having it remain properly aligned during wear.
"You can imagine that you have a surface with bumps and hills on it, and they're on the order of microns. If there are bumps and hills, light will go every which way. Instead of a clean focus, it's a very blurry focus," Applegate said. "The correcting bumps and hills of the contact lens have to register perfectly with the bumps and hills on the eye.
"First, we have to manufacture this lens. The success of this lens depends on registering it on the eye. It can only translate left and right on the order of one-tenth of a millimeter, and it can't rotate more than a couple of degrees."
A large part of Marsack's latest grant is dedicated to solving lens-stabilization problems.
"It's important to know how it's going to rotate, so that, when you put the correction on it, you'll know how it'll perform," Marsack said. "It needs to move so that it's physiologi
|Contact: Angela Hopp|
University of Houston