What Is the Future of LASIK Technology?
It's obviously always difficult to predict the future, but the next great push in refractive surgery is moving towards "wavefront" technology. Current technology creates an "off-the-rack" laser ablation to correct whatever glasses prescription that is entered into the laser's computer. It is very rare for anyone to have a perfectly smooth cornea without measurable peaks and valleys. These can be shown on a corneal topographic map like the one below and to the left. The areas of similar color should be perfectly circular, but as you can see, there are undulations and differences. This cornea would actually be considered to be quite regular, most are not this regular. Current LASIK surgery flattens the cornea, but any irregularities that were present before surgery will be present after surgery. An example is at the lower right. You can appreciate the center of the cornea is flatter (more blue), but it once again is not a uniform blue color--there is still some irregularity although probably not enough to be bothersome in most daily situations.
Experimentation is currently ongoing with topography-guided lasers, the topographic map information from above would be sent to a computer which would decide the course of the laser's ablation. The laser would shave down high spots more than low spots in order to produce a more smooth and uniform final outcome. Or at least that's how it would work in theory, which leads us to our next section--wavefront scanning.
Wavefront technology is a hot area of current research in refractive surgery. This technology was originally developed by astronomers to reduce aberrations in telescopes and has now been applied to that most personal of telescopes, the eye. Wavefront scanning essentially works like this: a laser is scanned through the pupil to the back of the eye and reflections of the light are collected which creates a map of all of the optical aberrations of the patient's eye. For example, the refractive error is only one type of optical aberration, there are other natural aberrations which cause distortion or glare during everyday visual tasks. If the natural distoration of the cornea and natural lens could be corrected, the retina has the ability to discriminate extremely small points, down to better than 20/10 on the eyechart! That's smaller than the smallest line! These scanners are in their infancy, but some study is ongoing, even coupling these scanners with laser ablation in Europe with some slight improvement over conventional LASIK, but with many improvements to be made. Some of the inherent problems with a wavefront map is that the aberrations of the eye change over time with normal aging, cataract formation, etc. and the aberrations change even during the day when reading, for example or when the pupil changes with different light conditions. Other problems with attempting a wavefront correction is that the current lasik flap induces some slight aberration as well as the unpredictability of how the flap will heal at the cellular level. So, all of this fancy technology may in fact be too good for practicality, or at least has several stumbling blocks before it becomes useful.
But, doctor, when are they going to do something about my reading glasses?
Oh, you can bet that many people are working on a solution to your reading glasses, as this would be a multi-multi-billion dollar industry. One of the stumbling blocks toward fixing problems with near vision (presbyopia), is that scientists aren't even in agreement of why is occurs, or how it even works! It is, however, a fact of life for everyone as they age. Current correction of presbyopia has centered on two different approaches, monovision and multifocal corrections. Monovision is where one eye is made near-sighted (myopic) on purpose in order to read with one eye and see far away with the other. Multi-focal correction uses rings of correction, some for near, some for far away, so that some light rays entering the eye are focused when looking at an image far away, and some rays are focused when looking at something at near. Neither of these replicate what happens in the normal, youthful eye and are thus very limited, although some people do very well with these approaches. The ideal solution would replicate the current lens and its ability to change shape when looking at near objects. Current work is being done to develop a polymer substance that would replace the lens. Other research is going toward different surgical procedures to stretch the area of the sclera where the lens attaches giving the lens more room to maneuver. In either case, much more work is yet to be done.