by 6502programmer » Wed Mar 26, 2008 9:09 pm
I can only speak from my own experience and research, so consider this simply as a data point, not a complete opinion.
Regarding dry eye, yes, your research and mine line up that the more shallow the procedure in the cornea, the less the risk of dry eye. Additionally, dry eye seems reduced with surface ablation.
GASH is always a risk, but from what I was able to find, wavefront-guided ablation not only has a lower risk of inducing higher order aberrations, but also may be able to correct them.
For me, with high nearsightedness (-6.5,-7.0), moderate astigmatism, and moderate HOA's, wavefront-guided was the best approach. The first provider I saw was gung ho on LASIK. The second provider said I was not a good candidate because of the amount of correction and low-normal corneal thickness. After finding out about the PRK surgery, as well as the lasers at the provider, I started doing my research.
They use a VISX Star S4 for wavefront-guided patients. The process starts when they do the scan. The eye is scanned and mapped relative to the iris. This is transmitted to the laser for the treatment plan. During the surgery, the position of the iris is used to guide the ablation. It's tracked 4000 times per second, allowing it to compensate for minute movements.
Often, the visual complications of refractive surgery are due to one of two things: flap complications and decentered ablation. The former, something goes wrong, whether during flap creation or healing, that disturbs the optical properties of the cornea. In the latter, the surgery is done "off center". From what I could find, the laser used for my surgery minimized that possibility.
I chose PRK, though one provider was willing to do LASIK, to eliminate the first case's complications, and went with wavefront-guided to reduce the possibility of the latter. There is some research out there that indicates the clinical results achieved with wavefront-guided correction are better, both in terms of straight acuity (how many letters can you read on this line), as well as quality of vision, particularly at night. There is some research that PRK is mildly better, from a clinical results perspective, than LASIK as well.
I never suffered dry eye before (even with regular constant contact usage), and now, 6.5 weeks post op, do so only from time to time. My vision is outstanding, both in acuity (20/20) and quality (no signs of GASH at all).
I can say that unless you're ready for about a week of "bad contact days", approach PRK with trepidation. That first week was NOT fun, with the first four days being spent doped up with Tylenol III and the next week and a half after that putting artificial tears in every twenty minutes. Add to that I suffered a couple of (extremely painful) epithelial tears that required more visits with the doctor, it was not a pain-free affair.