PRK enhancement after LASIK... Almost imperceptible improvement after 4 months

I had LASIK surgery in 2003 in both eyes which corrected me to 20/20. After 10 years, my near sightedness gradually regressed to roughly 20/40 or 20/60. I decided to consider an enhancement, and went back to my original surgeon, who recommended PRK this time, one eye at a time. I underwent the surgery in my left eye in November 2013. Nearly four months later, best case, the improvement in my left eye has been negligible. Should I be concerned? What questions should I ask at my next appt.?