Hi Elaine
Although most people have very good vision without glasses after LASIK, it is possible for what we call under or overcorrection to occur with any kind of refractive surgery. Even if under/overcorrection occurs, it is usually of such a low degree that the patient does not notice it, or it does not affect the patient in their daily life. These under/overcorrections are usually due to small differences in the way a particular person's eyes respond to the laser effect.
The most important factor to consider, in deciding whether to proceed with enhancement, is how much the blurring caused by the under/overcorrection affects you.
So if for example, you went for a check up and the optometrist said you have residual degree of 50 degrees, but you feel quite happy with the vision you have and any blurring is so mild that it does not affect you, then it is perfectly fine to leave the 50 degrees alone.
On the other hand, if there are things you would like to be able to do but the residual degree prevents you from doing it, then it is quite reasonable to consider enhancement.
The other important factor to consider is the time since the original LASIK operation. It is well known that the spectacle power can take some time to settle down, so enhancements should only be done at least 3 months from the original LASIK. This is to avoid treating patients whose apparent residual spectacle power could have disappeared by themselves.
Generally speaking, 50 degrees is about the threshold where I would consider enhancing a patient's LASIK result. 25 degrees would be such a small degree that it is generally not thought worthwhile to undergo the procedure, while with higher residual degrees such as 100 degrees the benefit becomes more significant.
Of course, even if you are keen to have enhancement, you will need to be checked for suitability with an assessment that includes your remaining corneal thickness. Do discuss these issues with your doctor as well so that any further doubts are clarified.
