Standard LASIK involves correcting refractive error (myopia, hyperopia or astigmatism) as calculated through lens elements utilized in standard eye care refractions. Custom LASIK involves using sophisticated tools known as aberrometers which use near infrared light to determine how your eye alters light layer by layer as it travels through the elements of your eye. Standard lenses are available in steps that vary by a quarter unit. Aberrometers can measure differences smaller than the quarter unit, thus are more precise tools for measuring refractive error. If this is the case, the decision as to which method should be used during your LASIK procedure should be a slam dunk; it sounds like a much more precise outcome would result from use of measurements taken by aberrometers and custom LASIK to correct for them. The problem is that the eye is in a dynamic state it is constantly changing. Today's aberrations will differ tomorrow, next week, next month and years from now. The elements of the eye through which light pass include the tear layer, the cornea, the aqueous, the lens of the eye, the vitreous and the retina. The cornea, the lens and the retina are relatively static and there may be benefit for Custom over standard lasik if a majority of the eyes aberrations are located within these structures, but aberration technology is not advanced enough to determine which tissues are causing the aberrations. If the aberrations within your eye are being caused primarily by your vitreous, you might achieve a very high level of vision correction with custom lasik for the first 6 months, but as your vitreous changes, you will lose some of the benefit of the custom procedure. Same thing with your tears; each blink changes your wavefront. The wavefront measured before a blink is different after a blink. Also the wavefront of your eye is measured by the aberrometer prior to having a flap created. Creation of the flap totally alters the measured wavefront, so what benefit are you actually receiving from the custom procedure? Unless your aberrations are mostly in the lens or the retina of your eye, the benefit is likely limited. Surgeons often charge up to $1000 more for custom LASIK than they do for standard LASIK, so with a questionable benefit the patient needs to decide whether the cost will provide the benefit they hope to achieve.
Studies have questioned the reliability of some aberrometer technologies:
In myopes, aberrometer measurements were similar to techniques your doctor uses to measure your vision, including accuracy and repeatability. (OVS, vol. 80, 1, January, 2003)
Different aberrometers measure differently ñ no two aberration measurements are the same. Often the ability to measure and correct aberrations exceeds the eye and brains ability to discriminate between them.
Images captured using different lights showed noticeable differences. The largest variations may increase as an eye ages. Different wavelengths, however, provide aberration estimates within the experimental error.
Little if any variability in the magnitude of aberrations of the eye is correlated with refractive error.