The Graf Optical Pre-Operative Evaluation

A comprehensive medical eye evaluation should be performed prior to any refractive surgery procedure.  In addition to the elements of a comprehensive medical eye evaluation, the refractive surgery examination includes the following elements:

Because of the possibility of contact lens induced corneal warpage, patients who use contact lenses should discontinue their use for a period of time prior to the preoperative examination and procedure.  As a general guideline, spherical soft contact lenses should be discontinued for several days, and toric soft lenses and rigid lenses should be discontinued until refractive and keratometric stability has been documented.  Documentation of refractive stability increases the likelihood that the correction will be appropriate in the future. 

Corneal topography should be evaluated for evidence of irregular astigmatism, corneal warpage, or signs of asymmetric steeping, since all may be associated with unpredictable refractive outcomes.

Prior to surgery, pachymetry should be obtained and an estimate of the thinnest residual stromal bed following LASIK should be calculated.  While 250 microns (Um) has been suggested as a safe residual stromal bed thickness there is no absolute value that guarantees that ectasia cannot occur.  This risk of postoperative ectasia may increase with decreasing stromal bed thickness and may also be influenced by other factors yet to be identified.