We present a patient scheduled for LASIK enhancement based on conventional residual stromal thickness (RST) prediction methods in whom direct measurement of the RST changed the management due to an unexpectedly low RST. The preoperative refraction was -6.00 -0.50 x 115 in the right eye and -6.00 -0.50 x 20 in the left eye. At 9 months, the refractions had regressed to -0.50 -0.50 x 150 and -0.75 -0.25 x 145, respectively. Predicted RST based on preoperative parameters was 283 microm in the right eye and 281 microm in the left eye, sufficient for the planned enhancement. Using the Artemis 3-dimensional very high-frequency digital ultrasound arc scanner, the minimum RST was directly measured as 277 microm in the right eye but only 212 microm in the left eye, which may have significantly increased the risk of iatrogenic ectasia yielding a predicted post-enhancement RST of 253 microm and 192 microm, respectively. The treatment plan was altered as a result of the thinner than predicted RST in the left eye; an enhancement was performed in the right eye only. A second Artemis examination after 22 months found the RST in the left eye to be stable.