There is a real advantage we have at TLC Rockville and Tysons Corner, Mclean — we have both the VISX CustomVUE and the Wavelight Allegretto lasers. It allows me to choose between the two best in our industry and optimize each and every patient based on their needs. Most other laser centers will put all their patients on one laser platform, because that is all they have. A dirty little secret is that not all patients do as well on the same laser system and there are differences in the way these lasers work that make one or the other a better choice for a particular patient. We use the Visx Custom excimer when there is significant amount of HOA (higher order aberration) present. If the total HOA RMS (root mean square–the units that we measure HOA by) is greater than .3 we favor the Wavefront guided treatment of the VISX. The wavescan device breaks down the total HOA and we look at the total as well as type of HOA. For instance if there is significant amount of negative spherical aberration, that is also an indication for us to use the VISX CustomVUe.
If the patient is having PRK, I favor the Wavelight Allegretto. The Wavelight is not Wavefront guided, but it uses wavefront principles to create a more prolate shape post op. It is called a Wavefront Optimized laser. I also like using the Allegretto for high myopes, hyperopes and patients with high cylinder. It is a faster ablation and makes higher rx patients easier to treat without worrying about corneal dehydration during surgery and possible secondary refractive effects from that. It is also quieter, so it is nicer for jumpy patients!
PRK is of course indicated when the corneal thickness is below average. It is also indicated when there is EBMD present on the corneal surface or the Pentacams show mild irregularities such that a corneal flap may create a destabilizing effect. PRK is viewed as safer in these cases as it is less likely to create changes in corneal biomechanics which could lead to corneal ectasia. If significant dry eye is present and it cannot be rectified with Restasis, fish oils and punctual plugs, PRK is also a reasonable treatment as it doesn’t create secondary dry eye as LASIK can do on a temporary basis. Some occupations lend themselves to PRK, such as law enforcement or contact sports, martial arts, etc.. This is simply because there is a theoretical risk of flap dislocation upon a blow to the eye, (however Intralase based flaps, the kind we create, have been proven to be quite stable and tightly bound in the corneal bed. NASA and the military have approved LASIK if Intralase is used for their personnel).