Chapter 13: Vector Planning for LASIK, PRK and SMILE

Vector Planning for LASIK, SMILE and PRK Ocular residual astigmatism (ORA) corneal astigmatism, refractive cylinder Let’s discuss the corneal refractive differences that are often seen in refractive laser surgery and how one can address those differences to optimize the surgical outcome. Well the differences between the corneal and refractive values are prevalent and the more the differences the more possibility of an adverse outcome. So these need to be addressed. Up until now the treatment is at one extreme or another. You either treat by manifest refraction, , or you go to the other extreme and you go for a spherical cornea treating by corneal values alone, but in each of those two cases you are actually not really taking any notice of what is happening at the other level. So what can be done using the technique of vector planning is is to use both the refractive and corneal astigmatism in the treatment para So the idea of treating by a wavefront refraction really is 100% refraction. Or topographically guided is the other extreme that you mentioned, but somewhere in the middle of the of the group is the sweet spot. Yes, so all those different sophistications of wavefront refraction, corneal wavefront. The wavefront refraction is just another refractive element that does not really address the corneal values. Corneal wavefront does not address the refractive values. They are just very fancy ways of looking either at a refraction or topography, but they don’t actually incorporate the two together, which vector planning does. What’s the paradigm behind the vector planning process? Well it is quite simple actually and that is that you have to think about the target astigmatism. With the rule astigmatism is generally more optically favourable than against the rule astigmatism. and an oblique astigmatism really has no particular advantage at all. So when the target is found to be somewhere closer to with the rule, then you might swing a little bit closer to emphasising refraction because it is a favourable outcome. But if the target is unfavourable, either against the rule or oblique, then you might say I don’t really want to leave that kind of astigmatism behind on the cornea, I would rather sphericise the cornea and therefore you might give more emphasis to corneal parameters than refractive. Can Vector Planning be used for all LASIK patients? I use Vector Planning for all patients who require astigmatic treatment. The higher the ocular residual astigmatism the more important Vector Planning becomes to minimise the amount of corneal astigmatism remaining postoperatively and hence optimise visual outcomes.