How to Perform Your Own Corneal and Refractive Vector Analyses

One of the most common questions that a refractive surgeon will want to answer is whether the procedure successfully addresses, not only the refractive astigmatism, but the corneal astigmatism as well. The analyses that should be performed are a comparison between the intended change in refractive cylinder and the actual effect of the surgery on the refractive cylinder and the intended change in corneal astigmatism and the actual change. 1 In most cases of excimer laser surgery, the intended change in astigmatism is quantified by the target induced astigmatism vector (TIA) by refraction, and the actual astigmatic effect is quantified by the surgically induced astigmatism vector (SIA) by refraction and by corneal astigmatism. The difference vector (DV) by refraction and by corneal values is the amount that the actual effect of the surgery missed the intended refractive cylindrical or corneal target.