Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: Comparative study

Abstract

The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.

Ocular residual astigmatism’s effect on high myopic astigmatism LASIK surgery

“…It makes sense that, given the fact that the magnitude of the ORA seems to be similar in eyes with high myopic astigmatism than in those with low myopic astigmatism, then the ORA/ACA ratio would be higher in the latter group. This fact could explain why the preoperative ORA seems to play a significant role in the refractive outcome of eyes with low preoperative refractive astigmatism, 16,17 but seems to have a negligible effect in eyes with high preoperative astigmatism (as we found in the current paper).…”

“…We also found that the visual and refractive results obtained after performing LASIK to correct high myopic astigmatism did not seem to be affected by the magnitude of the preoperative ORA. This seems to contradict the findings of Kugler et al 16 and Qian et al, 17 who studied the effectiveness of LASIK for correcting low myopic astigmatism and found significantly better refractive results in eyes with low ORA than in eyes with high ORA.…”

“…22 The efficacy of LASIK is well established; however, it seems to be less effective for correcting astigmatism than for correcting spherical refractive errors, and some studies have reported that the presence of preoperative astigmatism increases the retreatment rate after surgery. 23,24 Some studies have suggested that the refractive results after performing LASIK in eyes with low myopic astigmatism seem to be worse in those eyes that have a significant amount of preoperative ORA, 16,17 even suggesting that when significant ORA is identified preoperatively, it might be prudent to incorporate a vector planning into the surgical plan.…”

“…In these eyes, keratometric, topographic, and refractive astigmatism are similar to each other in magnitude and axis. In contrast, the same authors 16 have reported that the efficacy of LASIK to correct low myopic astigmatism was significantly lower in eyes with high preoperative ORA (defined as ORA/RZ1, R being the preoperative refractive astigmatism). A possible explanation for this might be that in eyes with high ORA LASIK must create a toric cornea to compensate for ORA, which can affect the postoperative visual results.…”

“…Renewed interest is being expressed in ORA, because recent studies 16,17 suggest that LASIK correction of low myopic refractive astigmatism has a better refractive outcome if the preoperative refractive astigmatism arises primarily from the anterior corneal surface. In these eyes, keratometric, topographic, and refractive astigmatism are similar to each other in magnitude and axis.…”