Influence of Internal Optical Astigmatism on the Correction of Myopic Astigmatism by LASIK

Abstract

Myopic LASIK is less effective in correcting astigmatism when astigmatism is mainly located at the internal optics. Topography and refractive value should be incorporated in the treatment of patients when a significant amount of internal optical astigmatism is detected preoperatively.

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.…”

“…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.…”

New method of quantifying corneal topographic astigmatism that corresponds with manifest refractive cylinder

“…If these differences are significant, this may lead to suboptimal visual outcomes. 1,2 The better the correlation between the magnitude and the orientation of the corneal astigmatism and refractive cylinder, the less astigmatism will be left remaining in the optical system of the eye as a whole after treatment.…”