Purpose:
To evaluate the astigmatic orientation in refractive patients as related to the benefits of oval LASIK flaps.
Methods:
A retrospective data base analysis was performed on the refractive evaluations of the surgery patients that were evaluated at TLC The Laser Eye Centers from January 2000 to December 2009 (84,271 eyes). Patient ages ranged from 18 to 70 years of age. The refractive error orientation was divided into three groups; with-the-rule (WTR) with the negative axis at 180 + 15, against-the-rule (ATR) with the negative axis at 90 + 15 with the intervening axes considered oblique.
Results:
The incidence of WTR, ATR, and oblique astigmatism rose from 0.76%, 1.13%, 0.71% respectively in eyes with a spherical equivalent (SE) ≤1 diopter (D) to an incidence of 49.26%, 19.93%, 28.83% in eyes with a SE of ≤10D. The incidence of WTR, ATR, and oblique astigmatism rose from 15.09%, 6.81%, 11.48% in eyes with ≤ 1D of astigmatism to an incidence of 50.33%, 20.30%, 29.66% in eyes with ≤ 5D of astigmatism. Overall, 77.3% of eyes had an astigmatic orientation (42.4% WTR, 36.9% oblique) that results in a horizontal oval ablation treatment pattern.
Conclusions:
The majority of myopic astigmatic refractive patients have either WTR or oblique astigmatism. This results in an oval horizontal corrective ablation pattern that can be symmetrically applied to an oval horizontal corneal flap bed.
Keywords: refractive surgery: LASIK • astigmatism