DEC 19, 2014
This retrospective study found that the magnitude of ocular residual astigmatism (ORA) does not seem to predict the efficacy and safety of myopic LASIK using a solid-state laser platform. The results indicate that the greater relevance of posterior corneal astigmatism after surgery in some cases may explain the presence of unexpected astigmatic residual refractive errors.
The authors evaluated the influence of the difference between preoperative corneal and refractive astigmatism, or ORA, on LASIK outcomes in 55 consecutive patients (101 eyes) with myopia or myopic astigmatism who underwent LASIK surgery using the Pulzar Z1 solid-state laser.
At six months’ postop, uncorrected distance visual acuity had improved significantly (P < 0.01) from before surgery, and refractive cylinder magnitude and spherical equivalent were reduced significantly (P < 0.01). In contrast, there were no significant changes in ORA magnitude or anterior corneal astigmatism.
The mean overall efficacy and safety indices were 0.96 and 1.01, respectively, which were each not correlated with preoperative ORA. Furthermore, there was a significant correlation between ORA and posterior corneal astigmatism postoperatively but not preoperatively. Likewise, ORA and manifest refraction were significantly correlated only postoperatively.
They write that the potentially higher contribution after surgery of posterior corneal astigmatism to ORA and consequently to the total refractive astigmatism seems to be a crucial factor for the presence of unexpected astigmatic residual refractive errors after LASIK with a solid-state laser.
They conclude that caution should be taken with LASIK cases presenting preoperatively with relatively high posterior corneal astigmatism because its effect on postoperative refractive cylinder can become clinically very relevant. In such cases, an appropriate vector analysis would allow the surgeon to define a more precise surgical plan.