MILAN — As surgeons are using toric IOLs more frequently, it is important to optimize their potential, according to a specialist here.
Jay S. Pepose
Dry eye and ocular surface disease should be identified and treated, as they can impact fidelity of measurements. Optimizing incision and incision location to minimize surgically induced astigmatism (SIA) is another important step, he said.
“SIA is generally higher with superior and nasal corneal incisions vs. temporal or superotemporal. Recent studies also indicated that wound length impacts corneal biomechanics and, consequently, on SIA,” Pepose said.
Finally, look for irregular astigmatism and beware of forme fruste keratoconus, Pepose warned.
“If the manifest axis does not align with the keratometric axis, better not implant a toric lens. These patients are likely to continue to need rigid contact lenses to see well after surgery, and this will unmask the toricity of the IOL,” he said.
Posterior corneal astigmatism should also be taken into account to avoid estimation errors in terms of magnitude and axis.
“For every degree we are off-axis we are going to have a 3.3% reduction in the impact of the IOL. With 10°, we have lost a third of the effect of the IOL,” Pepose said.
Measurement of posterior astigmatism can be performed directly with tomography or indirectly with intraoperative aberrometry. New ray tracing formulas have shown efficacy in achieving ± 0.5 D in more than 83% of the eyes, he said.
Disclosure: Pepose is a consultant to AcuFocus, Bausch + Lomb, Clarity Medical, Mimetogen, Seven Sights, TearLab, TruVision, and Versant.