Advances in Cataract Surgery

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Advances in Cataract Surgery

Toric IOL


The first toric IOL available in the US market was the STAAR toric IOL (STAAR Surgical Co, Monrovia, CA, USA). The first version of STAAR toric IOL was approved by the FDA in 1998. The overall haptic diameter was 10.8 mm. The STAAR toric IOL suffered from early postoperative rotational instability, particularly when implanted in large myopic eyes. The newer version has longer haptic length (11.2 mm) and has been shown to be more stable than the older version. However, widespread acceptance and usage was limited. The STAAR toric power at the IOL plane for both models is 2 and 3.5 D, corresponding to 1.4 and 2.3 D at the corneal plane.

In 2005, the one-piece acrylic Acrysof Toric IOL (Alcon Laboratories Inc., Fort Worth, TX, USA) was granted approval by the FDA. The lens has excellent rotational stability, with less than 4° of rotation at 1 year. Poll et al., showed that eyes with astigmatism ≥2.26 D that were implanted with a toric lens implant were more likely to achieve 20/40 UDVA compared to PCRIs.

Subsequent Acrysof Toric lenses can correct up to 4.11 D of astigmatism at the corneal plane. Visser et al. evaluated the effectiveness of Acrysof Toric SN6AT6 to SN6AT9 model IOLs to correct cylinder powers ranges from 2.50 to 4.50 D. They found that these IOLs were safe and effective at correcting astigmatism in eyes with >2.25 D of corneal astigmatism. The use of toric IOLs is controversial in eyes with irregular astigmatism, higher order aberrations, or zonular weakness. Postoperative IOL rotation significantly decreases the effectiveness of toric IOLs. There is a 3.3% loss of astigmatic correction for every 1° of off-axis rotation. Patients with long axial lengths have a higher risk of postoperative toric lens rotation.

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