EyeWorld India June 2015 Issue

38 EWAP CATARACT/IOL June 2015 Views from Asia-Paci c ZHANG Hong, MD Tianjin Medical University Eye Hospital 251# Fukang RD, Tianjin, China Tel. no. +86-13902129739 +86-2223346434 tmuechong@sina.com C orneal astigmatism is one of the most common refractive errors in the human optic system. In our clinical data, a large portion of our cataract patients had signi cant pre-existing corneal astigmatism (73%≥0.5D , 41%≥1.0D, 22%≥1.5D, 5%≥2.5D, 2%≥3D, table 1). Femtosecond lasers produce corneal incisions with great predictability and stability, which can assure the consistency of the surgical induced astigmatism (SIA). SIA is an important issue that should not be ignored when a premium IOL implantation is planned. Astigmatism exceeding 0.2 D can affect the postoperative visual outcome by the choice of toric IOL and the residual astigmatism. Many factors, such as the type of keratome, the location and size of the corneal incision, the length of the tunnel and the side of the operating eye (for surgeons prefer the superior position), could affect the SIA when the corneal incision is performed manually. For patients who are willing to be spectacle-independent after cataract surgery by correcting presbyopia and corneal astigmatism, residual astigmatism over 0.75 D can negatively affect their full range visual function and result in unsatisfactory postoperative outcome. Other important factors, including an overview and comparison of various types of biometric results, stability of the SIA, the accuracy of the axis of the toric IOL alignment, the stability of the effective lens position, are also critical to assure the optimization of the postoperative refractive state. Femtosecond lasers and the VERION system are of great value to improve the accuracy of astigmatism correction. In addition, the application of intraoperative aberrometry could provide an opportunity to reassure that the most suitable IOL will be inserted. Furthermore, the postoperative neutralization of astigmatism by the femtosecond laser provides a safe, reliable and effective way to further decrease the refractive error. In case of stable irregular corneal astigmatism, the optical biometry cannot provide reliable results. I prefer to use images provided by manual keratometry, topography, and iTrace to determine the axis of the astigmatism. In most of these patients, I can nd an axis based on these corneal topographic images. Furthermore, a relatively good best-corrected visual acuity before the development of cataract also indicates good visual prognosis. Thus, a suitable toric IOL can be chosen to achieve a favorable outcome. A 72-year-old retired engineer had cataract associated with stable corneal astigmatism due to the scar at the paracentral cornea in his right eye. He had 0.8 vision 10 years ago with spectacles. The corneal topography was distorted due to the scar. However, I managed to nd a rough axis for the corneal astigmatism and decided to insert a toric T7 IOL. The patient achieved 0.6 vision after the surgery and can be corrected to 0.8 with a lower degree of astigmatism. Editors’ note: Dr. Zhang declared no relevant nancial interests. Toric - from page 37 Table 1