Eyeworld

by John Berdahl, MD Succeeding with toric IOLs Toric Results Analyzer (astigmatism- fix.com), which David Hardten, MD, and I developed. This free tool helps surgeons determine whether rotating the IOL will correct the problem. The IOL had rotated approx- imately 30 degrees from where I intended to place it. I performed intraoperative wavefront aberrometry. We rotated the IOL 28 degrees, as recommended by the astigmatismfix.com calcula- tor. It was only one week after the initial surgery, so the haptics had not fused into the posterior capsule. We need to be sure the haptics are freed from the sulcus of the capsule. I placed viscoelastic on top of the IOL to loosen it, and after rotating the IOL, I removed the viscoelastic. When we repeated intraop- erative aberrometry, astigmatism decreased from 3.15 to 0.43 D. The next day, the patient's visual acuity was 20/20 and she was pleased with her vision (Figure 1). Targeting the root cause There are a number of potential reasons for residual astigmatism after implantation of a toric IOL, including ocular surface disease, an- terior basement membrane disease, or irregular astigmatism. We need to treat disease that is present and, ideally, not place the lens in such an eye. Minimizing residual astigmatism is critical to obtaining optimal results with premium intraocular lenses P remium intraocular lenses (IOLs) enable us to offer a range of options to fit our patients' lifestyles, and toric IOLs are an excellent way to enter the premium IOL field. However, to achieve optimal out- comes that will meet patients' needs, it is important to know how to pre- vent postoperative residual astigma- tism and correct it if it occurs. Case report A patient had 3.5 D of astigmatism one week after implantation of an Acrysof Toric T9 IOL. The surgery corrected approximately 0.5 D of her 4.0 D of astigmatism—not the expected correction for this reliable toric lens. I entered her manifest reaction, toric IOL, and current axis into the Figure 1. Before (left) (–1.75 + 3.50 x 92; VAsc 20/70) and after (right) (plano; VAsc 20/20) rotation of a toric T9 IOL The IOL may be in the incorrect location or we may have used the wrong lens power because preop measurements and calculations were inaccurate. We also need to account for cyclorotation, performing pre- operative marking with the patient in the upright position. A surprising surgically induced astigmatism or posterior corneal curvature is often the cause of residual astigmatism. I perform a topography mea- surement and use it to determine the axis in my calculator. Then I use the Ks from LENSTAR or IOLMaster to determine the magnitude of the astigmatism. We need to be sure the Ks from different sources are consistent. Finally, the IOL may have ro- tated or been placed incorrectly. For every degree the lens is misaligned, we lose 3.3% of the toric IOL power (Figure 2). Intraoperative aberrome- try is important, and I recommend considering intraoperative align- ment technologies. From our website, we have found that preoperative biometry was not adequate in 76% of cases of residual astigmatism. In addition, 70% of the time the IOL rotated and in 52% of cases, residual astigmatism resulted from a combination of the two. Surgeons also need to know their surgically induced astigmatism and how it affects the axis. In addi- tion, in approximately 80% of cases there is against-the-rule astigmatism on the posterior cornea, and in roughly 15% of cases with-the-rule astigmatism is present. " It is important to know how to prevent postoperative residual astigmatism and correct it if it occurs. " –John Berdahl, MD continued on page 134 132 Crossing the finish line: Launching your premium technology practice John Berdahl, MD

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