OCT 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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Page 51 of 168

October 2012 EW CATARACT 49 visualize if it is shallow, so a scleral cutdown may be required. This can be done with a 54 Beaver blade, placing a 1 mm incision that begins 1 mm behind the limbus and extending posteriorly. The Kelly punch can be used to create a window after the supra- choroidal space has been accessed. More than one sclerotomy may be required in some cases. To prevent a choroidal effusion, it is critical to maintain a stable and deep chamber throughout the surgery. Each time that the phaco or I/A tips leave the eye, the surgeon should inject balanced salt solu- tion or OVD to maintain chamber depth. Hyperopia and lens selection Accurate biometry is especially im- portant in short eyes, as small errors in axial length have a disproportion- ately large effect on the refractive outcome. IOL power formulas are also traditionally less accurate at the extremes of axial hyperopia. Newer generation formulas, such as the Holladay IOL Consultant or Hoffer Q, may provide improved accuracy. Indicated IOL powers can range from 40-60 diopters and are often higher than available in a single lens. Our preference is to implant the highest power foldable IOL in the bag (currently 40 D in the U.S.), placing a second IOL in the sulcus. Formulas for piggyback lens calcula- tions are available. IOLs of two different materials, or two silicone IOLs, may be preferable in order to prevent interlenticular opacification. One exception is eyes with ex- tremely shallow anterior chambers pre-op and intraoperatively. In these situations, the first IOL in the bag may sit so anteriorly that a) its effec- tive power is much higher, and b) there is no space in the sulcus for the second IOL. If there is any doubt about the adequacy of the space for the second IOL, we recommend postponing its insertion. This allows one to assess both the dioptric need and anatomic feasibility of a piggyback lens. In some eyes with an extremely small anterior segment, it can be difficult to perform all aspects of the surgery, including IOL insertion. These eyes may have corneal diame- ters of 8 mm or less (our lowest is 6 mm), and complication rates of zonular dehiscence and capsular rupture are high. Extensive pre-op counseling is important. Finally, patients with high hyperopia and unilateral cataracts should be counseled that post-op anisometropia may require a contact lens or surgery in the other eye. EW References Seki M, Fukuchi T, Ueda J, Suda K, Nakatsue T, Tanaka Y, Togano T, Yamamoto S, Hara H, Abe H. Nanophthalmos: quantitative analysis of continued on page 50

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