Opacification Rates with AcrySof and PhacoFlex IOLs (2003)

Halpern et al.1 presented a retrospective examination of second-generation silicone (PhacoFlex® II, Allergan) and 3-piece hydrophobic acrylic (AcrySof®, Alcon) intraocular lenses (IOLs) that reports a statistically significant decrease in the neodymium:YAG (Nd:YAG) laser capsulotomy rate with 3-piece AcrySof IOLs compared with PhacoFlex II IOLs. Furthermore, they state that since the AcrySof was used in more challenging eyes, they expected that these patients would be more likely to develop posterior capsule opacification (PCO), although the opposite was observed. Posterior capsule opacification studies can be difficult under the best of circumstances, and there are complex additional problems involved in retrospective studies. There are several issues that the authors have not taken into consideration in their study and conclusions: 1. Clearly, the patients with the AcrySof IOLs were statistically significantly older; and the AcrySof IOLs were more frequently used in a morbid state. The assumption that this somehow would increase the PCO does not meet with the known facts. It is well known that the older the population, the less likely PCO will occur. In terms of compromised eyes, in at least 1 study, diabetic patients were shown to have decreased PCO as well.2 With such differences, the groups are not comparable. Therefore, drawing conclusions about PCO is problematic. 2. The difference in Nd:YAG laser capsulotomy rates and reported PCO is certainly impressive between the 2 groups, and it is therefore interesting that the visual acuity decline from 1 month to the last visit was not statistically different between the groups. Typically, PCO correlates with decreased visual acuity (which the study did show for PCO in generally but not between IOLs), and this is another reason to suggest the 2 groups were clinically different. 3. It is stated that 1 surgeon performed most of the MA30/60 IOL implantations. Surgeon technique is an extremely important factor affecting PCO. For example, in a recent study by us, a 360-degree overlap of the anterior capsule and the IOL is closely associated with decreased PCO.3 This variable alone can explain differences in PCO levels between studies and groups. Thus, lack of randomization of the surgeon is another confounding variable in the current study. 4. Patients in the PhacoFlex II group had significantly longer mean follow-up times than those in the AcrySof group. It is certainly well known that PCO increases with time; therefore, this would be another significant bias against the PhacoFlex II group and another indication that this is not an appropriate comparison of the 2 IOL types. 5. Indications among surgeons for Nd:YAG laser capsulotomy can be quite individual. This makes the capsulotomy rate a relatively weak indication of PCO. Masked prospective retroillumination analysis or other objective measurement of PCO is more reliable, especially when surgeons are not randomized. In long-term randomized clinical trials, the results have shown little or no difference between the PhacoFlex II and the AcrySof in PCO formation.4,5 Our 3-year study using masked retroillumination analysis showed no difference in PCO or rates of Nd:YAG laser capsulotomy.3 We also showed that the presence of a 360-degree overlap of the edge of the anterior capsule with the IOL is highly variable among surgeons and that this variability explains a great deal of the variability in reports of PCO. Overall, the truncated edge of the AcrySof, which easily produces a discontinuous bend in the capsule, particularly if there is a 360-degree anterior capsule overlap, seems to provide an advantage in PCO prevention. However, a recent prospective randomized study comparing the AcrySof with a square-edged silicone IOL showed no long-term difference in PCO between the 2 IOLs.6 We believe there is good evidence that if there is a difference between the AcrySof and PhacoFlex II IOLs in regard to the PCO rate, a truncated edge such as that on the new ClariFlexB IOL will eliminate this difference. We have undertaken a long-term prospective study to confirm this conclusion. Randall J. Olson MD Salt Lake City, Utah, USA