JUL 26, 2011
This letter challenges the results reported in a letter published in the Journal of Cataract & Refractive Surgery in 2010 that suggest that IOL power needs to be increased when implanted in the ciliary sulcus as opposed to the capsular bag to achieve the same refractive result. Data analysis performed by the authors of the current letter suggests that a greater reduction in IOL power is required when a higher power IOL is placed in the ciliary sulcus than in the capsular bag.
Given that the IOL power reduction for sulcus placement was slightly less than that predicted by theoretical calculations and because postoperative myopia is preferable to hyperopia, the authors suggest reducing the bag power by 5 percent (1/20) when implanting in the sulcus. This allows the adjustment to be proportionate to the IOL power rather than the usual 0.5 D adjustment across the board that most surgeons make. However, this could be splitting hairs, since most manufacturers only give us 0.5 D IOL steps to choose between.
The authors used an electronic database to identify patients who had undergone sutureless phacoemulsification and sulcus IOL implantation with or without automated anterior vitrectomy but without other procedures. The IOL power that would have predicted the actual postoperative refraction if implanted in the capsular bag was calculated for the Holladay 1 formula and the SRK/T formula for each eye using optimized formula constants. The relationships between IOL power reduction and capsular bag IOL power and axial length were determined by linear regression using R 2.10.1 statistical software (R Foundation for Statistical Computing).
IOLs had been placed in the ciliary sulcus in 170 (0.1 percent) of the 14,193 consecutive eyes that had undergone phacoemulsification. Twenty-four of these eyes met the inclusion criteria for this analysis; all of them received the LI61AO Sofport IOL (Bausch & Lomb). The mean IOL power reduction for sulcus implantation was -0.66 D (standard deviation 0.67 D). For both formulas, the IOL power required for ciliary sulcus placement was 96 percent of that required for capsular bag placement (both R2 > 0.64, P < 0.05), equivalent to reductions of between 0.625 D and 1.25 D for capsular bag IOL powers between 15.0 D and 30.0 D. The correlation between axial length and IOL power reduction was not significant (both R2 = 0.11, P < 0.05), but there was a trend toward greater reduction being required as axial length decreased.