Endothelial distance after phakic iris-fixated intraocular lens implantation: a new safety reference

PURPOSE To evaluate the distance between the endothelial surface of the cornea to the anterior edge of an Artiflex® phakic intraocular lens (IOL) implant to improve the safety profile of this implant. METHODS This is a retrospective clinical case series of 45 patients who had Artiflex phakic IOL implantation (Artiflex p-IOL) with a follow-up period of 3 years. A Pentacam HR imaging system was used to measure the distance from various points of the anterior edge of the Artiflex IOL to the endothelial surface of the cornea, which we called endothelial-IOL (E-IOL) distance, in 45 eyes. The E-IOL distances were assessed at 1, 3, 6, 12, 24, and 36 months. Corresponding correlations of central endothelial distance to temporal and nasal edges and center of the IOL anterior surface were tabulated. RESULTS Mean follow-up was 21.39±11.28 months. A statistically significant reduction of the E-IOL distance was observed over the follow-up period (P<0.05), with the mean annual reduction being 24.70 μm. A strong positive correlation between the E-IOL distance of the edges of the IOL and the central distance was observed (correlation coefficients nasal/central: month 1, 0.905; month 36, 0.806; temporal/central: month 1, 0.906; month 36, 0.806; P<0.001). Moderate negative correlations were found between the spherical equivalent power of the implanted IOL and the E-IOL distance (correlation coefficients -0.271 to -0.412, P>0.05). For an E-IOL distance of the IOL edge >1500 μm, the distance from the endothelium to the central point of the p-IOL optic should be a minimum of 1,700 μm to improve the safety profile for Artiflex p-IOL implantation and reduce the potential complication of accelerated endothelial cell loss. CONCLUSION After Artiflex IOL implantation, the mean annual reduction of the E-IOL distance was 25 μm. A negative correlation existed between the spherical equivalent power of the implanted IOL and the postoperative E-IOL distance. The minimum E-IOL distance from the center of the IOL to minimize the risk of endothelial cell loss was 1.7 mm. This distance, as is the 1.5 mm initially proposed by Baikoff, is a postoperative value. We cannot make that assumption for the preoperative evaluation, as the morphometry of the anterior chamber changes with the implant.