Introduction:  Intraocular lenses (IOLs) with square optic edges were associated with lower rates of posterior capsule opacification. We evaluated the microstructure of the edges of currently available hydrophobic and hydrophilic IOLs, in terms of their deviation from an “ideal” square

Materials and Methods:  Ten designs of hydrophobic acrylic, 6 designs of silicone, and 24 designs of hydrophilic acrylic IOLs were used in this study. For each design, a +20 D IOL and a +0 D IOL (or the lowest available plus dioptric power) were evaluated whenever possible. The IOL edge was imaged under high magnification scanning electron microscopy (SEM) using a standardized technique. Low vacuum (0.7 Torr) and an environmental SEM was used for the hydrophilic lenses. The photographs were then imported to a digital computer program (AutoCAD LT 2000 system, Autodesk, San Rafael, CA, USA), and the area above the posterior-lateral edge, representing the deviation from a perfect square was measured in square microns.

Results:  There was a large variation of the area values measured in currently available IOLs labeled as square edged lenses. The mean values for hydrophobic acrylic (N=19) and silicone (N=11) lenses were 183.38 +/–82.18, and 74.39 +/–88.54 square microns, respectively (all dioptric powers evaluated included). The area measurement values of hydrophilic acrylic lenses, as a group, were higher than the values reported for hydrophobic acrylic or silicone lenses (331.39 +/–218.90 square microns; N=47 lenses).

Discussion:  Analysis of the microstructure of the optic edge of currently available square edged IOLs revealed a large variation of the deviation area from a perfect square.

Conclusion:  As a group, hydrophilic acrylic lenses were found to have less square edges than hydrophobic acrylic and silicone lenses.