Geometry of Modern Presbyopia-Correcting Intraocular Lenses and Changes in Haptic-Capsular Bag Behavior According to Compression and Different Well Diameters: A Bench Study Using Computed Tomography.

INTRODUCTION

The geometry of an intraocular lens (IOL), the design of the haptics, and the optic-haptic junction play a role in initial and long-term visual outcome after cataract surgery. Knowledge of the behavior of an implant in the capsular bag and under compression is of major importance. Our laboratory experiment analyzed in-depth the geometry of acrylic, single-piece, premium, presbyopia-correcting intraocular lenses and changes in haptic-capsular bag relationships according to capsular bag size using a range of compression well diameters.

METHODS

One hydrophilic (RayOne Trifocal RAO603F) and three hydrophobic intraocular lenses (AcrySof IQ PanOptix, Synergy DFR00V™, and AT ELANA 841P) were scanned with computed tomography (CT) in a dry, uncompressed state for quantitative analyses of haptic and optic-haptic junction (OHJ) dimensions and qualitative assessment of geometry. In the second part of the experiment, CT was performed after sample placement into a series of compression wells (9.0, 10.0, 11.0, 11.5 mm) for analyses of length of contact (LoC) between the haptics and the wells. Axial alignment and haptic-capsular bag relationships were assessed.

RESULTS

The qualitative and quantitative evaluations highlighted differences in haptic and OHJ geometry and dimensions across the samples. The mid-zone of the optic was thickest in the hydrophilic sample (RayOne Trifocal RAO603F) with a maximum of 0.880 mm compared to the thinnest hydrophobic sample (AT ELANA 841P) with 0.564 mm. The AT ELANA 841P showed the largest OHJ surface area (3.86 mm) and OHJ volume (0.60 mm) of the hydrophobic samples. The TECNIS Synergy DFR00V™ showed the thickest OHJ (0.51 mm), while the AcrySof IQ PanOptix showed the thinnest OHJ (0.21 mm). The LoC values decreased with increasing well size for all tested samples. The AT ELANA 841P showed the largest LoC and largest contact zones of hydrophobic samples in all wells.

CONCLUSION

The laboratory experiments highlight differences in the haptics, the OHJ geometric characteristics, and behavior of samples in different well diameters. The results support the idea that specific IOL designs may have advantages or disadvantages depending on anatomical dimensions. We cannot make any classification or rating (good versus bad) for clinical practice on the basis these experimental results, as many other factors play a role. However, knowledge of IOL geometry seems important to select the best option in each individual case.