Evaluation of Depth of Focus of IOL Designs
Narrative Responses:
Purpose
In this study we investigate the depth of focus (DOF) of intraocular lens designs using innovative methodologies.
Methods
DOF was assessed for monofocal, multifocal, and trifocal lenses. Throughfocus image quality was evaluated with optical bench testing in white light. The optical bench consisted of a model eye, comprising a glass cornea, wet cell, and a camera for imaging. The cornea had the spherical aberration and chromatic aberration of an average cataract patient. The focal position was varied in steps of 0.125 diopters. Images of the US Air Force target were recorded, and the modulation transfer function was measured. In addition, the influence of pupil size was demonstrated. For some designs, simulated defocus curves were obtained from computer simulations.
Results
The optical bench tests show large differences between different multifocal and trifocal designs. Increasing the pupil from 3.0mm to 5.0mm reduced the near MTF by 0% to 65%, depending on lens design. For the trifocal IOLs, the intermediate MTF decreased about 40% when the pupil is increased from 3.0mm to 5.0mm. All, except the Tecnis multifocal designs, show a pupil dependent behavior. The optical bench tests show a low image quality at intermediate distances. This is not in accordance with clinical experience. The difference between the bench tests and clinical experience is explained by the computer simulations.
Conclusion
Different evaluation techniques were used to assess DOF. Each method has its own characteristics. The results show that the performance of almost all IOL designs is dependent on pupil size. The Tecnis multifocal IOL was the only tested lens that has a performance that is independent of pupil size.