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Patricia Piers, Sanjeev Kasthurirangan, Basilios Sideris; Non-invasive Evaluation of Intraocular Lens Performance. Invest. Ophthalmol. Vis. Sci. 2013;54(15):843.
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Visual performance with intraocular lenses (IOLs) such as multifocals is usually evaluated through human clinical trials with surgical implantation. Development of a new type of IOL may need multiple design iterations requiring multiple clinical trials, which may prove costly and time consuming. A method is proposed to non-invasively evaluate IOLs in lieu of human clinical trials.
Photographic images of a miniature ETDRS chart in a bench-top eye model (ACE) model) that has a cornea lens with the same spherical aberration as the average human cornea were obtained for a multifocal IOL (ZM900, Abbott Medical Optics, USA) and a monofocal control lens (CeeOn, Abbott Medical Optics, USA). Images were obtained in 12-bit grayscale at different defocus levels from +0.75 to -3.50D, in 0.25D steps, by adjusting the camera position, and for two different entrance pupil diameters of the ACE model (3mm and 5mm). A central ‘S’ letter from the ETDRS chart was cropped and scaled to different sizes for visual acuity testing using Matlab (The Mathworks, USA), psychophysics toolbox and the QUEST procedure with 4-alternative forced choice. The letter was presented on a CRT monitor (NEC MultiSync FP2141SB, Mitsubishi Electronics, Illinois) through a BITS# device (Cambridge Research Systems, UK). Visual acuity testing was performed from 0D to 3D defocus (in 0.50D steps) binocularly in two observers with no prior ocular surgery and 20/20 visual acuity. The results were compared to the data from a FDA clinical trial on the two IOLs.
Visual acuity for different defocus levels of the ‘S’ letter was 20/20 at 0D for both IOLs (mean ± SD; 911A: -0.03 ± 0.0 logMAR, ZM900: 0.01 ± 0.01 logMAR) and declined with defocus for both IOLs, but returned to 20/20 at 3D with the multifocal IOL (ZM900: 0.0 ± 0.02 logMAR). The through focus visual acuities with the multifocal IOL were similar for 3mm and 5mm apertures (all differences were within 1-line or 0.1 logMAR). When compared to clinical trial data, visual acuities with the multifocal IOL were within 1-line (or 0.1 logMAR) for all defocus levels. Data on more subjects is being collected and will be presented at the meeting.
A non-invasive method for evaluating IOLs was developed that provided visual outcomes similar to a previous human clinical trial. The proposed methodology will be useful in quickly and efficiently evaluating novel IOL designs prior to large-scale clinical trials.
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