Quantitative Performance of Bifocal and Multifocal Intraocular Lenses in a Model Eye

Abstract

To compare the optical properties of bifocal diffractive and multifocal refractive intraocular lenses. Methods: A model eye with a pupil 4.5 mm in diameter was used to determine the point spread function (PSF) of the distance focus and near focus of a diffractive bifocal intraocular lens (IOL) (model 811E; Pharmacia Inc, Columbus, Ohio) and of a refractive multifocal IOL (model SA40N; Allergan Optical Inc, Irvine, Calif) to compare them with PSFs of foci of corresponding monofocal lenses. For interpreting the PSFs the through focus response, the modulation transfer function, and the Strehl ratio were evaluated. Results: The intensity of the distance focus of the bifocal diffractive lens reached 58.5% and the near focus attained 42.7% of the intensity of a corresponding monofocal lens. The maximal halo intensity surrounding both

Optomechanical eye model with imaging capabilities for objective evaluation of intraocular lenses

“…Also chromatic aberration is expected to be equivalent to that of a real eye because of the similar constringence of PMMA and corneal stroma (57.2 and 56, respectively). Incidentally, the PMMA cornea of the artificial eye developed by Pieh et al, 4 exactly reproducing the curvatures of the Gullstrand eye model, has a power in defect by 4% relative to the Gullstrand power as a result of the different refractive index.…”

“…This image can then be analyzed with standard optical methods to recover PSF, MTF, or aberration coefficients for different pupil sizes, as done in other studies. 1,2,4,5,8,30 All these quantities completely characterize the linear optical behavior of the eye model, thus allowing immediate and homogeneous comparison of IOLs with equal dioptric power and different material or design features.…”

“…The only quantitative data available are in the form of modulation transfer function (MTF) plots that manufacturers sometimes include in the IOL technical data sheet, however, without uniformity of test conditions, and, moreover, without a direct link to a sound index for the quality of vision. At the same time, few reports give a comparative optical characterization of some IOLs, [1][2][3][4][5] and in a few cases they are limited to an analysis of the optical quality of the lenses. [6][7][8][9] On the other hand, many clinical studies have evaluated and compared the visual outcomes in large patient populations after lens extraction and IOL implantation.…”

New trends in intraocular lens imaging

“…In addition to this, some of these lenses have an aspheric base design that can be advantageous in comparison the conventional spherical one. There is a great interest to determine either in a test bench [43], [44] or in clinical studies [45], [46] the conditions and the degree to which the aspheric design in apodized diffractive multifocal IOLs might be advantageous versus a conventional spherical design, particularly when some studies have shown little or no benefit of aspheric IOLs with small pupils [47, [48]. For the assessment of the optical performance of multifocal IOLs, the common metrics (point spread function, modulation transfer function, and visual acuity) have to be measured [38], [49][50][51][52] and also its behaviour in terms of the energy balance between the distance an near images and its variation with the pupil diameter.…”

A novel approach to design intraocular lenses with extended depth of focus in a pseudophakic eye model

“…Negish et al [2] and Pieh et al [3] constructed an artificial eye with a man-made cornea, an IOL, a charge-coupled device (CCD) camera, and filled water to simulate aqueous and vitreous. Then the retinal image quality with a monofocal or multifocal IOL was evaluated by the images acquired with CCD camera.…”