Abstract
Purpose :
Most of the current presbyopia correcting intraocular lens (IOL) designs incorporate two or three foci. This leads to a reduction in the quality of vision between two consecutive foci. One way to make this interval between the foci shorter is to increase the number of foci. Theoretically, it has been shown that a diffractive quadrifocal optical design can be created to maintain good image quality at four foci while reducing the interval between them. However, the visual performance attainable with the same design has not yet been quantified. This study aims to evaluate the visual performance of the aforementioned diffractive quadrifocal design by measuring monocular through focus visual acuity (VA) under monochromatic light.
Methods :
The quadrifocal design was created to focus at infinity along with three add powers at 1D, 2D and 3D. A spatial light modulator was used to alter the phase of the light in order to simulate the diffractive optical element. Monocular through-focus high contrast VA is measured (n=3) between optical vergence of +1D to -4D in 0.25D intervals under monochromatic light conditions with a wavelength of 550 nm. All eyes were cyclopleged and lower order aberrations were corrected using trial lenses. A 4 mm artificial pupil was used for the VA assessment.
Results :
The through-focus VA revealed four distinct peaks with the quadrifocal design. The range of visual acuities in logMAR were 0 to -0.24, -0.04 to -0.2, -0.07 to -0.21 and -0.03 to -0.20 for the add powers of 3D, 2D, 1D and at infinity respectively. An average shift of 0.27D was noticed for all the peaks.
Conclusions :
The study found that a diffractive quadrifocal design can produce clear vision at four distinct foci. Excellent VA performance achieved at the designed foci as well as between the foci, suggesting that the quadrifocal design could be a promising approach to overcoming conventional multifocal presbyopia correction methods. However, it is important to note that visual performance assessment under polychromatic light will be necessary to further characterize the quality of vision under natural viewing condition.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.