Abstract
Purpose :
Although bifocal and trifocal diffractive intraocular lenses are effective in correcting presbyopia, the fact that retinal image quality is significantly degraded between the designed foci remains a limitation. One potential solution can be to generate more foci, resulting in improved through-focus image quality. The goal of this study is to evaluate a new method to design a quadrifocal diffractive presbyopia-correcting ophthalmic lens.
Methods :
To design a quadrifocal lens with focal points at 0, 1, 2 and 3 diopters (D), two bifocal diffractive lenses, one for 0 and 2D and the other for 1 and 3D, are radially cut into rings based on a threshold value in wavefront phase (one below and one above). The rings are combined to be a quadrifocal lens. To validate the performance of the quadrifocal lens, an optical bench testing system equipped with a spatial light modulator generating the diffractive design was constructed. The quadrifocal lens was compared against a typical trifocal diffractive design (foci at 0, 1.5 and 3D) for a 4mm pupil with 579nm monochromatic light. An image quality metric, area under modulation transfer function (areaMTF) calculated from the collected images of a letter E chart through the lens designs, was used to quantify retinal image quality at various object distances ranging from 0 to 3D.
Results :
Both simulation and bench testing showed that the quadrifocal lens created peak image quality at the designed foci. The quadrifocal design provided significantly better image quality at 1 and 2D than the trifocal design at the cost of slight image quality degradation at 0 and 3D. As expected, image quality at 1.5D was significantly better with the trifocal lens. Both diffractive designs showed similar overall through-focus image quality represented by the sum of the areaMTF values between 0 and 3D. Additional simulation demonstrated that by controlling the relative phase and ring width between the two bifocal designs, the relative image quality at the four foci could be manipulated as needed.
Conclusions :
A newly designed quadrifocal diffractive lens for presbyopia correction was proposed. The results demonstrated that generating more than 3 foci was feasible, without sacrificing overall through-focus image quality.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.