Diffractive Optics Demonstrate Superiority to Enhanced Depth-of-Focus Designs in Intraocular Lenses

Two intraocular lenses (IOLs) with novel, wavefront-shaped enhanced depth-of-focus (EDoF) designs failed to outperform an IOL utilizing diffractive optics with respect to modulator transfer function (MTF), according to research published in Optometry and Vision Science.

Researchers compared 3 IOLs, 2 using the EDoF design and 1 with diffractive optics. They used an imaging test bench and emanated light at a 546 nm wavelength. The team utilized an in-situ eye model with ISO-2 corneas (n=1337) and used 2 apertures of different diameters to simulate mesopic and photopic pupils (3.0 and 4.5 mm, respectively). They compared modulation transfer function (MTF), Strehl ratio, and United States Air Force (USAF) resolution test chart images between the IOLs.

All IOLs had a nominal power of 22 D with 6 mm optics. They were made of a hydrophobic acrylic material and had refractive indexes ranging from 1.47 to 1.55.

According to the report, the IOL with diffractive optics had the best through-frequency MTF centered under simulated mesopic conditions (MTF, 0.410 vs 0.250 and 0.257 at 50 lp/mm; P <.001) with no alterations while tilted (MTF, 0.399 at 50 lp/mm). At decentration, all three lenses performed poorly (MTF range, 0.188-0.266 at 50 lp/mm). The investigators noted similar outcomes while assessing the IOLs under simulated photopic conditions.

Strehl ratios revealed similar relationships between the 3 designs for the through-frequency MTF function. The team observed the most significant dip in decentration for the diffractive optics design at 4.5 mm (Stehl, 0.098; sag.tan; P <.001).

During the USAF analysis, the diffractive optics design had a clearly readable result with a good contrast for both aperture sizes. One of the EDoF designs experienced a loss of brightness with sharp contrast at 3 mm of aperture, and blurred with the larger aperture. The other had considerable ghosting with 3 mm of aperture and a bright, blurred image with the larger aperture.

Researchers assert that the diffractive optics outperformed the EDoF lenses in terms of modulation transfer function, but acknowledge the ability of the EDoF lenses to offer patients some benefit with respect to halo reduction. “Patients will decide if they want to opt for less halos and glare in mesopic conditions and, at the same time, accept slightly less contrast sensitivity when choosing one of these new enhanced depth-of-focus intraocular lenses,” according to the investigators.

Study limitations include the use of simulations and failure to account for near vision outcomes.

Reference

Schmid R, Luedtke H, Borkenstein AF. Enhanced depth-of-focus intraocular lenses: latest wavefront-shaped optics versus diffractive optics. Optom Vis Sci. 2022;99(4):335-341. doi:10.1097/OPX.0000000000001894