Diffractive Trifocal and Refractive Bifocal IOLs Similarly Effective in Axial Myopia

Both diffractive trifocal and refractive bifocal intraocular lenses (IOLs) have efficacy, accuracy, and predictability in eyes with axial myopia, according to a prospective cohort study published in BMC Ophthalmology.

The researchers included 80 patients (44 women; mean age, 68.9±10.6 years) who underwent unilateral cataract surgery with either a diffractive trifocal IOL or a refractive rotationally asymmetric bifocal IOL between 2017 and 2020 at the Peking University Third Hospital in China. Outcomes of diffractive trifocal and reactive bifocal IOLs were evaluated among patients with axial myopia, defined as an axial length (AL) longer than 24.00 mm, and controls, defined as an AL of 24.00 mm or shorter.

At baseline, control and myopic eyes had significantly different spherical equivalents (mean range, -0.87 to -0.30 vs -3.86 to -3.21 D; P <.001), anterior chamber depths (mean range, 2.93-2.95 vs 3.21-3.25 mm; P =.009), and pupil diameters (mean range, 2.79-2.94 vs 3.27-3.31 mm; P =.035), respectively. The control and axial myopic eyes received IOLs with differing power (mean range, 20.40-21.23 vs 15.34-15.90 D; P <.001) and the trifocal and bifocal IOL groups differed for target spherical equivalents (mean range, -0.15 to -0.13 vs 0.11-0.12 D; P <.001), respectively.

At 3 months post-implantation, corrected distance visual acuity of the myopic (mean, 0.31 logMAR; P =.007) and control (mean, 0.32 logMAR; P =.043) trifocal IOL recipients was superior to bifocal IOL recipients with axial myopia (mean, 0.37 logMAR).

Postoperative spherical equivalents did not differ significantly between groups (P =.0478) and the proportion of patients achieving an equivalent between -0.25 D and 0.25 D ranged between 35% (myopic trifocal) to 55% (control bifocal). The prediction error, or the difference between target and postoperative spherical error, was significantly smaller among myopic trifocal recipients compared with myopic bifocal recipients (P =.015) and among control trifocal recipients compared with control bifocal recipients (P =.027).

In general, contrast sensitivity did not differ between groups under different light conditions at different frequencies, with the exception that the myopic trifocal IOL group had better contrast sensitivity than the other 3 groups at 12 cpd under mesopic condition with glare (all P ≤.049).

Total aberrations, higher-order aberrations, coma aberrations, spherical aberrations, trefoil aberrations, modulation transfer function (MTF), and Strehl ratios differed significantly between the 4 cohorts (all P ≤.022). In general, the diffractive trifocal IOL groups had smaller aberrations and MTF and higher Strehl ratios than the refractive bifocal groups.

No postoperative complications were reported in this study.

“The diffractive trifocal IOL and the refractive rotationally asymmetric bifocal IOL both provided good efficacy, accuracy, predictability and safety for eyes with axial myopia,” according to the researchers. “By contrast, the diffractive trifocal IOL had a better performance in corrected distance visual acuity and visual quality.”

The major limitation of this study was that no long-term assessment was included.