In this experimental study, we showed that the Proming IOL provides good MTF performance, which is close to that of its counterpart lens for a small (3.0mm) aperture size. However, at the increased aperture (4.5mm), differences became apparent between the studied designs. Furthermore, the two IOL models differ in the defocus (visual) range in which they provide satisfactory image quality. To the best of the authors’ knowledge, this is the first laboratory study characterizing the optical performance of the Proming IOL.
The Proming IOL’s MTF values at the primary focus were only minimally lower than those of the AT LARA for the 3.0mm pupil (Fig. 2, Table 1). However, when the aperture size increased, the AT LARA outperformed the Proming lens (Fig. 2, Table 2), which results from differences in the amount of spherical aberration induced by each model. This impact of spherical aberration on image and visual quality has been reported by many researchers23–25. Note that the AT LARA features an aberration-neutral design. As we used the model cornea that is also aberration-neutral, the AT LARA’s performance, ideally, would not be affected by spherical-aberration, resulting in excellent image quality. By contrast, if an aberration-correcting design were studied with an aberration-free cornea, its image quality may be degraded due to increased negative spherical-aberration. One may wonder whether the match of the model cornea and the Proming IOL caused its decreased optical performance at the 4.5mm aperture. In this study, we analyzed the optical quality using a model cornea that complements the design of the AT LARA. The Proming’s manufacturer has not disclosed the level of spherical aberration. Thus, we could not match a model cornea for its asphericity, nor the reasons for Proming’s poor imaging quality at scotopic pupil could be discussed.
To this date, two laboratory studies characterized the optical performance of the AT LARA IOL16,17. We previously measured the lens using an aberrated model cornea (+ 0.28µm) and also observed good image quality from its primary through secondary foci at 3 mm, but it was reduced at 4.5 mm17. Furthermore, we found that at primary focus, the AT LARA showed slight deterioration in its optical quality when measured with polychromatic than with monochromatic light. Yet, the difference was less pronounced than in a refractive EDOF lens, as the AT LARA employs chromatic aberration correction17. In another study, we evaluated the influence of longitudinal chromatic aberration (LCA) on the polychromatic optical quality of different multifocal lenses. We found that the AT LARA lens is able to compensate for the chromatic aberration better than other diffractive IOLs, with LCA of 0.78D at the primary focus. A value that is lower than that of an aphakic model eye (1.04D)16. At the secondary focus, the correction was more effective inducing only 0.21D of residual LCA, which led to a minimal change of the AT LARA’s optical quality compared to a single-wavelength measurement. The polychromatic MTF at 50 lp/mm was 0.30 and 0.23 at the far and intermediate focus, respectively17. While we used monochromatic conditions in this study, our results may correspond with those obtained in polychromatic light due to the low chromatic effects of the AT LARA.
The AT LARA has also been studied clinically9. In a recent paper, the visual outcomes of 11 patients with the AT LARA IOL implanted bilaterally were evaluated9. The authors found good binocular corrected distance visual acuity of -0.01logMAR and distance-corrected near visual acuity of 0.33logMAR (at 40cm) 3-months postoperatively9. It was reported that the AT LARA IOL demonstrated better performance at intermediate than at near range, with binocular distance-corrected intermediate visual acuity values of -0.07, 0.04, and 0.07logMAR at 90, 80, and 60cm, respectively9, which are in conformity with our results.
The TF MTF and the ray-visualization analysis displayed two distinct foci with the Proming IOL having the secondary MTF peak recorded at approximately 2.5D (Fig. 2, 3, and 6). Interestingly, Fig. 2 shows an extended far focus up to 1.5D, but this did not result in improved image quality at a 1-1.5D range, as one can see from the USAF resolution-chart photographs (Fig. 3). At 0.5D, however, this (far) TF MTF elongation may have led to an improvement in Proming IOL’s performance as its image quality was noticeably better than that of the AT LARA, particularly at 4.5mm (Fig. 3). However, whether patients can perceive this as an EDOF effect remains to be elucidated in a clinical study. The AT LARA also had two distinct peaks in the TF MTF scan, with the secondary peak positioned at about 1.87D (Fig. 2, 3, and 6). A relatively small separation of the AT LARA’s foci resulted in better optical quality than the Proming at the intermediate range (Fig. 3). On the other hand, the Proming provided better image quality at near (Fig. 3), which may improve patients’ reading performance.
The power measurement results indicate that the studied lenses were correctly labeled for their nominal power as the reported values were within an ISO tolerance limit of ± 0.4D20. Furthermore, the low standard deviation of the measured nominal power and minimal variability of the optical quality parameters suggest there is good reliability in the IOL’s manufacturing process.
In conclusion, the new Proming IOL showed good image quality and behaved almost as a low-add bifocal lens from the optical point of view; however, its optical properties did not differ much from the well-established EDOF IOL. At the far focus, the MTF was as good as that of the AT LARA in the presence of low spherical aberration at 3.0mm pupil. Although the AT LARA provided better MTF performance than the Proming IOL at low defocus (up to 2D), the latter demonstrated better image quality in the 2-3D range. The ray visualization and the TF MTF data confirmed an enhanced range of vision produced by the studied IOLs.