**Acknowledgements**

*Visual Impairment and Blindness - What We Know and What We Have to Know*

*Image simulation for 4.5 mm of pupil in distance vision (top) and near vision (bottom) for the three Cis in the two model eyes. The intensity of the image simulation of SACI in near vision has been multiplied 4×.*

and definition. The reason that they resemble for distance vision is because with a large pupil, a part of the light that passes outside the inlays (external diameter of 4.15 mm) goes to the far focus. Therefore, the intensity ratio between the far and

By comparing both pupils, the best foci in the distance are for the DCIs with 4.5-mm pupil. The best focus for near vision is the DCI 1.0 since it presents more

We have demonstrated that both DCI designs have a clearly bifocal profile due to their diffractive nature. Moreover, they also have better MTFs and AMTFs than the SACI (see **Figures 3** and **4**). The results presented in this chapter confirm the versatility of the DCI design because, opposite at what happens for the SACI which only presents a fixed depth focus, the distribution of the holes in the DCI can be modified (customized) to alter the relationship between the far- and near-vision foci. It is also verified that while for the 3.0-mm pupil, the three CIs have a similar behavior in both eye models, for 4.5 mm the differences are more due to the high-

The PSFs show the differences between each CI for each situation; on the one hand, the DCIs generally show higher peaks and a high energy concentration and less extension of the PSF, but higher than SACI. These results can be clearly appreci-

In summary, the DCI is a diffractive CI that combines the principle of operation of the small-aperture inlay, for the central hole, with the diffraction generated by the micro-holes in the ring to generate a focus in near vision. The micro-holes allow the construction of a single-piece inlay able to be inserted into the corneal stroma allowing nutrients to pass through it. The results show that the light throughput of

near foci increases and is similar for both DCIs.

diffractive rings contributing to the near focus.

**52**

**Figure 8.**

**6. Conclusions**

order aberrations of each model.

ated in the simulated images shown in **Figures 7** and **8**.

*Funding*: Ministerio de Economía y Competitividad (DPI2015-71256-R); Generalitat Valenciana (PROMETEO/2019/048).

D. Montagud-Martínez and V. Ferrando acknowledge the financial support from the Universitat Politècnica de València, Spain (fellowships FPI-2016 and PAID-10- 18, respectively).

D. Montagud-Martínez acknowledges the financial support from the Universitat Politècnica de València, Spain (fellowship FPI-2016).

## **Conflict of interest**

The authors declare no conflict of interest.
