*3.2.1.2.1 Apodized diffractive IOLs*

The characteristic of apodized diffractive IOLs is a decrease in height from the taller central to the shorter peripheral steps of the optic [59]. The lower steps of the periphery send more energy to the far and less to the near focal point. On the contrary, the higher central steps send equal energy to distance and near [64]. The clinical significance of this phenomenon is shown by the fact that the larger pupil diameter in scotopic light conditions, when only the distance vision is utilized, allows more energy to be directed to the distance focal point, while the smaller pupil diameter in photopic conditions, when both distance and near vision are utilized, allows energy to be directed equally to distance and near (**Figure 4**) [60, 64]. Additionally, apodized diffractive IOLs produce fewer optic phenomena (eg. glare, halos etc) than non-apodized IOL during distance vision through a large pupil [59].

Some characteristic apodized diffractive IOL models are the following:


**Figure 3.** *Examples of diffractive multifocal IOL designs.*

#### **Figure 4.**

*Light distribution in photopic (A) and mesopic-scotopic (B) light conditions in diffractive apodized IOL designs. (A) The small pupil diameter in photopic conditions, when both distance and near vision are utilized, allows light energy to be directed equally to distance and near. (B) The wide pupil diameter in low light conditions, when only the distance vision is utilized, allows more energy to be directed to the distance focal point.*
