amounts of corneal astigmatism have traditionally been addressed through peripheral corneal relaxing incisions or by judicious selection of incision site [16, 43]. However, these methods can be unpredictable, and in the case of corneal relaxing incision, involve additional incisions with the associated side effects and risks. Excimer laser surgery after cataract surgery has also been advocated to correct the astigmatism. However, this again involves an additional procedure with its associate potential side effects and risks.

The introduction of the toric intraocular lens is an obvious solution to this problem. The pre-existing astigmatism can be corrected at the time of IOL implantation with an appropriate toric IOL. This means that the patient will not have to undergo additional procedures and be exposed to the risks of the procedures. Furthermore, toric IOLs will be able to correct higher degrees of astigmatism compared to peripheral corneal relaxing incisions [27, 60]. This will enable refractive surgeon to achieve the aims of minimal invasive surgery in correcting astigmatism during cataract surgery.

5.5.2.3ACRI.LISA 366D and ACRI.LISA TORIC 466TD

Lens Design

The ACRI.LISA 366D IOL (Carl Zeiss Meditec AG, Jena, Germany) was specifically designed for MICS and can be implanted through an incision of less than 1.7 mm. It incorporates a new concept, refractive– diffractive optics, into its design to provide simultaneous good distance and near vision and to improve intermediate vision over previous designs.

The ACRI.LISA 366D is a bifocal, biconvex, optimised aspheric single piece IOL with a square-edged optic and haptic (Fig. 5.18). It is made of foldable acrylate with 25% water content which is able to absorb ultraviolet light (Acri.Lyc material) and has a hydrophobic surface. The aspheric profile of the IOL is aimed to correct the positive spherical aberration of the cornea. The sharp square edges of the IOL are designed to reduce the incidence of posterior opacification. It has an optic diameter of 6.0 mm, with an overall size of 11.0 mm.

The refractive–diffractive optics splits incident light into refractive distance focus with 65% light intensity and a diffractive near focus with 35% light intensity. The

Fig. 5.18 The ACRI.LISA 366D intraocular lens

IOL power varies from 0.00 D to +32.00 D (0.00 D to +10.0 D in 1.0 increment and +10.0 D to +32.0 D in 0.5 D increment) and incorporates a +3.75 D near addition which corresponds to +3.75 D in the spectacle plane.

The ACRI.LISA TORIC 466TD (Carl Zeiss Meditec AG, Jena, Germany) has a similar design and is composed of the same material as the ACRI.LISA 366D. However, it has an aspheric, toric anterior surface in addition to its bifocal, diffractive, aspheric posterior surface. The IOL power available is able to provide −10.0 D to +32.0 D of spherical correction and +1.0 D to +12.0 D of cylindrical correction.

5.5.2.4 Surgical Technique

Operative Procedure

Topical anaesthesia (preservative-free lidocaine 2%) and mild sedation with midazolam is used in our centre.

The clear cornea incision is placed on the axis of the positive corneal meridian, which was previously marked at the slit lamp to prevent cyclorotation, using an Alio MICS diamond blade (Katena, Denville, NJ). A second similar clear corneal incision is made 90° apart and dilation is obtained with intracameral mydriatics using 1 mL of a vial containing cyclopentolate 1% (1 mL), phenylephrine 10% (1.5 mL), lignocaine 2% (5 mL), and balanced salt solution (BSS) (10 mL). A dispersive ophthalmic viscoelastic (Viscoat, AlconCusi) is injected to fill the anterior chamber and to protect the anterior chamber structures and the corneal endothelium. Subsequently, a cohesive ophthalmic viscoelastic (Celoftal, Alcon Cusi) is injected in the anterior chamber. Capsulorrhexis is performed with an Alio MICS