Fig. 8.17 Implants meant for microincision: (a) 4 rest areas: Akreos MI 60 (Bausch and Lomb), (b) 2 rest areas: Acri.Smart 48 S (ZEISS)

made up of hydrophilic acrylic material and were very thin. They did not have continuous 360° posterior barrier and included two equatorial zones (Fig. 8.17b) that made them likely to favor early postoperative capsular opacifications, excessive saccular contractions that could lead to capsulo-phimosis, or even lens subluxations. The following models have considered these weaknesses to show better mediumand long-term behavior.

8.2.3.3 Optic Design

The optic volume should be reduced in order to follow the microincision. This reduction in thickness can be obtained by various procedures like the use of a confocal optical system (ThinOptix) or by reducing the optical zone diameter. However, the diameter of the optical zone should be about 6.00 mm at +20 dpt. There is a strong desire to reduce this diameter to 5.00 mm or less in order to reduce the central thickness of the implants, and hence their volume during injection. But then there is a high risk of creating optical aberrations that annoy the patient even in case of a slight decentration.

Moreover, in case of implants with concentric confocal optics that limit their thickness, there is a possibility of patients frequently complaining about halos or glares.

8.2.3.4 Haptic Design

Haptics are used for stabilizing the optics of the IOL and avoiding any movement during the postoperative saccular contraction. However, if they are numerous and fragile, they can theoretically affect the implantation technique. Their posterior angulation can equally help in limiting the PCO by prematurely increasing the posterior capsular angulation after intervention [5]. These haptics should support 1–2.00 mm compression in the capsular sac without causing optical decentration. This is very important, as reducing the thickness of an implant – an indispensable factor for being able to insert it through a small incision – significantly modifies the stability of the implant and makes it necessary to entirely reconsider the ansae to adapt them according to this new situation. The use of large ansae, multiple to divide the efforts or even angular ones to increase the pressure on the posterior capsule and strengthen the effect of the 360° barrier, is recommended. Thus, the anterior and posterior capsules can adhere to each other earlier on all four locations (Fig. 8.16a).

Though these haptics, which are useful for the right postoperative behavior of the IOL, theoretically make the injection trickier, their specific global design and quality of injection systems do not make it so in practice.

8.2.3.5 Posterior Barrier (360°)

This barrier is mandatory even if it increases the optic thickness and therefore makes the injection more difficult.

8.2.4 Injectors Meant for Microincision

The injectors meant for microincision should have an original design in order to fulfill the requirements. Equipped with high-performance cartridges, they should be efficient, reliable and ergonomic. At the same time, they should protect the IOL and the incision structure.

8.2.4.1Objectives of Injectors Meant for Microincision

•Efficiency: These injectors should allow an easy, accurate and reproducible implantation through an incision of less than 2 mm, since phacoemulsification through incisions of less than 1 mm is now possible.

•Reliability: These injectors should assure the safety of implantation operations for the eyeball as well as the cartridge and the implant. The cartridge quality and the adequacy of the IOL-cartridge and the plunger-cartridge have a primordial importance. The reliability includes various aspects:

Protecting the integrity of ocular structures, not only at the corneal incision but also at the iris and the posterior capsule: An excessive stretch can lead to a postoperative defect in sealing, increasing the risk of infection. Any damage to the cartridge or implant can cause ocular structure damages of varied severity.

Protecting the integrity of the cartridge: The cartridge can have various damages. It could be a major damage due to bursting of the tip, medium damage due to bleaching and micro fracture of the tip, or minimum damage that can be translated as the “fish mouth” phenomenon or expansion of the cartridge tip. A damaged cartridge can prove to be particularly deleterious for the implant and can cause various damages, from a micro linear laceration in the paracentral optical region to a haptic rupture sometimes with a large optical laceration.

Protecting the integrity of the implant morphologically (optic and haptics should not be affected) as well as optically (bending and other operations necessary for implantation during the injection phase should not alter the optical quality of the implant): The implant surface should not get affected by the injection procedure. The occurrence of lubricant product transfer from the cartridge to the implant during the injection should be kept to a minimum. The microalterations of the implant may lead to adhesion of the inflammatory cells on the optic and could alter its optical quality. They could also induce fibrosis or opacification of the posterior capsule.

•Ergonomics: It can be interpreted as a greater ease in the use of injectors and a short learning curve. The maneuvres should be minimal, simple, fast, reproducible and accurate.

Very few studies on the injection systems are available.

Comparing the efficiency of the injection systems with that of the use of forceps, Mamalis et al. [6] remarked that the procedures of implantation with the use of forceps widens the incision more than the injections using an injector. These authors also remarked that with forceps the widening of the incision depends on the power of the implant: The incision gets wider with high-power implant, but in the case of injectors, the power of the implant does not affect the final size of the incision. In this study conducted on 100 patients, two types of implants and two types of implantation systems (forceps and injectors) were not specific to microincisions but only to the standard size incisions.

Only injectors achieve the objective of implanting through an incision of less than 2 mm.

Studying the actual size of microincisions in 2005, Alio et al. [1] proved that the injector–implant pair, Acri.Smart 48S (Acri.tech), allowed a safe injection through an incision of less than 1.9mm. This prospective study included 45 patients. The average size of the incision before implantation was 1.46mm (1.4–1.9mm). After implantation, the incision size was 1.5mm or less in 32 out of 45 cases, 1.7mm in 10 cases and 1.9mm in three cases.

Three years ago, we completed a pilot study of Akréos MI 60 (Bausch & Lomb) implant meant for microincision, whose structure was designed to optimize the postoperative intra-saccular behavior in terms of stability and posterior capsular opacification. The results at the end of the first year were published [7].

For this study, we used a resterilizable injector and a Medicel 1.8 Viscoglide cartridge (internal diameter 1.23 mm, external diameter 1.65 mm) with a smooth silicone plunger tip. The currently recommended injector (Viscoject, Medicel) is a single use type.

Twenty patients were divided into two groups based on the injection technique used. For 10 patients the injector bevel was inserted in the anterior chamber (IN group). For the remaining 10, the wound-assisted technique of injection was used (OUT group) (Fig. 8.20).

The minimum incision size after injection, measured with the help of calibrators inserted in the incision, was 2.2 mm for the IN group and 1.8 mm for the OUT group.

The incision sizes in the IN group were:

•2.11 mm before injection (minimum 2, maximum

2.3)

Fig. 8.18 Result of the Akreos MI 60 (Bausch and Lomb) pilot study. Stretch and size of incision after injection

•2.22 mm after injection, with an average stretch of

0.11 mm and a minimum size of 2.2 mm

The incision sizes in the OUT group were:

•1.77 mm before injection (minimum 1.7, maximum

1.9)

•1.86 mm after injection, with an average stretch of

0.09 mm and a minimum size of 1.8 mm

In case of the OUT group, we have also observed a significant reduction in the incision sizes with the expertise acquired (from 2–1.8 mm). We shall probably be able to reduce the incision sizes further by developing the technique (Fig. 8.18). We did not notice any complication.

•For the same Akréos MI 60 (Bausch an Lomb) implant, J. Alió et al. [3] proved that implantation using a Viscoject injector carrying a Viscoglide 1.8 mm cartridge, manufactured by Médicel (Medicel AG, Luchten 1262, CH-9427 Wolfhalden, Switzerland) and having a cartridge with an internal diameter of 1.23 mm, resulted in a slight enlargement of corneal incision when implanted through an incision of 1.68 ± 0.24 mm: the incision size in post-injection became 1.82 ± 0.16 mm, i.e. a variation of 0.14 ± 0.22 mm.

•Belluci et al. did not observe any significant modification in the incision size with the same implant and same injection system while using incisions of 2 mm.

•While studying the reliability of the injection systems meant for microincision, Mencucci et al.[8] used electron microscopy and studied the surface of two implants of microincision after an injection procedure using a special injector: the ThinRoller Injector meant for Ultrachoice 1.0 Rollable Thin Lens IOL and the Acri.shooter Injector meant for the Acrismart implant. Four implants of each type were studied and no significant modification in the morphology of implants was noticed after injection. A small-sized superficial scratch on the haptic was found on the ThinOptx implant of strong magnification. Therefore, it can be stated that inserting an implant through an incision of less than 2 mm does not modify the quality of its optic.

8.2.4.2 Characteristics of Sub-2 Injectors

Other than the ThinRoller injector meant for Ultrachoice 1.0 IOL, ThinOptx, most of the sub-2 injectors have a