Preloaded systems compared

Optic or haptic damage has previously accounted for over 14% of intraoperative foldable lens explantations.¹ However, an increasing focus on operating procedure standardization and strict guidelines regarding the reuse of materials have led to a rising trend in the use of disposable materials. Consequently, foldable lenses and injector systems are now used as standard in routine cataract surgery, thus simplifying the logistics in the operating theatre and reducing complication rates.

There is considerable variation among the individual systems; whether fully- or semi-preloaded however, several rules apply to all: the injector must be safe, the function reproducible and the unit sterile during the specified shelf life. The surface coated cartridge and the plastic material of the injector stamp must also offer both a sufficient degree of flexure, strength and elasticity. These characteristics do, however, limit the diameter of the cartridge tip to around 2.5 mm at the moment.

The clinical argument for preloaded lenses is convincing. Because insertion of the lens into the cartridge, frequently performed macroscopically, is no longer necessary, there is no additional risk of contamination, no mechanical damage because of contact with the lens by instruments, no 180º upside-down confusion, and no loss of the IOL on the operating table. Injection of the IOL is standardized. The injector systems themselves are all disposable materials; there is absolutely no more need for complicated preparation of the instruments for re-use.

There are currently seven preloaded systems available on the market in Germany: four fully preloaded (manufactured by Hoya, Alcon, STAAR-Domilens) and three semi-preloaded (manufactured by Polytech, Zeiss, Technoko) (Table 1). Insertion of the cartridge into the injector is required by the surgeon for semi-preloaded systems.

Table 1.Overview of preloaded IOL systems.

All seven manufacturers offer one silicone lens, two hydrophilic and four hydrophobic acrylic IOLs. Around 50% of the lenses contain a blue-light filter. This accurately reflects the current market share of IOL materials in Germany. Of all these lenses, Polytech offers the broadest diopter spectrum, two different optical diameters (6.0 mm and 6.5 mm) as well as an optional blue-light filter. The hydrophilic acrylic IOLs, with their low total diameter and special haptic design without a C-loop, are very comfortable with regards to the implantation procedure, but they must be implanted on a strictly intracapsular basis and presume a surgery free from complications and a stable zonula apparatus or an additional capsular tension ring implantation. There are few clinical long-term studies regarding centration and capsular opacification behaviour. The one-piece hydrophobic IOLs should not be implanted into the sulcus due to a lack of haptic angulation; this is possible with three-piece models, however.

Potential in the further development of preloaded systems lies in a fully standardized and reproducible lens removal from the cartridge with minimal prior manipulations to the injector system and smaller incision breadths. For everyday routine operations, preloaded IOL systems facilitate the procedures and enable a greater degree of safety.

Reference
1. J.M. Schmidbauer, et al. J. Cataract. Refract. Surg. 2002;28(7):1223–1228.

Author
Heike Häberle works at the Vivantes Netzwerk für Gesundheit GmbH, Berlin, Germany.