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Ординатура / Офтальмология / Английские материалы / Minimally Invasive Ophthalmic Surgery_Fine, Mojon_2010.pdf
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J. L. Alio et al.

5.4.1.2 Types of Phakic Intraocular Lens

We will discuss two PIOLs which require sutureless incisions of less than 3 mm and, therefore, more closely achieve the goals of minimal incision surgery for PIOL.

5.4.1.3 Kelman-Duet Phakic Intraocular Lens

The Kelman-Duet PIOL (TEKIA, Irvine, CA, USA) is an angle-supported PIOL. What makes it different from other angle-supported PIOL is that it has an independent haptic and a separate optic frame of 6 mm (Fig. 5.12). The main advantage is the ability to implant this lens through a sub-2.5 mm sutureless incision. This allows the refractive surgeon to perform this surgery under topical anaesthesia. Another advantage of this lens is the exchangeability of both the lens haptic and optic. It is known that the human myopic eye may experience optical and refractive changes such as progressive myopia, presbyopia or changes in lens asphericity throughout the lifespan. Exhangeability of the optic is an option that allows the implant to be adapted for these future refractive changes. Another important advantage of this lens is the possibility of selecting the appropriate size of the haptic depending on the anatomic characteristics of the anterior segment. This

Fig. 5.12 The Kelman-Duet two-piece phakic intraocular lens

enables a specific complication of angle-supported PIOLs (i.e. pupil ovalisation due to inappropriate selection of the size of lens) to be solved.

Lens Design

The Kelman-Duet lens is a two-piece, angle-supported PIOL, consisting of the haptic and optic. Both parts are independent and implantable through a sub-2.5 mm incision. The polymethylmethacrylate haptic has three points of support and harbours a central area with two anchors to engage the optic of the lens. The total length of the haptic is from 12 to 13.5 mm. The haptic supporting tips are rounded and oval to ensure smooth contact with the angle structures. The angulations of the haptic are 11.1° for the 12.0 mm haptic, 10.5° for the 12.5 mm haptic and 9.6° for the 13.0 haptic.

The mono-focal optic is made of silicon and has a total diameter of 6 mm, with two eyelets to be attached to the haptic frame. It can be injected through a sub- 2.0 mm incision. The periphery area of the optic has a glare-preventing shield to avoid light reflexes in dimlight conditions. The optic is available in 1-diopter increments in optic power from −6.0 to −20.0 D.

Surgical Technique

Pre-Operative Preparation

It is recommended that all patients undergoing KelmanDuet implantation should have had a Visante AS-OCT scan of the eyes. The anterior chamber depth (as measured from the endothelium to the anterior lens surface), cornea–iris angle measurement and sulcus- to-sulcus measurements are important in deciding whether the patient’s eye is suitable for the KelmanDuet PIOL. Pre-operative endothelial cell counts are also essential. Eyes undergoing the Kelman-Duet PIOL implantation should fulfil the following criteria:

1.Mean endothelial cell density of more than 2,500 cell/cm2

2.Anterior chamber depth of more than 3.0 mm

3.Cornea–iris angle of more than 35°

4.Sulcus-to-sulcus measurement of more than 11.0mm

Implantation of the Kelman-Duet PIOL can be performed under topical anaesthesia. In our centre, pre- servative-free lidocaine 2% is used with mild sedation