(1)
Newcastle Eye Centre Royal Victoria Infirmary, Newcastle upon Tyne, UK
Electronic Supplementary Material
The online version of this chapter (doi:10.1007/978-3-319-59924-3_3) contains supplementary material, which is available to authorized users.
Following the removal of any residual soft lens material, the artificial intraocular lens (IOL) implant is inserted into the empty capsule bag. Common practice is to use a pre-loaded injector system to insert the IOL into the eye. There are many injectable systems on the market, and each manufacture has their own lens and injector design. Thus, each device system will have a recommended IOL preparation and implantation technique. Novice surgeons will need to be familiar with the injection device and implant used in their unit. Trainer and Trainee should discuss the precise specifics before surgery.
Refractive choice, biometry calculation, IOL materials and design, and IOL types are an essential part of phacoemulsification training. However, it is unlikely novice surgeons will implant any multi focal, toric or anterior chamber lenses in the early stages of training. As a result, only the fundamentals of mono-focal, single piece IOL insertion are described below.
3.1 Terminology
3.1.1 Phakia
Phakia is the presence of the patient’s own natural lens.
3.1.2 Pseudophakia
Pseudophakia is the replacement of the natural crystalline lens with an artificial lens during cataract surgery. An appropriately selected IOL can be placed in the capsular bag, the ciliary sulcus or the anterior chamber. During uncomplicated surgery, standard practice is to place the IOL into the capsular bag at the end of surgery.
The IOL consists of the central optic and attachments called haptics. The flexible haptics provide support to hold the optic centrally within the capsular bag. The point where the internal curve of each haptic meets the optic is the optic haptic junction. The meeting point of the outer haptic curve and the optic form what is known, for the purposes of surgical instruction, as the shoulder of the lens (Fig. 3.1).
Fig. 3.1
Intraocular lens anatomy. Optic (long arrow), haptic (short arrow), optic haptic junction (star), shoulder of lens (dotted arrow)
3.1.3 Haptic Terminology
The artificial lens is housed within an injector cartridge system. This ensures a folded lens can be inserted through a small corneal incision. Following injection of the IOL within the eye, the aim is to ensure the optic and haptics are placed within the capsular bag. Before the IOL unfolds completely, it can be directed through the capsulorhexis opening. As a result, it is simple to place the leading haptic, the associated shoulder and leading optic edge within the capsular bag. It may be harder to achieve complete placement of the opposite shoulder, trailing haptic and part of the optic (Fig. 3.2).
Fig. 3.2
Incomplete IOL in-the-bag placement. IOL has just been injected and is starting to unfold. Leading haptic (short arrow), trailing haptic (long arrow). Air bubble artefact (arrow head)
For complete in-the-bag placement the remaining part of the IOL (namely, the optic and the trailing haptic) will require manipulation into the bag. This is commonly referred to as dialling. Occasionally, if the lens is injected above the capsulorhexis then the whole lens may unfold outside of the capsule bag. In this instance, both haptics as well as the optic will need to be dialled into the bag.
3.2 Lens Implant Orientation
Modern lenses have aspheric design (to minimise spherical aberration) and are commonly vaulted slightly backwards. In view of this, the IOL ideally needs to be orientated correctly within the capsular bag. During insertion, however, the IOL may inadvertently flip over. Although it is possible to place an upside-down lens in the bag, it is not ideal as this can affect the final refraction. An upside-down lens can be recognised as the haptic and optic of an upside-down lens will form the letter “S” (Fig. 3.3). If this happens, the surgeon should stop and manipulate the orientation of the IOL accordingly. Reorientation before in-the-bag placement is performed by gently rotating the lens implant, either by pivoting the IOL using the trailing haptic as a handle, and/or by directly manipulating the optic within the eye (Fig. 3.4).
Fig. 3.3
Intraocular lens orientation . (a) Correct placement, (b) incorrect placement with upside down implant. Haptic (long arrow) and optic (short arrow) form letter S when implant is upside down (solid line)
Fig. 3.4
Intraocular lens orientation. (a) Upside-down orientation of 3-piece IOL. Leading haptic (solid arrow) is partly under the capsulorhexis edge, trailing haptic (open arrow) has not been inserted into the eye. (b) Intraocular lens correctly orientated. Leading haptic (solid arrow) is under the capsulorhexis edge, trailing haptic (open arrow) has not been inserted into the eye
3.3 Step-by-Step Technique
The aim of IOL placement is to inject the lens into the anterior chamber and ensure it is correctly placed into the capsular bag via the capsulorhexis opening. Care is required to ensure the capsule, zonules or other ocular tissues are not traumatised during the process.
3.3.1 Step 1
The injecting cartridge system is prepared as per the manufacturer’s guidance.
It is preferable to only leave a small amount of viscoelastic within the cartridge nozzle ahead of the lens when priming the injector. Too much viscoelastic in the nozzle can lead to overfilling of the capsule bag as the lens and accompanying viscoelastic is injected into the eye. The surgeon should avoid priming the injector excessively as this may result in partial exposure of the lens from the injector nozzle tip. In this situation it may not be possible to insert the injector nozzle into the eye. Conversely if the surgeon decides a small top up of viscoelastic is required (despite filling the eye previously with viscoelastic) a greater quantity of viscoelastic can be left within the nozzle before the lens is injected. The Trainer will advise on this.
3.3.2 Step 2
The capsule bag needs to be filled with viscoelastic. This buffers and protects the ocular tissues (especially the capsular bag) as the IOL is inserted. If a small amount of viscoelastic is expelled just before the cannula is inserted into corneal section any air trapped in the cannula hub is flushed out. This avoids inadvertently injecting any air, if the viscoelastic syringe has not been primed, (an example of an air bubble within the anterior chamber is shown in Fig. 3.2). Air bubbles do not hinder the insertion of the IOL and can be directed to the periphery, to avoid obscuring the central view, simply by injecting more viscoelastic. Following lens implantation, any bubbles are easily aspirated during viscoelastic removal.
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