Four year old with LEC migration approaching visual axis. Three piece MA30 acrylic IOL “in the bag” after anterior CCC, lensectomy, posterior CCC and anterior vitrectomy carried out in infancy
The use of rigid PMMA IOLs has been shown to be associated with a higher risk of complications such as anterior capsular tears, iris prolapse, optic displacement anterior to the capsule, optic capture of the pupil and fibrinous uveitis. This is likely to be due to the larger wound size needed for their insertion , and the associated operative and post-operative complications (uveitis, pigment deposition, iridocorneal adhesions and posterior synechiae). However IOL type (PMMA or acrylic) does not appear to significantly influence the incidence of PCO following cataract surgery in children  but onset of significant PCO may be inhibited for longer following acrylic IOL insertion [10–13].
9.3 Technique of IOL Insertion
The authors prefer corneal incisions (rather than limbal or scleral). A superior incision with a keratome is made at the start of the lensectomy procedure and temporarily sutured closed again once it has been used for access to perform a capsulorhexis with forceps under viscoelastic. This suture maintains the stability of the anterior chamber of the eye for the subsequent lensectomy. Two incisions with an MVR blade are made at 90° to this incision i.e. at 3 and 9 o’clock and are used for the vitrector and infusion cannula. The lensectomy is performed as outlined in Chap. 7 (Wilson). An alternative technique is to use vitrector forceps for capsulorhexis using one of the two MVR incisions. One of these can then be enlarged after the lensectomy to enable IOL implantation (rather than using 3 incisions). In either approach, the corneal wound utilised is enlarged to approximately 3.0 mm in length, prior to insertion of the IOL. The capsular bag is filled with viscoelastic in order to ensure that the anterior and posterior capsules are well separated and thus provide sufficient space within the capsular bag for IOL insertion. Single piece pre-loaded injectable IOLs (for example the Acrysof SN60AT) may be used even in the presence of a posterior capulotomy . However they require careful insertion as the leading haptic can snag on a weak or defective posterior capsule causing further capsular trauma and lens luxation into the vitreous cavity. This should be guarded against in cases of posterior lenticonus (Fig. 9.2). The single-piece SA60 IOL is folded into an IOL introducer which has been primed with viscoelastic. The introducer is inserted through the enlarged corneal wound into the plane of the anterior capsule and the lens is injected into the capsular bag gently, taking care not to inject the lens through the posterior capsule or disrupt the capsular bag.
Large oval posterior lenticonus defect apparent in eye of infant (prior to IOL insertion) after anterior circular capsulorhexis and lensectomy
A 3-piece IOL (for example the Acrysof MA30AT or MA60AT) can be placed directly in a controlled manner within the capsular bag and so may be less technically challenging in the presence of a posterior capsulotomy in younger children. The 3 piece Acrysof MA60AT and MA30AT lenses are folded manually in forceps and inserted through the enlarged corneal wound. The leading haptic is inserted through the wound first and placed carefully in a flat plane into the equator of the capsular bag, taking care not to snag or disrupt the posterior capsulotomy. The optic follows through the corneal wound and is allowed to slowly unfold in the plane of the anterior capsule. The trailing haptic is then grasped with forceps and, via pronation of the surgeons wrist, rotated into the plane of the capsular bag, whilst the optic is depressed gently with a second instrument (such as a lens dialler) introduced through the paracentesis. This ensures that the trailing haptic follows the optic into position within the capsular bag once gently released and that any dialling of the lens is minimal or unnecessary.
9.4 IOL Position
There are several options open to the surgeon with regard to the position of the IOL in relation to the capsular bag.
The IOL can be positioned completely within the capsular bag between the anterior and posterior capsules (as in traditional adult extracapsular surgery) (Fig. 9.3). However in the presence of an abnormal, torn or unstable posterior capsule, optic “capture” can be achieved so that the lens haptics are placed anterior to the capsular bag, in the ciliary sulcus, with the optic of the IOL pushed posteriorly through an intact anterior capsulorhexis so that the optic is within the plane of the capsular bag. Other useful techniques to consider include placing the haptics in the sulcus but capturing the IOL through both the anterior and posterior capsulorhexes (optic behind the posterior capsule), or the haptics can be positioned within a capsular bag with posterior capture of the optic of the IOL through a stable posterior capsulorhexis (optic buttonholing) [1, 2, 15, 16]. Optic capture is performed in each of these techniques after initial positioning of the haptics (with adequate viscoelastic maintaining the anterior chamber). Gentle pressure is applied to the lens optic with a manipulator to push it through the capsular opening (Diagrams 9.1, 9.2, 9.3, and 9.4).
Two year old with one piece SA60 acrylic IOL “in the bag” immediately after procedure – anterior CCC, lensectomy, posterior CCC and anterior vitrectomy
Five year old with well centred one piece SA60 acrylic IOL “in the bag” 2 months after anterior CCC, lensectomy, posterior CCC and anterior vitrectomy
Diagrams 9.1, 9.2, 9.3, and 9.4
Sequence of images showing a three piece IOL converted from initial “in the bag” implantation to optic capture through a posterior CCC (Graphic by Dr C Kilduff)
IOL implantation within the capsular bag produces a stable IOL with a reduced risk of post-operative inflammation compared to a sulcus fixated IOL. However IOL capture may provide stability and long-term centration of the IOL and prevents vitreous from extending anteriorly , and may reduce the incidence of and/or delay the onset of VAO [17, 18].
A technique, known as ‘bag-in-the-lens’ IOL implantation, has been used extensively in Europe . Anterior and posterior capsulorhexes are performed of a similar size (5.0 mm) and, following IOL insertion, both leaves of the capsule are positioned into a groove between two flanges around the circumference of the IOL. This technique aims to eradicate lens epithelial cell (LEC) proliferation and migration by confining the LECs to the rim of capsular bag around the IOL.
9.5 When to Perform a Posterior Capsulotomy and Anterior Vitrectomy
Visual axis opacification (VAO) occurs rapidly and universally in young children when the posterior capsule is left intact, due to the greater tissue reactivity of younger lens epithelial cells (LEC) [1, 2]. Performance of a primary posterior capsulotomy (PCC) and anterior vitrectomy at the time of surgery reduces the incidence of, and delays the onset of, VAO [13, 16, 18, 20, 21] (Fig. 9.4). There remains uncertainty about the precise age up to which PCC and anterior vitrectomy is needed. It is undoubtedly also influenced by factors such as likely compliance with follow-up and access to a horizontally mounted Nd-YAG laser for capsulotomy. VAO is reported to be significantly higher in children aged 8 years and younger at the time of surgery . Other authors suggest that PPC is advisable when cataract surgery is carried out at less than 6 years old .
PCC alone is less effective in delaying or preventing VAO than PCC combined with anterior vitrectomy [18, 24], as the intact anterior hyaloid face may act as a scaffold for LEC migration and proliferation across the visual axis. PCC with posterior optic capture has been suggested as a technique to delay VAO in the absence of anterior vitrectomy , but it appears to be more effective in the prevention of VAO when combined with anterior vitrectomy . Other studies have suggested that PCC and anterior vitrectomy are important steps in maintaining a clear visual axis after cataract surgery in patients younger than 7 years of age . The authors perform PCC and anterior vitrectomy in all children of 5 years of age or younger.
9.6 Posterior Capsulotomy Techniques
Several techniques are available for performing posterior capsulotomy, and the one chosen will depend on the clinical features of each individual case, the surgeons experience and preference, and the equipment available. Frequently used techniques include a manual continuous curvilinear capsulorhexis (CCC), the ‘two incision push pull’ technique, and vitrectorhexis through a pars plana sclerostomy. The paediatric cataract surgeon should be comfortable performing PCC via a variety of techniques. This enables posterior capsulotomy to be carried out in a range of clinical situations, for example in the presence of a pre-existing posterior capsular defect or a posterior capsular plaque.
Posterior capsulotomy and anterior vitrectomy may be performed prior to insertion of the IOL (via manual CCC, ‘two incision push pull’ technique or vitrectorhexis followed by anterior vitrectomy). It can also follow IOL insertion (via vitrectorhexis from an anterior approach behind the IOL, via a pars plana incision with vitrectorhexis or via manual CCC followed by anterior vitrectomy. When PCC is carried out prior to IOL insertion, trypan blue 0.06 % may be used to enable better visualisation of the posterior capsule if necessary . This is instilled under viscoelastic and then the anterior chamber irrigated with balanced salt solution.
The posterior capsulotomy may be carried out with the vitrectomy cutter (vitrectorhexis) prior to insertion of the IOL, by insertion of the vitrector through a corneal paracentesis, and fashioning of a posterior capsular opening with the cutter under viscoelastic. The posterior capsulotomy should ideally be smaller than the size of the anterior capsulorhexis (approximately 4 mm), round and centrally placed so that the visual axis is cleared. This technique may be difficult in the presence of a posterior capsular plaque (for example in cases of persistent fetal vasculature) when intraocular forceps and/or scissors may be needed for removal of the central capsule. In cases of posterior lenticonus the posterior capsule is often very thin and friable and thus easily amenable to opening with this technique. If there is a pre-existing capsular defect, this can similarly be enlarged or trimmed as necessary with the cutter.
Some surgeons prefer to perform a manual posterior CCC; an initial opening is made in the posterior capsule using a needle following inflation of the capsular bag with viscoelastic, and then the capsulotomy is completed with forceps . The CCC should be well centred and smaller than the anterior capsulorhexis. Excess injection of viscoelastic posterior to the capsule through the central puncture may increase the potential for the CCC to tear out to the equator.
The ‘two-incision push-pull’ capsulotomy technique has been well described [29–29] and is reported to provide a reliable method of making the posterior capsular opening; two parallel incision are made in the posterior capsule with a needle under viscoelastic, and these are then extended with forceps to create a central posterior capsulotomy opening. Hamada et al reported no incidents of inadvertent vitreous loss in 41 cases undergoing the two incision push pull technique for posterior capsulotomy . This method can result in an oval rhexis and so a four-incision technique has been described in order to improve the configuration of the posterior capsulotomy (Mohammadpour JCRS) .