23.2.1 Evaluate Capsular Support

The status of the capsule and bag is the most important factor influencing IOL placement and technique. Several key factors regarding the capsule/bag must be evaluated prior to IOL implantation, include presence of the bag, status of the anterior capsule, status of the posterior capsule, status of the zonular instability (focal or diffuse loss), and presence of a capsule tension ring (CTR) (Table 23-1).

Should the entire bag be absent, it is inadvisable to proceed with placement of a single-piece foldable IOL for scleral suturing, although closed-loop haptic lenses have been scleral fixated. ² One should then consider either sutureless intrascleral haptic fixation (see Chapter 24) or iris-sutured fixation of a three-piece lens (see Chapter 22), or scleral suture fixation of a three-piece or specially designed polymethyl methacrylate (PMMA) lens with suture eyelets.

If the posterior capsule is intact, or even in the case of a small posterior capsule tear, a single-piece foldable IOL and CTR may be placed in the bag with weak zonules. For posterior capsule tears, conversion to a more stable posterior continuous capsulorhexis is preferred so that small tears do not radialize with the manipulations involved in CTR and IOL insertion. ³ Plate haptic designs would not allow for haptic suturing; therefore, in severe zonule weakness requiring scleral fixation these lenses should be avoided. Once the IOL is in the bag, the haptics can be sutured through the bag to the sclera as described following here.

If the posterior capsule opening is too large for bag placement of an IOL, but the anterior capsule remains intact, then the anterior capsule can serve as a support scaffold. Even in cases with significant zonule weakness, a three-piece intraocular lens can be used to reverse optic capture the lens with the haptics behind the posterior capsule (see Chapter 19). These haptics can then be scleral sutured through the bag, and the IOL optic can either remain in the sulcus or be positioned behind the anterior capsule once the haptics are secured.

If zonule loss is focal, then orienting the haptics on axis with the area of weakness will aid in centration of the IOL without extensive suture fixation. In this scenario, the haptic in the area of focal zonule loss can be sutured to the sclera, and, if the remaining bag/zonules are functional, this may be the only point of fixation that is needed. ⁴

If zonule loss is diffuse the decision whether or not to keep the bag must be made. A bag may be salvaged despite significant zonule loss by implanting and scleral suturing two capsule tension segments 180° apart in addition to CTR insertion. An IOL can then be safely implanted in the bag. Alternatively, a safety “basket” mattress suture can be placed to support the IOL while scleral suturing or intrascleral haptic fixation is performed. ⁵

Severe and diffuse zonule loss may be treated as if the capsular bag is absent after removing the bag because IOL placement in the bag, even for scleral suture fixation, may result in the IOL/bag complex dropping into the posterior segment. The bag can be held in position with capsule retractors or capsule tension segments, followed by IOL implantation, followed by scleral fixation, but this carries the risk of capsular tears that can destabilize the entire complex before the haptics have been fully secured.

CTRs are commonly used in cases with weak zonules, and these devices can actually aid in scleral suture fixation. Because the device is ideally present for 360°, suture fixation of the CTR to the sclera can be more forgiving than trying to suture around haptics within the bag. Fixation points can now be placed anywhere along the CTR and are not limited by haptic placement. The surgeon may decide to suture fixate in an orientation that is most ergonomic.

23.2.2 Managing Vitreous

Vitrectomy should be performed in order to minimize traction on the vitreous and retina during intraocular manipulations. In cases of IOL dislocation, vitrectomy is performed to adequately free the IOL and/or bag complex from vitreous, although care must be taken because this can destabilize the IOL further as vitreous is cleared. Vitrectomy may also be performed in areas of planned suture passes, especially in areas where the hyaloid has already been disturbed. Vitrectomy in areas with an intact hyaloid can actually increase the chance of vitreous presentation into the anterior chamber (AC) because vitreous was previously intact and undisturbed. The use of preservative-free triamcinolone can aid in vitreous visualization and should be used to ensure that it has been adequately cleared. ⁶ Key principles to optimal vitrectomy in cases requiring scleral fixation include minimizing chamber fluctuations so that vitreous does not present anteriorly, using a two-handed approach, and even dry vitrectomy when needed, avoiding excessive/unnecessary vitrectomy that can increase the risk of retinal complications.

23.2.3 IOL Selection

As already discussed, IOL model selection can depend on the status of the capsular bag. Modified PMMA lenses with eyelets along the haptics are one-piece lenses with varying optic sizes that are designed for scleral suture fixation and include the Alcon CZ70BD, the Bausch and Lomb 6190B, and the Pharmacia U152S by Abbott Medical Optics, Inc. (AMO). Alternatively three-piece foldable IOLs and single-piece acrylic IOLs may be used, depending on the amount of capsule that remains.

Selecting an IOL power when scleral fixating an IOL has been poorly studied. Scleral fixation will result in the IOL sitting posterior to the usual in-the-bag location. Therefore, using the in-the-bag calculations but targeting 0.5 to 0.75 diopters (D) of myopia should in general allow for near-emmetropia results with less risk of a hyperopic surprise than if the surgeon chooses an emmetropic target from in-the-bag placement options (unpublished results of the authors’ cases). Adjusting IOL power aiming for slight myopia (higher IOL power) will account for the more posterior position of an IOL that is scleral fixated in comparison to in-the-bag placement or iris fixation.

23.2.4 Suture and Needle: Type and Placement

Several considerations should be made when selecting the suture material and needle. In young patients, permanence is paramount, although, given the increasing average life expectancy in adults, the authors now prefer suture fixation with expanded polytetrafluoroethylene (ePTFE) (GORE-TEX, W. L. Gore and Associates). Currently this is not approved for ophthalmic use, and the smallest-size suture is a 7–0 equivalent (labeled by the manufacturer as a CV-8 thread size). The TTc-9 needle is a taper point, 3/8 circle needle 9 mm in length. The authors prefer to straighten the needle for ease of use (Fig. 23.1). This suture has been used in scleral fixating IOLs without complications, despite its off-label use.s. Literatur ^{,​ 8} Other suture types include polypropylene sized either 9–0 or 10–0 on long curved needles, including the Ethicon CIF-4 and the Alcon PC-7. Concern remains over the permanence of polyprolylene, ^{9 ,​ 10} but no direct long-term comparison between suture materials has been published. In general, larger-caliber suture should last longer than smaller-caliber suture of the same material.