As primary or secondary implantation after cataract surgery, in a patient with inadequate capsular bag support.

The prerequisites for an ACIOL implantation include good corneal endothelial health, intact iris architecture, normal anterior chamber depth, normal anterior chamber angle (if there is peripheral anterior synechiae, it should be less than 2 clock hours in extent), and a patent and generous peripheral iridectomy (preoperative or intraoperative) [4]. Several authors have cautioned against implantation of ACIOL in patients less than 50 years of age [1, 5].

There are two parameters for ACIOL selection, IOL power and IOL size. The IOL power is determined by using the A-constant of the ACIOL or, as a rule of thumb, reducing the calculated in-the-bag IOL power by three diopters, which is the approximate difference of A-constants of an anterior chamber implant from an in-the-bag IOL implant [1].

The other important issue is selecting the ACIOL of appropriate size, because both an oversized and an undersized ACIOL are detrimental to the eye. The recommended haptic-to-haptic diameter of an ACIOL is 1 mm more than the horizontal white-to-white corneal diameter (HWWCD) [1]. This is only an initial guide, and appropriate sizing can be determined only after implantation. Implantation of an oversized ACIOL will result in ovalization of pupil intraoperatively, and in the long run is prone to cause ocular discomfort and angle erosion. On the other hand, implantation of an undersized ACIOL will be observed intraoperatively as excessive mobility of the implant, and in the long run is prone to cause endothelial compromise, hyphema, uveitis, and cystoid macular edema.

Characteristics of a modern ACIOL include a flexible open-loop design (Kelman multiflex style), which has a lower incidence of complications than the previous designs [6]. The open-loop design prevents excessive anterior vaulting inside the eye. There is slight anterior vaulting inherent in the ACIOL design to minimize IOL-iris touch [7]. These IOLs have only four points of highly polished contacts (foot-plates) with the angle, which minimize goniosynechiae formation and make them easier to explant, if required [8].

Also, secondary implantation of an ACIOL has been found to have a better outcome when compared to primary implantation of an ACIOL [9, 10].

A good anterior vitrectomy and a generous peripheral iridectomy are prerequisites for implanting an ACIOL. The pupil should ideally be round and small. The ACIOL should go smoothly into the anterior chamber angle with the foot-plates resting on the scleral spur, and should not engage (or snag) the iris [11]. The haptics of the ACIOL should be away from the site of peripheral iridectomy [11]. The proximal haptic should lie beneath the lower lip of the incision, or the two haptics should be rotated perpendicular to the incision site [1].

The complications that have been reported following ACIOL implantation include corneal decompensation [10], iris tuck [12], uveitis-glaucoma-hyphema (UGH) syndrome [7], lens dislocation [12], and cystoid macular edema [10]. A good anterior vitrectomy has been found to significantly reduce the incidence of glaucoma [13]. Ravalico et al. [14] found that there was no significant difference in short-term and long-term endothelial compromise in eyes with ACIOL implantation when compared to fellow eyes with PCIOL implantation, and suggested that it is the surgical trauma, rather than a properly implanted ACIOL, which causes endothelial decompensation. Fintelmann et al. [15] described severe iris chafe and related complications after upside-down implantation of ACIOL in four patients due to posterior vaulting of the ACIOL.

As primary or secondary implantation after cataract surgery, in a patient with inadequate capsular bag support, as an alternative to ACIOL.

The prerequisite for an iris-fixated IOL is a normal iris architecture. For an anterior iris claw IOL, the prerequisites are similar to that of an ACIOL. For iris suture fixation of IOL, patients requiring posterior segment examination postoperatively, such as diabetic retinopathy, should be excluded [1].

Iris-fixated IOLs are of three designs. Anterior iris claw IOL [16–21], posterior iris claw IOL [22–24], as well as suture-fixated IOL [16, 25–29] are suitable options when there is absent or incomplete capsulozonular support. Suture fixation to the iris is a suitable option in case of late postoperative decentration of a three-piece IOL, which had been originally placed in the sulcus or capsular bag [30]. For posterior iris claw and iris-sutured IOLs, the IOL power determination is similar to that of a sulcus-fixated IOL. For anterior iris claw IOL, the IOL power determination is similar to that of an ACIOL.

Kukner et al. described an innovative method of implanting a PCIOL in the anterior chamber by passing the haptics to the posterior chamber through two iridectomies and observed good results for a mean follow-up period of more than 2 years [31]. Another technique of suture fixation of an IOL to the iris which has been described is by suturing a four-holed optic to the iris [26].

Key prerequisites for iris fixation include peripheral iridectomy, intracameral pilocarpine injection for miosis, and viscoelastic use for protecting the corneal endothelium.

For enclavation of an iris claw IOL to the iris, forceps are used to hold the IOL in place, while the iris is engaged to the IOL with another instrument [1].

For suture fixation of a three-piece IOL, the optic is first prolapsed in front of the pupil while the haptics remain in the sulcus [32]. 9-0 or 10-0 polypropylene suture is used in a McCannel technique to fixate one or both haptics to the iris.

The complications associated with iris fixation of IOL include iris chafe [33] and iridodialysis [34]. Iris chafe can lead to chronic iritis, raised intraocular pressure, and cystoid macular edema [19, 22]. The incidence of iris chafe can be reduced by placing iris fixation sutures as peripherally as possible and avoiding too tight or too broad knots [1].

As primary or secondary implantation after cataract surgery, in a patient with posterior capsular rupture, but with an adequate anterior capsular rim. The minimum requirement of anterior capsule remnant for sulcus implantation of IOL has been described to be at least 90° of anterior capsule rim for each haptic [35].

An adequate anterior capsular rim.

The most important consideration for a sulcus-fixated IOL is the material and design of the IOL [36]. A single-piece hydrophobic acrylic IOL should never be implanted in the sulcus. These IOLs have bulky haptics, square optic-edge profile, and some, like the Acrysof (Alcon Surgical, Fortworth, Texas, USA) IOL, in addition, have a planar haptic-optic angulation, which leads to rubbing against the uveal tissue, leading to uveitis, hyphema, and glaucoma (UGH syndrome). These IOLs also have inadequate diameter, making these lenses prone to decentration following sulcus placement. The appropriate IOLs for sulcus implantation are a three-piece foldable IOL or a rigid polymethylmethacrylate (PMMA) IOL. The ideal three-piece IOL for sulcus implantation should have an optic diameter of at least 6 mm, haptic-to-haptic diameter of at least 13 mm, a rounded anterior optic edge, a posteriorly angulated haptic-optic configuration, and no inherent asphericity. For a larger eye, with a horizontal white-to-white diameter of 12.0 mm or more, the ideal IOL diameter should be 13.5 mm. Among the three-piece IOLs that are available, AQ-2010 AV (STAAR Surgical, Monrovia, California, USA) has a 6.3 mm optic diameter, a 13.5 mm haptic-to-haptic-length, and a rounded anterior optic edge, but is made of silicone. The MA50 IOL (Alcon Surgical, Fortworth, Texas, USA) is a hydrophobic acrylic IOL with an optic diameter of 6.5 mm, but has a square anterior optic edge and a 13.0 mm haptic-to-haptic diameter. The Sensar IOL (Abbott Medical Optics, Santa Ana, California, USA) is a hydrophobic acrylic IOL with a rounded anterior optic edge (OptiEdge design), a 13.0 mm (+6.0 D to +30 D) or 13.5 mm (−10.0 D to +5.5 D) haptic-to-haptic diameter, and a 6.0 mm optic diameter [37].

The other important issue in selection of a sulcus-fixated IOL is IOL power selection. If it seems that the IOL optic can be captured behind the intact anterior capsular rim, IOL of same power as that calculated for in-the-bag IOL placement can be selected [38]. Otherwise, if optic capture does not seem possible, the power selected for sulcus placement should be adjusted. According to Dr. Hill, IOL power adjustments, for sulcus implantation, from the calculated in-the-bag IOL power are as follows: no change for calculated in-the-bag IOL powers less than or equal to +9 D, 0.5 D reduction for calculated in-the-bag IOL powers from +9.5 to +17 D, 1 D reduction for calculated in-the-bag IOL powers from +17.5 to +28 D, and 1.5 D reduction for calculated in-the-bag IOL powers from +28.5 to +30 D [39].

The important issues for implanting a sulcus-fixated IOL are first determining the integrity of the anterior capsular rim before selecting this method of IOL fixation and then opening up the space between iris and anterior capsular rim with viscoelastic before implantation. In case of an anterior capsular rim with a single radial tear, the haptics of the IOL should be positioned at right angles to the tear.

Gimbel et al. [40, 41] have described suturing the haptics of a subluxated sulcus-based IOL to the fibrotic remnants of the capsule to ensure sulcus positioning of the IOL and avoiding iris touch.

The complications associated with sulcus placement of IOL include UGH syndrome (particularly associated with single-piece hydrophobic acrylic IOL) and decentration of IOL. Rarely, UGH syndrome has also been described after sulcus implantation of a three-piece foldable IOL [42].

As primary or secondary implantation after cataract surgery, in a patient with an inadequate capsular bag support. This is particularly suitable for a patient with a damaged anterior segment, with compromise of structure and function of cornea, anterior chamber angle, and/or iris. This technique is also indicated in subluxated or dislocated sulcus or in-the-bag IOL [43, 44].

A scleral-fixated IOL is the most versatile method and can be used in almost any situation of aphakia. One situation where this option may not be preferred is a patient on anticoagulant medication.

The ideal IOL for suture fixation to the sclera should have an optic diameter of 7 mm [45].The IOL power is similar to that of an IOL selected for sulcus implantation. Scleral fixation of IOL can be done in two ways, suture fixation and sutureless intrascleral haptic fixation. For suture fixation to sclera, rigid PMMA IOLs, with eyelets in the haptics, are used. Rigid PMMA IOLs without eyelets can also be suture-fixated to the sclera, but the former are preferred. For sutureless intrascleral haptic fixation, a three-piece IOL is preferable. Rigid PMMA IOLs can also be used for sutureless scleral fixation, but they tend to break and have to be handled carefully.

Several methods of suture fixation of IOL have been described [46–57]. In general, the two scleral flaps should be diagonally opposite to each other, and the scleral entries under the scleral flaps should be equidistant from the limbus, so that the IOL is properly centered. For this, a radial keratotomy marker and a caliper can be utilized. Thinned areas of sclera should be avoided for making scleral flaps. A good anterior vitrectomy is essential. For suture fixation to the sclera, 9–0 polypropylene or 8–0 polytetrafluoroethylene (Goretex) suture material should be used. Ram et al. have described use of steel sutures for scleral fixation of IOL [58].The fixation sutures, as well as the IOL haptics, should ideally be located in the ciliary sulcus region, to minimize disturbance of the blood-aqueous barrier. To ensure this, several methods have been described, including ultrasound biomicroscopy [59], transillumination [52, 60], endoscopy [61], and variation of surgical techniques [61]. Trimarchi et al. [62] found that an internal suture pass method best ensures sulcus positioning of the IOL. A knotless suturing of the IOL to sclera, with the help of multiple intrascleral passes of the suture, has also been described [50, 51, 63, 64].

For sutureless intrascleral haptic fixation, each IOL haptic is externalized through the scleral entry and is inserted into an intrascleral tunnel, with or without scleral flaps. If scleral flaps are made, the flaps are repositioned with fibrin glue [65]. Fibrin glue secures the scleral flaps but has little direct role in stabilizing the haptics of the IOL. The scleral flaps can also be repositioned with sutures, instead of glue. The details of these techniques will be dealt with in more detail in another chapter. Yamane et al. [66] have also described a variation of sutureless intrascleral haptic fixation with the help of a 27-gauge needle to exteriorize the haptic. Ladi et al. [67] have discussed the advantages of vertical IOL orientation for scleral fixation compared to horizontal orientation.

The complications associated with sutured scleral-fixated IOL include external suture erosion, with or without scleral flaps [68, 69], and subsequent decentration of the IOL [70–72] and suture-wick endophthalmitis [73]. Retinal tears leading to retinal detachment, after scleral fixation of IOL, have been found to be located more often in the axis of IOL haptic and suture [74]. Hyphema [75], vitreous hemorrhage [75], and suprachoroidal hemorrhage [64] are also known complications of scleral fixation of IOL. Sutureless fixation of IOL to sclera is a relatively new technique, and long-term result of this procedure is awaited.

On comparison of primary scleral fixation of IOL with secondary scleral fixation of IOL, Lee et al. [76] found the early complications to be higher in the primary group, whereas late complications and final visual results are similar in both the groups.

As primary implantation after cataract surgery, in a patient with a small posterior capsular rupture, which ideally has been converted to a posterior continuous curvilinear capsulorhexis (PCCC) [1]. It can also be implanted secondarily in eyes which have undergone extracapsular cataract extraction without IOL implantation, in childhood or adulthood, and the capsular bag is intact and can be opened secondarily [77–79]. It can also be implanted secondarily when the edges of the posterior capsular tear have fibrosed [80].

A small posterior capsular rupture, with intact zonular support of the remainder of the capsular bag. Ideally, the posterior capsular rupture should be central or paracentral, not extending to the periphery, and should have been converted to a PCCC. Hao et al. recommended in-the-bag IOL implantation of a single-piece IOL in eyes with peripheral posterior capsular tears less than 120°, or with a central posterior capsular tear less than 4.0 mm [81].

For an in-the-bag implantation, a single-piece hydrophobic acrylic IOL is best suited, as the implantation is much more controlled. A three-piece IOL will have a greater tendency to enlarge the posterior capsular rupture, as its haptics have a greater tendency to unfold rapidly. A silicone IOL will unfold more rapidly and is less preferred than an acrylic IOL [1]. Plate-haptic IOLs should be avoided due to the risk of postoperative decentration and capsular contraction [82].

The central or paracentral posterior capsular rupture should be converted to a PCCC. A dispersive viscoelastic should be injected inside the capsular bag and posterior to the posterior capsular rupture to stabilize the posterior capsule, as the viscoelastic is not going to be aspirated and a dispersive viscoelastic has lesser tendency to raise the intraocular pressure. The IOL should be implanted in a controlled manner, so that it unfolds very slowly inside the capsular bag [37].

The bounce-back test helps in determining the stability of an IOL in the capsular bag. The IOL is gently, but deliberately, decentered, and subsequent observation of immediate recentration confirms the stability of the IOL in the capsular bag [83].

Another possible situation is the occurrence of a posterior capsular rupture while implanting a single-piece hydrophobic acrylic IOL in the capsular bag. One option is to let the IOL haptics remain behind the anterior capsular rim and prolapsing the IOL optic in front of the anterior capsular rim (reverse optic capture). This is not generally feasible with a three-piece IOL because of the posterior angulation of the haptic-optic junction [37].