The IOL for Visually Impaired People (IOL-VIP) System
The classic IOL-VIP system (Fig. 1 and Table 1) is a double IOL implant for the visual rehabilitation of patients with macular disease. It consists of a biconcave high-minus-power IOL in the capsular bag and a biconvex high-plus-power IOL in the anterior chamber, creating, together with the cornea, an intraocular Galilean telescope with ×1.3 magnification for distance .In a group of 40 eyes of 35 patients, this lens system was reported to be effective and well tolerated. It improved best-corrected visual acuity (BCVA), reading magnification, and reading distance . The software provided with the IOL-VIP system can be used to estimate preferred retinal locus (PRL), reading speed, contrast sensitivity, and visual acuity . It can also be used for training the PRL pre- and postoperatively and can enable the detection of >66% of patients whose PRL may be too far from the fovea and/or who are not responding adequately to pre-surgical training, decreasing the risk for implant removal . However, fixation and focusing of the device on one PRL during the course of training may limit future performance as the disease progresses and PRL changes.
Clinical results for the IOL-VIP system indicate that it is well tolerated and does not interfere with peripheral or binocular vision . This system also has significant limitations that include a need for perfect alignment between the two IOLs and the need for a relatively large (up to 7 mm) corneal incision for insertion. Adverse events associated with the IOL-VIP system include transient elevations in intraocular pressure (IOP), corneal edema, ocular pain, posterior capsule opacification, pupillary block, and anterior capsule fibrosis [4, 12,13,14]. The large incision may result in induced astigmatism and challenges with wound healing in the postoperative period. Other potential limitations for this system include a possible crowding effect with two lenses, particularly with one IOL in the anterior chamber that may increase the risk for glaucoma or angle closure, especially in patients with hyperopia . Furthermore, the magnification is limited to ×1.3, and long periods of pre- and postoperative adaptation are required for the IOL-VIP, which may not be acceptable for some patients .
The IOL-AMD (Fig. 2 and Table 1) uses the principle of the Galilean telescope (with the cornea) to produce ×1.25–×1.3 magnification with a visual field reduction of about 30% . After the removal of the crystalline lens or existing IOL, one high-negative and one high-positive soft hydrophobic IOLs are injected individually into the capsular bag and ciliary sulcus, respectively, using 3-mm corneal incisions . Results from 18 eyes of 12 patients indicated no significant intra- or postoperative complications and improvement in mean decimal corrected distance visual acuity (CDVA) from 0.12 preoperatively to 0.20 at 4 months. The mean change in spherical equivalent was 1.5 dioptres (D) with 0.5 D of induced astigmatism. Microperimetric testing in a subset of three patients indicated a magnification effect and a deviation of the retinal image by up to 5 degrees, with improved fixation stability . Complications associated with this device included IOP elevation and anterior vaulting of the IOL in the capsular bag in one patient, which resulted in a decrease in visual quality . An important advantage of this lens is a uniform breadth of focus across the macula because of traverse asphericity . However, this approach also has some limitations, including a magnification that extends only to ×1.3. Moreover, further progression of AMD may require additional surgery due to the associated change in PRL . Importantly, the normal range of daily activities typically requires multiple PRLs, and limiting the PRL to one area could cause further visual dysfunction. Because of these limitations, the manufacturing of the device has been discontinued .
This is a single-piece, soft, hydrophobic acrylic IOL, comparable to a standard IOL in terms of dimensions (6–13 mm) (Fig. 3 and Table 1). It improves image quality across the entire macula, increasing the breadth of focus and reducing blur. The optics of this lens are wavefront optimized with the aim of providing improved image quality for an area extending about 10 degrees from the center of the fovea . It permits patients with single or multiple PRLs to gain optimum benefit from the most functional areas of their macula  and provides magnification from ×1.1 to ×1.2 . EyeMax Mono is available in two versions: the first is engineered for capsular bag implantation following phacoemulsification, and the second is employed for sulcus implantation and use in combination with a previously implanted monofocal IOL . Results from a consecutive case series of 244 eyes with dry or stable wet AMD and logMAR visual acuity ≥0.3 indicated a mean CDVA (logMAR) improvement from 1.06 preoperatively to 0.71 postoperatively . Mean preoperative corrected near visual acuity (CNVA, logMAR) increased from 1.36 to 0.88 . Complications associated with the implantation of the EyeMax Mono included anterior capsular tear, postoperative subretinal fluid, and elevated IOP . As other authors have acknowledged, more information is needed about the efficacy, safety, and functional outcomes achieved with this lens .
The first Lipschitz macular implant (LMI) (Fig. 4 and Table 1) was an IOL that used the principle of the Cassegrain mirror reflecting telescope [11, 18, 19]. Dielectric coatings on the LMI act as mirrors to produce a ×2.5 magnified image centrally on the retina and a regular-sized image in the periphery . Results from six eyes of six patients (four with AMD and one each with myopic macular degeneration or macular dystrophy) indicated a mean gain in distance acuity of 3.66 lines and a mean increase in the Early Treatment Diabetic Retinopathy Study (ETDRS) score for near acuity of 50.83 logMAR .
Advantages of the LMI include the provision of ×2.5 magnification and the fact that a newer version of this device can be directly implanted in the sulcus (LMI-SI) . Limitations associated with this lens include the fact that the LMI-SI, which is a non-foldable, one-piece IOL, requires enlarging incisions to as much as 5.5 mm . In addition, all patients implanted with this lens experienced glare postoperatively, and two patients complained of shadowing which resolved by 3 months [18, 19].
Bulb miniature lenses
The Scharioth Macula Lens (A45SML) is a single-piece lens developed for the visual rehabilitation of patients with advanced AMD (Fig. 5 and Table 1) . It is a macular add-on IOL developed for ciliary sulcus implantation in pseudophakic eyes and can be implanted during uncomplicated standard phacoemulsification with in-the-bag posterior chamber IOL implantation, or years after cataract surgery . The lens has a central portion of 1.5 mm diameter with addition of +10 D. The magnification is ~×2.0 for very near vision only when calculated mathematically, but in practice depends on both the anatomy of the eye and the final reading distance. The overall diameter of the IOL is 13.0 mm with four symmetric haptics .
Results from a prospective multicenter trial that included 50 eyes of 50 pseudophakic patients with either dry or previously treated wet AMD that was stable for ≥6 months showed a mean CNVA improvement from 0.23 preoperatively to 0.57 at 1 year postoperatively. The mean preoperative CDVA was 0.19, which did not change postoperatively. One patient had the lens explanted 3 months postoperatively due to glare/halos .
This lens has multiple advantages. It is designed to enhance near vision only with reduced reading distance and maximum magnification, without affecting or enhancing peripheral vision [11, 19]. It is also one of the few lenses that can be implanted as part of routine cataract surgery as well as in pseudophakic patients, and only a small incision (2.2 mm) is required for implantation [11, 21]. Limitations of the A45SML include the fact that it is contraindicated in patients with other eye conditions including chronic uveitis, zonular weakness, secondary cataracts, and central corneal opacities . Notably, magnification of objects is possible only when they are within 10–15 cm of the eye .
LENTIS MAX is a monofocal, hydrophobic, acrylic, aspheric IOL that enables a ×3 magnification at a distance of 15 cm [23, 24]. This biconvex lens with the aspherical surface that has two sectors with a total additional power of +8 dioptres  (Fig. 6). It has been employed for magnifying cataract surgery (MAGS) in 15 patients with advanced dry AMD. Eleven of these patients were followed for up to 48 months and all reported functional gains in the first 3–6 months after surgery. In addition, 10 of the 11 patients reported improved quality of life . Other benefits include a routine procedure that does not introduce additional risks, as the lens has standard dimensions. These lenses are not available at present due to a calcification-related recall of another lens produced by the company .
Implantable miniature telescope prosthesis
The IMT was invented by Isaac Lipschitz and is based on the principle of fixed-focus Galilean telescopes [11, 19]. The IMT is designed from ultraprecision quartz glass and wide-angle micro-optics (Fig. 7 and Table 1) . Together with the cornea, the IMT telephoto effect enlarges objects in the central visual field . Because the device is implanted only in one eye, peripheral vision is compensated by the fellow eye [11, 27]. The IMT is available in two wide-angle magnifications (×2.2 and ×2.7) and requires approximately 10- to 11-mm incision for implantation [19, 28, 29]. It was first evaluated in a phase 1 trial that included 14 patients ≥60 years of age with bilateral GA or disciform scar AMD and cataract. At 12 months, 77% of 13 patients gained ≥2 lines of either distance or near BCVA, and 62% gained ≥3 lines; scores for activities of daily living (ADLs) improved for all patients .
The efficacy and safety of the IMT have been confirmed in a 1-year study with an additional 1 year of follow-up that included 217 patients with AMD and moderate-to-profound bilateral central visual acuity loss resulting from GA, disciform scar, or both [29, 30]. At 2 years, 59.5% of 173 telescope-implanted eyes gained ≥3 lines of BCVA compared with 10.3% of 174 fellow eyes . Mean BCVA improved by 3.6 lines and 2.8 lines from baseline in eyes with the ×3 (nominally ×2.7) and ×2.2 lenses, respectively. Most patients also had sustained improvements in the ability to carry out ADLs . Five-year follow-up of these patients indicated retention or improvement in best CDVA and corneal endothelial cell density (ECD) loss consistent with that reported for conventional IOLs . This lens has been approved by the United States Food and Drug Administration (FDA) for implantation in patients ≥65 years who have a natural lens in at least one eye and who meet other criteria for health and overall vision . It has also received the Conformité Européenne mark for the treatment of end-stage AMD . Moreover, it is worth noting that treatment with this lens has been shown to be cost-effective, with a very low cost per quality of life-year gained .
It is worth emphasizing that the placement of IMT does not interfere with standard monitoring (e.g., with ocular coherence tomography) ; or with adjunctive treatments such as administration of intravitreal injections , laser photocoagulation , laser-assisted cataract surgery  or pars plana posterior capsulotomy .
The Smaller-Incision New-Generation IMT
The Smaller-Incision New-Generation IMT (SING IMT) (Fig. 8 and Table 1) is a newer version of IMT designed with a pre-loaded delivery system. It requires a 6.5-mm incision, and surgery time is less than 30 min . The smaller incision size with the SING IMT also significantly reduces surgical trauma, induced astigmatism, the number of sutures required, and loss of ECD, which permits more rapid initiation of rehabilitation [4, 37]. Both IMT and SING IMT have similar magnification ranges (×2.2 and ×2.7 nominal, respectively)  and aid vision at near, mid, and far-range distances. Other similarities and differences between the IMT and SING IMT are summarized in Table 2 .