Enables normal visualization of central and peripheral fundus
Requires monovision
Decreased distance visual acuity
Decreased contrast sensitivity
Perception of halos
Corneal topography changes (long-term)
Induces HOAs
Corneal haze (with long-term implantation)
Dependent on inlay centration
Dry eye
Corneal reshaping inlaysenhance near and intermediate vision through a multifocal effect, changing the shape of the anterior curvature of the cornea and making it hyper-prolate to increase power. Refractive inlaysalter the refractive index with a bifocal optic. Small aperture inlaysimprove depth of focus [9, 12].
The Raindrop™(ReVision Optics, Lake Forest, California, USA), is a reshaping inlay that is no longer commercially available. It changes the anterior corneal surface and creates a hyper-prolate region, resulting in a multifocal cornea [9, 12, 13]. In emmetropic presbyopes, the Raindrop has been shown to improve monocular and binocular UNVA [8, 14]. UIVA was also said to improve [14], however both UDVA and CDVA were found to decrease [8, 14]. It was associated with significant increases in total RMS, coma-like RMS and spherical-like RMS for a 4 mm pupil size. The Raindrop has been associated with monocular contrast sensitivity loss, but with no binocular loss. Common reasons for inlay explantation were vision dissatisfaction, inlay misalignment, decreased visual acuity, epithelial ingrowth, and recurrent central corneal haze.
The Flexivue Microlens™(Presbia Cooperatief U.A., Amsterdam, Netherlands) is a transparent hydrophilic refractive inlay (Fig. 1.1) [13, 15, 16]. Its central zone is plano and its peripheral zone has powers ranging from +1.25 to +3D for reading. A central opening facilitates the transfer of nutrients and oxygen through the cornea [ 9, 12, 13, 16, 17]. Light rays are designed to pass through the central zone during distance vision, and rays pass through the peripheral refractive zone during near vision [15, 16]. In emmetropic presbyopes the Flexivue has been found to improve UNVA [16]. UDVA is said to decrease in the operated eye, although binocular UDVA and CDVA is not significantly affected [15, 16]. Higher order aberrations [16] and mean spherical aberration [15] increased after surgery, and contrast sensitivity decreased in the operated eye [16].
Fig. 1.1
Flexivue Microlens®inlay
The Icolens™(Neoptics AG, Huenenberg, Switzerland) is a refractive inlay made of a copolymer of hydroxyethyl methacrylate and methyl methacrylate [13, 18] (Fig. 1.2). It has a bifocal design with a peripheral positive refractive zone for near and a central zone for distance vision. This implant improves UNVA, albeit with a decrease in UDVA and CDVA [18].
The Kamra Inlay™(Acufocus Inc., Irvine, CA, USA) is a small aperture inlay made of carbon nanoparticles, whose microperforations allow nutritional flow through the cornea (Fig. 1.3). It is implanted in the non-dominant eye, in a lamellar pocket. [9, 12, 13, 19] The Kamra improves near vision by increasing the depth of field through the principle of small aperture optics [9, 12, 13].
The Kamra can be implanted simultaneously with LASIK for hyperopes, myopes and emmetropes [20, 21]. Improvement in near and intermediate visual acuity have been reported [20, 21], with some compromise in uncorrected monocular distance visual acuity [22] and corrected distance visual acuity.When implanted in pseudophakic patients with monofocal IOLs—there is also improvement in NVA, and decrease in DVA [23]. Monocular contrast sensitivity is mildly reduced after implantation of the KAMRA inlay [24]. Halos, glare, and night-vision disturbance are also associated with the KAMRA [20, 21]. An advantage of Kamra inlays is their removability—with no permanent changes in corneal topography and aberrometry, and recovery of preoparative corrected and uncorrected NVA and DVA up to 6 monthsafter removal [25].
Conclusion
The idea of using intracorneal inlays to obtain multifocality is interesting, it is an active subject in ophthalmologic research. However these inlays have never gained full popularity due to issues of corneal immune reaction and centration during implantation. Other concerns that need to be addressed include late complications of corneal stromal opacity, hyperopic shift, and corneal irregularity—all of which have led to high explantation rates. As other technology for establishing multifocality is being developed, we believe that the use of these inlays will decline.
Pseudophakic Presbyopic IOL’s: Conceptual Issues and Optical Profiles
Presbyopiais the loss or insufficiency of the accommodative ability of the eye, and it causes difficulties with reading and performing tasks that require near vision. It affects individuals at the peak of their professional and creative activity, and as such, there is an increasing demand for correcting presbyopia and eliminating the need to use spectacles or contact lenses. This has been further bolstered by advances in cataract and refractive surgery and implant design.
Multifocal IOL’sprovide pseudoaccomodation—they are designed to focus light onto multiple foci and do not change power with ciliary body contraction as with accommodation [27, 28]. Bifocal IOL’sfocus light onto two discrete focal points, and trifocal IOL’sfocus light onto three focal points [27, 29, 30]. Multifocal IOL’s may also be classified according to their design. Rotationally symmetrical IOL’scan be further divided into diffractive, refractive, or combined IOL designs [27, 31]. Rotationally asymmetric or varifocal IOLsare characterized by an inferior segmental near add [32, 33]. There is a larger section for distance vision, and a smaller reading segment with only one transition zone [34]. Extended depth of focus lenses(EDOF)focus incoming light waves in a continuous and extended longitudinal plane in order to give good vision at all distances [35, 36]. Accommodative lenseshave monofocal optics which, through several mechanisms, change power with accommodative effort [37].
Several obstacles that need to be overcome by presbyopic IOL implants include visual symptoms. Glares, haloes, starbursts, dysphotopsia and shadows occur due to the effect of the lens design on light [38–40]. A large angle kappa, leading to temporal IOL decentration, has been implicated as a contributor to photic phenomena in refractive multifocal lenses [41]. Decreased contrast sensitivity is due to the splitting of available light—especially by multifocal IOLs [41]. Neuroadaptationis a phenomenon in which patients implanted with multifocal IOL implants learn to adapt to image perception changes and visual symptoms induced by the lens design. This may take several months [42]. A case series on the causes of multifocal IOL explantation and exchange reported that while uncorrected distance visual acuity may have been 20/20 or better, the visual side effects were significant enough to warrant lens exchange. The most common reasons for explantation were decreased contrast sensitivity, photic phenomena, neuroadaptation failure, incorrect IOL power, excessive preoperative expectation, IOL decentration, and anisometropia [43]. Careful preoperative evaluation and planning is also necessary for implantation of pseudophakic presbyopic implants, as lens selection should be based on a multifactorial approach. The inherent anatomy and physiology of the eye, and the pertinent ophthalmic history –especially a previous refractive surgery, irregular astigmatism, or ocular surface disease- should be considered, along with the patient’s lifestyle, visual needs, and expectations [41]. Hence a thorough knowledge and understanding of the optical qualities and profiles of each presbyopic pseudophakic lens is necessary in order to aid the surgeon in pre-operative planning and implant selection, and in advising the patient about subsequent post-operative expectations.
Optical Profiles of Presbyopic Pseudophakic Lenses
Diffractive Multifocal IOL’s
Diffractive IOLs have rings on the surface, forming a discontinued optical density, such that light particles that hit these rings are directed equally towards discrete focal points [27, 31]. Apodized diffractive IOL’s have a gradual and uniform decrease in diffractive step heights from the center to the periphery [30]. These ensure that light is equally distributed in both focal points independently of pupil size, and theoretically creates a smooth transition of light between the focal points [41]. Apodized diffractive lenseshave a gradual decrease in refractive step heights from center to periphery, resulting in distance-dominant good vision for people with large pupils [41].
The AT LISA®tri 839 MP(Carl Zeiss Meditec, Jena, Germany) is a one-piece trifocal diffractive aspheric IOL [31] (Fig. 1.4). Patients who were bilaterally implanted with the AT LISA Tri showed significant reduction in sphere, cylinder, and spherical equivalent. There was continuous and acceptable visual acuity for all distances. The defocus curves for the AT LISA tri show that it provides excellent near VA between 33 and 40 cm, with the ideal distance for near vision at 36 cm. Intermediate VA is excellent between 67 and 100 cm, and the ideal distance is at 80 cm [31]. Contrast sensitivity improved within the first month post-surgery, especially for medium spatial frequencies [31]. Ocular aberrometric analysis showed significant decrease in RMS total aberrations, RMS tilt, primary coma and RMS spherical aberration. There was a significant mean decrease in total internal aberrations. Most importantly, no significant changes were found in internal aberrations between 1, 3, and 6 months post-surgery—signifying the rapid restoration of visual function as early as the first month after surgery. The AT LISA tri induced negative values of internal spherical aberration—more negative than that previously induced by the crystalline lens—cancelling out the corneal spherical aberrations and resulting in lower ocular spherical aberration values [31].
The FineVision®Micro F(PhysIOL, Liège, Belgium) is a one-piece, pupil-dependent, trifocal IOL. It has an aspheric posterior surface, with a convoluted diffractive anterior surface (Fig. 1.5). By varying the height of the diffractive step the amount of light distributed to the near, intermediate and distant foci are adjusted according to the pupil aperture. The IOL distributes 43% of light energy to far vision, 28% to near vision, and 15% to intermediate vision [31]. Binocular defocus curve at 6 months for this lens showed a wide range of useful vision, with excellent contrast sensitivity under scotopic conditions. There was statistically insignificant reduction of HOA, yet statistically significant increase in Strehl ratio after 6 months [31].
The SeeLens(Hanita Lenses, R.C.A. Ltd., Kibbutz Hanita, Israel) is an apodized diffractive IOL with an asymmetrical light distribution. It has concentric rings located 4 mm from the the middle, and is independent of pupil size. Its design theoretically allows for an optimum distribution of energy in different light conditions and minimizes spherical aberrations [31]. Our experience with bilateral implantation of this lens in 20 patients resulted in statistically significant improvements in UDVA, CDVA, UNVA and CNVA within the first post-operative month. Mean defocus curves for the SeeLens showed that there are two peaks of maximum vision, one at distance and one at near. Defocus of −1.5D was needed to provide aceptable intermediate vision. Contrast sensitivity function was within physiologic levels, albeit reduced in scotopic conditions. Only the RMS of the internal high-order aberrations, coma aberration, third-order and fourth-order aberrations were significantly decreased. Visual qualitymeasured with the Hartmann-Shack aberrometer showed an increase in Strehl ratio [31].
Refractive Multifocal IOL’s
Refractive IOLsuse concentric zones of different dioptric powers to achieve multifocality. They are pupil dependent and may be affected by decentration, thus the number of zones that redistribute the light for distance and near vision vary [41].
The Rezoom(AMO, Santa Ana, CA) uses a refractive design which has different zones within the concentric rings for focusing at varying distances (Fig. 1.6). Studies using an eye model with a 3 mm pupil showed that its near MTF did not change in spite of decentration up to 1 mm. Clinical experience with the Rezoom has shown that it provides good distance and intermediate vision, however near vision tasks require spectacle use especially with small pupil size, and it is still associated with photic phenomena [31].
Fig. 1.6
A diagram of the Rezoom and a display of the focal points for each zone [31]
The M-Flex 630F(Rayner, East Sussex, UK) is a center distance dominant lens with five refractive zones that alternate between two powers (Fig. 1.7) [44]. Reports from clinical studies showed good monocular and binocular UIVA and UDVA, with fair UNVA. Contrast sensitivity was at par with that of monofocal IOL’s, and the incidence of visual disturbances was low. These did not change even after 12 months of follow up, and neither was there the occurrence of posterior capsular opacificationrequiring Nd:YAG laser capsulotomy [45].
Extended depth-of-focus or EDOF lenses comprise a relatively more recent class of presbyopia correcting IOL implants. These focus incoming light waves in an extended longitudinal plane and not onto discrete points as with traditional multifocal lenses. The elongated focus eliminates the overlapping of near and far images caused by traditional multifocal IOLs—improving intermediate vision while leaving far vision unaffected [35, 36, 46]. Strategies used to achieve extended depth-of-focus include the induction of spherical aberration in specific portions, the echelette design, or the use of small apertures [35]. Several of these lenses are in clinical use, and some of the new generation of multifocal IOL’s induce extended depth-of-focus to a certain extent. In 2017, the American College of Ophthalmology Task Force published a consensus statement which outlines criteria for defining an EDOF IOL and serve as a guide for appraising studies that evaluate EDOF lenses [47].
The MiniWell(SIFI, Italy) is a progressive multifocal aspheric EDOF IOL (Fig. 1.8). It has a monofocal outer zone, and the inner and middle zones have spherical aberrations with opposite signs in order to induce depth of focus and generate multifocality [48]. In vitro testing for this lens showed a comparable performance with the Symfony in terms of far and intermediate-near vision at a 3.0 mm pupil diameter [49]. HOA levels were also found to be maintained regardless of pupil size [50]. Published clinical results on the Miniwell presented good performance at intermediate. There were no relevant differences in near visual acuity between this lens and multifocal IOL’s, with few visual disturbances at night and similar contrast sensitivity as diffractive multifocal lenses [48, 51]. The personal experience of the authors, however, conflict with these results. Our own results in 10 bilaterally implanted patients have been poor near and distance vision, even requiring lens exchange. We think that this is because a huge number of patients in the reported studies so far had undergone Miniwell implantation blended with a monofocal IOL, and so it would be interesting to find large-scale studies reporting outcomes with bilateral implantation.
Fig. 1.8
A diagram of the MiniWell IOLdesign and mode of action [48]
The Wichterle Intraocular Lens-Continuous Focus(WIOL-CF; Medicem, Kemenné Zehrovice, Czech Republic) is a single haptic-less, full-optic hydrogel lens with a meniscoid anterior surface and a polyfocal hyperbolic posterior surface that creates a refractive gradient towards the optic center. This was said to be enhanced with pupil constriction during accommodative effort—making this lens both an accommodative and an EDOF lens hybrid [52]. While this lens had aceptable outcomes for UNVA and UDVA, MTF and HOA [53], it was recently withdrawn from the market [54].
Small-aperture IOL’s achieve an extended and continuous range of vision due to an embedded opaque annular mask. This mask blocks unfocused paracentral light rays and allows the entry of paraxial light rays, similar to a pinole [36, 55]. The IC-8 small-aperture IOL(Acufocus, Inc), has a 3.2 mm central mask with a 1.36 mm central aperture (Fig. 1.9). It is commercially available in Europe, Australia and New Zealand. When implanted bilaterally, an extended range of focus is attained with excellent intermediate and near vision albeit with higher scores for halos [56]. Unilateral implantation in the non-dominant eye, with micro-monovision or monovision as the target, has good near and intermediate visual outcomes, with lower halo scores and higher patient satisfaction [56, 57]. Another such device on the market is the Xtrafocus Pinhole Implant(Morcher, GmbH), which is a black hydrophobic acrylic implant (Fig. 1.10) that is placed as a piggyback lens in the ciliary sulcus. This implant has no dioptric power—it is purely a diaphragm-pinhole and its occluder has a concave-convex design to prevent contact with the primary IOL [55]. The IC-8 has demonstrated good tolerance to defocus and induced astigmatism [58]; both the IC-8 and Xtrafocus have been used for patients with highly-aberrated corneas with irregular astigmatism [59, 60]. Long-term follow-up data is pending, and would be interesting to see, for these implants.
It is important to note that there are overlaps between focality classes, and a refractive bifocal IOL may also be an EDOF IOL as well as a diffractive IOL. Some IOL’s are considered hybrids as they are designed with either diffractive or refractive surfaces with an additional design in order to induce chromatic aberrations. Other IOL’s use both diffractive and refractive technology.
The AcrySof®Restor®SN6AD3(Alcon Laboratories, Inc., Fort Worth, Texas) is a one-piece multifocal IOL that uses both apodized diffractive and refractive technology. The central 3.5 mm of the optic zone has 12 concentric steps with gradually decreasing step height. This diffractive apodized region is surrounded by the refractive area (Fig. 1.11). The Restor is an aspheric lens, and provides negative spherical aberration in order to improve contrast sensitivity. The SN6AD3 model comes with a near add of 4D, and the SN6AD1 comes with a near add of 3D for improved intermediate vision, as has been found by De Vries et al. [31, 61] Defocus curve outcomes for the SN6AD3 also show two peaks of maximal vision at far and near, with a trough for intermediate vision. Mean intraocular aberrations after implantation of the SN6AD3 resulted in higher values of total and tilt RMS compared to a monofocal IOL, while there were lower values of total, spherical and spherical-like RMS [62]. The SN6AD1 has an apodized diffractive center to focus light for near distance while the peripheral refractive zone focuses light for distance vision. Mean defocus curves for this leans shows two peaks of maximum vision for distance and near, like the SN6AD3, although an acceptable intermediate vision is maintained. Normal photopic and low mesopic contrast sensitivity was reported for both ReSTOR lenses. The SN6AD1induced lower values of spherical aberration [31].
The Panoptix®(Alcon Laboratories, Fort Worth, Texas, USA) is a single-piece, aspheric, pupil-dependent apodized IOL. This IOL has a 4.5 mm unapodized diffractive area in the center with 15 diffractive zones and an outer refractive rim. Light is then distributed to four focal points—half to the distance focus and half to the near focus. An additional feature is a negative spherical aberration on the anterior face, in order to compensate for the positive spherical aberration of the human cornea [63]. Optical bench studies of this lens showed pupil-independent good intermediate distance performance, with distance and near resolution comparable to that of a traditional multifocal IOL [64, 65]. This was in agreement with clinical studies. Furthermore, with the Panoptix there was no significant decrease in contrast sensitivity, HOA values and halo perception. Significant changeswith these results were encountered in mesopic or photopic conditions [66–68].
The Lentis®Mplus LS-313(Oculentis GmbH, Berlin, Germany) is a single-piece, refractive rotationally asymmetric, varifocal, IOL. This is a pupil-dependent IOL with an inferior surface-embedded segment (Fig. 1.12). It has two definite corrective zones for far and near vision, with a seamless transition between each zone [69]. The Lentis MPlus had significantly better CDVA than other multifocal IOL’s, and comparable UDVA and CDVA to that of a monofocal lens. Its defocus curve also showed good visual acuity from −4D to −1D. Ex vivo studies with an optical bench analysis corroborates these findings [70] There are also less reports of photic phenomena with this lens [71]. A large magnitude intraocular primary vertical coma has been reported with this lens [69], probably due to its vertically asymmetric optical geometry. This, however, confers an extended depth-of-focus which gives good vision at all distances, as evidenced by its defocus curves [69, 72]. Caution is advised, however, when measuring for higher order berrations as some machinesand measuring tools used might not accurately predict through-focus optical quality [69].
The Tecnis®Symfony(Abbot Medical Optics, Inc., Santa Ana California, USA) is a diffractive non-apodized achromatic IOL. This IOL has a biconvex wavefront-designed anterior aspheric surface and a posterior achromatic diffractive surface featuring an echelette design (Fig. 1.13) [63], thus it elongates the focus and corrects the corneal chromatic and spherical aberration [63, 73]. Ex vivo evaluation of this lens with a USAF target showed a pupil-dependent good range of vision from far to 50 cm albeit with a drop at near [74], and pupil-dependent MTF degradation [75]. Furthermore, the lens itself showed a higher absolute value of spherical aberration compared to trifocal IOL’s [74, 76]. Clinical studies found that, while bilateral implantation of Symfony resulted in good UDVA, UIVA and UNVA, better UIVA and UNVA was found when targeted for monovision [73]. When compared with other lenses- such as the Panoptix or FineVision- the other lenses had better near vision, equivalent distance vision. The Panoptix and Symfony had similar results for intermediate vision. This lens showed no statistically significant improvement in terms of light distortion, visual symptoms, contrast sensitivity and aberrometry [63, 77].
Fig. 1.13
The appearance of the concentric rings for the Symfony(a), compared with a trifocal IOL (b) and bifocal IOL (c) [74]
Accommodating IOLs
Accommodating IOLs supposedly undergo a progressive dioptric power change in response to active ciliary body contraction during an accommodative effort [78]. Several designs have been used in order to achieve the required power change but presently there is still no conclusive evidence of the targeted dioptric power change in any of the IOLs that are available or in development.
Position-changing IOL’shave a single optic which provides near and intermediate vision by anterior axial movement [37]. One such example is the CrystaLens®(Bausch & Lomb, Rochester, NY, USA), the first FDA-approved accommodating IOL, and has gone through several different designs [79]. Its optic is biaspheric to increase depth of focus, and hinges transmit ciliary body contraction to enable axial movement (Fig. 1.14). The anterior surface also changes its radius of curvature to improve near vision [80]. Significantly better UNVA was reported with the Crystalens® HD over a monofocal IOL, although there was no significant difference in CNVA. No difference was noted in intraocular aberrometric coefficient between the two lens types [80]. When compared with a low-addition-power (+1.5D) rotationally asymmetric trifocal IOL, the Lentis® M-Plus, both had comparable postoperative UNVA and CNVA. In the defocus curve, there was significantly better visual acuity with the multifocal IOL at several defocus levels. There were, however, less reports of lens tilting with the Crystalens® HD, with statistically insignificant differences in mean ocular higher order aberrations [17]. The Crystalens is, however, associated with a higher risk of posterior capsular opacity [81, 82]. Capsular contraction syndrome, or Z-syndrome, is a post-operative complication that is uniquely associated with the Crystalens®. Asymmetric capsular contraction causes the plate haptics to vault in opposite directions, inducing astigmatism [83, 84].
The 1CU®(Human Optics, Erlangen, Germany) is a single piece biconvex IOL with four flexible haptics (Fig. 1.15) that bend to allow anterior movement of the optic during accommodative effort [86]. It was discontinued due to poor near vision outcomes [87] and significant reports of glare [82]. Another single-optic lens is the TetraFlex®(Lenstec Inc, St. Petersburg, Fla, USA), which has flexible angulated closed-loop haptics (Fig. 1.16) that also allow forward movement within the capsular bag [86]. This lens has also been found to increase HOA’s within the capsular bag [88]. The BiocomFold 89A(Morcher GmbH, Sttgart, Germany) is a bag-in-the-lens implant. However, it has been found to produce limited and clinically insignificant axial movement compared to standard bag-implanted accommodating implants [89]. Other accommodating single-optic position-changing IOL’s that have been developed include the C-Well(Acuity Ltd, OrYehuda, Israel),OPAL(Bausch&Lomb, Rochester, NY, USA) andTek-Clear(Tekia, Irvine, CA, USA). There is, however, little published clinical data on these lenses [82]. The main limitation with single-optic accommodating IOL’s is that there is limited amplitude of accommodation, which is further impeded by capsular fibrosis. There are also reports of higher association with posterior capsular opacity, especially with the 1CU®—necessitating Nd:YAG capsulotomy. The YAG procedure had no effect on accommodative amplitude [82, 90].
Dual optic IOL’shave a mobile front optic connected to a stationary rear optic by a spring-type haptic [86]. The now-discontinued Synchrony®(Visiogen Inc, Abbott Medical Optics, Santa Ana, California, USA) had an anterior biconvex optic with a high plus power and a posterior concave optic with a low minus power (Fig. 1.17). Tension caused by the capsular bag compresses the optics and an attempt to accommodate releases this strain energy [81, 91]. The Synchrony®has similar outcomes as the Crystalens® HD—with no statistically significant differences in UDVA, CDVA, near or intermediate visual outcomes between the 2 IOLs [81]. The Sarfarazi(Bausch & Lomb, Rochester, NY, USA) has 2 optic lenses connected by three haptics (Fig. 1.18). The change in dioptric power is also brought about by the displacement of the anterior optic. Ex vivo testing has shown that this is capable of attaining an amplitude of accommodation of up to 4.0D [82]. This lens has never been released commercially and there is no published paper on its clinical results.
Dual-optic lenses, specifically the Synchrony Lens, completely occupy the capsular bag, leading to a lower incidence of PCO. This also theoretically facilitates lens movement during accommodative effort and has been clinically shown with a wider range of defocus curves compared to single-optic lenses [81]. Studies have shown that there is no reduction in accommodative ability over a year-long follow-up period [92], and so it would be interesting to see long-term results with these lenses. While dual-optic accommodating IOL’s have significantly better ocular quality than single-optic lenses, with comparable distance-vision outcomes, their near-vision outcomes are still limited [81] and patients may require training in order to attain good visual performance [92]. Yet another significant finding with dual-optic lenses is magnification of the viewed image, because of the increased distance between the retina and the image space nodal point during accommodative effort and movement of the anterior lens [93].
Shape-changing IOL’scan change lens curvature to change dioptric power. The FluidVision®(Powervision, Belmont, California, USA) has optics filled with silicone oil. During accommodation, this oil is pushed into the optic through fluid channels that connect the haptics to the optic, inflating the lens and increasing the dioptric power for near vision [94]. The NuLens®(DynaCurve, Herzliya Pituah, Israel) is a conceptual sulcus-implanted lens that consists of PMMA haptics, a PMMA anterior reference plane that provides distance vision correction, a small chamber that contains a solid silicone gel, and a posterior piston with an aperture in the center (Fig. 1.19). When pressure is applied on the posterior piston, the gel-filled chamber bulges to increase or decrease optical power [95]. The Juvene accommodating IOL(LensGen, Irvine, CA) is a 2-component IOL with a fixed foldable lens—consisting of a base optic similar to that of an aspheric monofocal lens and a 360-degree haptic (Fig. 1.20). The foldable lens is injected through a 3.2 mm incision after which another fluid-based shape-changing lens is inserted and secured to the first with 3 tabs. The fluid lens has a flexible anterior suface which can change curvature in response to capsular forces with accommodation [52]. Clinical trialsinvolving this lens are anticipated to start soon, and these would be interesting to see.
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