Historical Background

In 1964 Barraquer developed keratophakia, a lamellar refractive procedure in which an alloplastic lenticule is placed at the interface of the free corneal cap and the stromal bed. The difficulty of the surgical procedure and the unpredictability of the refractive results meant that few surgeons adopted keratophakia.

Early corneal implants were made of polymethylmethacrylate or polysulfone, and although they corrected the refractive error, they produced corneal necrosis and implant extrusion. Nowadays, the material used in corneal inlays allow sufficient nutrient flow; a very important feature because interruption of the nutrient flow can cause loss of transparency, corneal thinning, epithelial and stromal decompensation, and melting. The permeability of the hydrogel material used in the inlays is similar to that of the corneal stroma, allowing to some extent the exchange of nutrients such as glucose and oxygen.

Corneal inlays have several advantages: There is no need to remove corneal tissue, the surgical technique is relatively easy and minimally invasive, and the inlays are all removable.

There are three types of corneal inlays :

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  Corneal reshaping inlays

  
  
  
  
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    They enhance near and intermediate vision through a multifocal effect. There’s a reshape of the anterior curvature of the cornea (hyperprolate region of increased power).

  
  
  
  
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  Refractive inlays

  
  
  
  
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    An alteration of the refractive index occurs with a bifocal optic.

  
  
  
  
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  Small aperture inlays

  
  
  
  
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    There is an improvement of depth of focus.

  
  

The inlays are implanted in the nondominant eye within a corneal pocket made by a femtosecond laser or under a stromal flap (the pocket is preferred because it might decrease the incidence of dry eye). The depth depends on the inlay. Inlays that alter the curvature of the cornea are implanted more superficially; inlays with small aperture or those that have a different index of refraction are implanted deeper to avoid changes in the cornea curvature and to allow a proper diffusion of nutrients in the corneal stroma. The inlays must be centered on the first Purkinje reflex.

There are currently four corneal inlays available on the market:

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  KAMRA Vision (AcuFocus Inc., Irvine, CA, USA). Small aperture inlay.

  
  
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  Raindrop (ReVision Optics Inc., Lake Forest, CA, USA). Corneal reshaping inlay.

  
  
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  Flexivue Microlens (Presbia Cooperatief U.A., Amsterdam, the Netherlands). Refractive inlay.

  
  
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  Icolens (Neoptics AG, Hünenberg, Switzerland). Refractive inlay.

Raindrop

Formerly known as the PresbyLens or Vue + lens (ReVision Optics, Lake Forest, CA, USA), it’s made of biocompatible hydrogel material and 80% water. It has a thickness of 10 µm at the periphery and 32 µm at the center; the diameter is 2 mm ( Fig. 3.10.2 ). The inlay is permeable, allowing the passage of nutrients and oxygen. It reshapes the anterior central corneal surface, creating a hyperprolate region, resulting in a multifocal cornea. It has no refractive power.

Raindrop corneal inlay.

It should be placed in the nondominant eye at a minimum depth of 150 µm with a residual stromal bed thickness of 300 µm and has to be aligned over the center of the light-constricted pupil. The central corneal thickness of the eye should be 500 µm or thicker. After the inlay is positioned over the center of the pupil, it has to dry for 30 seconds before the flap is repositioned.

Barragan et al. reported the results of a 1-year follow up using the Raindrop inlay in emmetropic presbyopes. In their study, 100% of eyes achieved an uncorrected near visual acuity (UNVA) of 0.2 logMAR or better in the operative eye, and binocularly, 100% of patients achieved an UNVA of 0.18 logMAR or better. No eye lost two or more lines of corrected distance visual acuity (CDVA) or corrected near visual acuity (CNVA).

Yoo et al. measured the corneal and optical aberrations in 22 emmetropic presbyopes with a mean addition power of +1.97 ± 0.30 D. All patients gained monocular and binocular UNVA. For a 4-mm pupil size, significant increases occurred in total root mean square (RMS), coma-like RMS, and spherical-like RMS. Overall, 82% of the patients were satisfied or very satisfied with their near vision, and 13.6% reported that they needed glasses for near vision more often after surgery than before surgery. Moreover, 37% of patients reported glare. They concluded that the procedure can induce higher-order aberrations (HOA) but had moderate effects on the entire optical system.

In a study by Alió et al., increases in spherical aberrations, coma, and total HOA were reported with the implantation of hydrogel inlays.

Whitman et al. reported the clinical outcomes with the Raindrop inlay in patients with emmetropic presbyopia. In total, 340 patients completed a 1-year follow-up, and on average, they had an improvement in UNVA of five lines and in uncorrected intermediate visual acuity (UIVA) of 2.5 lines. However, the uncorrected distance visual acuity (UDVA) decreased by 1.2 lines. Contrast sensitivity loss occurred at the highest spatial frequencies with no loss of binocularly. Eighteen inlays were replaced because of decentration, and 11 were explanted (five patients were dissatisfied with their vision, two had inlay misalignment, two had epithelial ingrowth, one had visual symptoms associated with decreased visual acuity, and 1 had recurrent central corneal haze that failed to respond to topical treatment).

Presbia Flexivue Microlens

The Presvia Flexivue Microlens, a transparent hydrophilic concave–convex disc made of a clear copolymer of hydroxyethylmethacrylate and methylmethacrylate with an ultraviolet blocker. It has a diameter of 3.2 mm and a thickness of 15–20 µm, depending on the additional power. The central 1.8 mm diameter of the disc is plano in power, and the peripheral zone has an add power, ranging from +1.25 D–3.00 D in 0.25-D increments. At the center, there is an opening of 0.15 mm that facilitates the transfer of nutrients and oxygen through the cornea ( Fig. 3.10.3 ). It has a refractive power of 1.4583 and a light transmission of 95% at a wavelength above 410 nm.

Flexivue Inlay.

(Image from Malandrini A, Martone G, Menabuoni L. Bifocal refractive corneal inlay implantation to improve near vision in emmetropic presbyopic patients. J Cataract Refract Surg 2015;41:1962–72.)

During distance vision, light rays pass through the central zone of the inlay that does not have refractive power (plano), so they will be sharply focused on the retina. Light rays that pass through the refractive peripheral zone will focus in front of the retina.

During near vision, rays passing through the central zone of the inlay will focus behind the retina, and those passing through the peripheral refractive zone of the inlay will be focused on the retina. The rays passing through the peripheral clear cornea will be blocked by the pupil.

It is implanted in the nondominant eye. The corneal pocket is within a depth of 280–300 µm and is centered over the patient’s visual axis based on the first Purkinje reflex. The corneal inlay power is calculated by decreasing the preoperative CNVA manifest refraction SE by 0.25 D.

Limnopoulou et al. reported in their 1-year follow-up study a UNVA of 20/32 or better in 75% of operated eyes; the UDVA decreased significantly in the operated eye from 20/20 to 20/50, but binocular UDVA was not significantly altered. HOA increased and contrast sensitivity decreased in the operated eye. They included 47 emmetropic presbyopes between 45 and 60 years old. No removals of the inlay and no intra- or postoperative complications occurred.

Malandrini et al. performed a 36-month follow-up study in 26 eyes, and the mean preoperative UNVA and UDVA were 0.76 logMAR and 0.00 logMAR, respectively, compared with 0.10 logMAR and 0.15 logMAR, postoperatively. Overall, 62% of the eyes lost more than 1 line of UDVA, and 19% lost more than two lines of UDVA. Also, 8% of the eyes lost more than 1 line of CDVA at 36 months. The mean spherical aberration increased after surgery. Explantation was performed in six eyes because of reduced UDVA, halos, and glare; 6 months after explantation, the CDVA in all cases had returned to preoperative levels.

Icolens (Neoptics AG)

This corneal inlay is made of a copolymer of hydroxyethyl methacrylate and methyl methacrylate. It has a bifocal design with a peripheral positive refractive zone for near vision and a central zone for distance vision. It has a diameter of 3 mm, a peripheral thickness of 15 µm, and a central 0.15 mm hole for nutrient flow ( Fig. 3.10.4 ).

Icolens Inlay.

(Image taken from Baily C, Kohnen T, O’Keefe M. Preloaded refractive-addition corneal inlay to compensate for presbyopia implanted using a femtosecond laser: one-year visual outcomes and safety. J Cataract Refract Surg 2014;40:1341–8.)

Baily et al. reported the results of the Icolens 12 months after implantation. The inlay was implanted in the nondominant eye of emmetropic patients through a corneal pocket created by femtosecond laser at a depth of 290 µm; 52 patients were included. The UNVA improved from N18/N24 preoperatively to N8 postoperatively, with 100% of patients having N16 or better, and nine patients having N5 or better. The mean UDVA in the surgical eye worsened significantly from 0.05±0.12 logMAR preoperatively to 0.22±0.15 logMAR postoperatively. There was a loss of CDVA, with 77% of the patients losing more than one line (they believe this was secondary to a neuro-optical phenomenon related to the implant). Seven inlays were removed because of inadequate centration, three secondary to ambiguous ocular dominance, and one because the patient had unrealistic expectation, for a total of 11 inlays removed.

KAMRA

The KAMRA inlay (AcuFocus Inc., Irvine, CA, USA) is the most widely used corneal inlay, with nearly 20,000 inlays implanted worldwide. It is made of polyvinylidene fluoride. The latest design (ACI 7000PDT) has a 3.8-mm diameter with a central 1.6-mm aperture and a thickness of 5 µm. It has 8400 microperforations ranging in diameter from 5 to 11 µm to allow nutritional flow through the cornea. It also has nanoparticles of carbon, which has a light transmission of 5%. Because it is an opaque inlay, it may be visible in light-colored eyes ( Fig. 3.10.5 ).

KAMRA Inlay in a Light-Colored Eye.

(Image taken from Abbouda A, Javaloy J, Alió JL. Confocal microscopy evaluation of the corneal response following AcuFocus KAMRA inlay implantation. J Refract Surg 2014;30:172–8.)

The KAMRA inlay improves near vision by increasing the depth of focus through the principle of small aperture optics. It is implanted in the nondominant eye in a lamellar pocket that is 200–220 µm. Its implantation does not cause scotomas in the visual field. It allows a normal visualization of the central and peripheral fundus and a good quality of central and peripheral imaging and optical coherence tomography (OCT) scans. However, annular shadows visible on the GDx VCC scans have been reported.

The inlay has evolved over the years, with the same artificial aperture of 3.8-mm outer diameter and 1.6-mm inner diameter. Table 3.10.2 describes the inlay characteristics.

Tomita et al. evaluated the outcomes of KAMRA inlay implantation and simultaneous LASIK in hyperopic, myopic, and emmetropic patients. With a 6-month follow-up, they concluded that the procedure was safe and improved distance and near visual acuity. However, postoperative symptoms like halos, glare, and night-vision disturbances were observed.

Igras et al. reported a 1-year follow-up of combined LASIK and KAMRA inlay implantation. Of 132 patients evaluated, 85% were hypermetropic, 11% emmetropic, and 4% myopic. By 12 months, 97% of patients had J3 or better UNVA. Also, 6.3% of patients lost one line of CDVA in the implanted eye, and none lost two or more lines compared with their preoperative VA. Two inlays were explanted, one due to poor night vision and one secondary to persistent hyperopic shift and corneal haze. They concluded that a significant improvement occurred in near visual acuity with a slight compromise in uncorrected monocular distance visual acuity in the implanted eye without a binocular effect on the UDVA.

Seyeddain et al. performed a 3-year follow-up with 32 emmetropic presbyopic patients and reported that although there were significant gains in UNVA and UIVA, 28.3% of patients lost one line of CDVA.

Dexl et al. described iron corneal deposits after implantation of the AcuFocus corneal inlay (ACI 7000) in 18 eyes (56%), but these deposits did not have any influence on distance, near, uncorrected, or corrected visual acuity ( Fig. 3.10.6 ).

Iron Deposits in the Periphery on the Inlay (Red Arrows) and in the Center of the Inlay (Green Arrow).

(Image taken from Dexl AK, Ruckhofer J, Riha W, et al. Central and peripheral corneal iron deposits after implantation of a small-aperture corneal inlay for correction of presbyopia. J Refract Surg 2011;27;876–80.)

Alió et al. reported that after removal of the KAMRA inlay, the topography and aberrometry were not permanently affected, and more than 60% of the patients had a CNVA, CDVA, UNVA, and UDVA similar to their preoperative values. The study involved 10 eyes and had a follow-up of 6 months after the inlay removal. The reason for removal in eight eyes was subjective dissatisfaction with visual symptoms (glare, starburst, blurry vision, and halos). One case was related to an inadvertent thin flap, and the other was related to insufficient near vision.

Abbouda et al. analyzed the corneal tissue appearance 6 months after KAMRA inlay implantation by confocal microscopy; the study included 12 eyes in which one of three models of the KAMRA inlay had been implanted. The epithelial layers appeared normal in all patients. A low grade of keratocyte activation was found in all patients. Few patients had an elevated number of activated keratocytes, and they had a reduction in UNVA (needed reading glasses), CNVA, and CDVA. The UDVA was not affected. Subbasal nerve plexus was detected in 10 patients, and the branch pattern was found in eight patients. Four patients had the inlay explanted, the main reason being subjective dissatisfaction with visual symptoms and poor vision. All of them had a donut appearance at the slit-lamp examination. None of the patients had refractive postoperative changes. They concluded that the corneal tolerance to the inlay is good and that it modifies the normal structure of the corneal layer without associated complications.

Keratocyte activation is an important variable for the refractive outcome after KAMRA inlay implantation; flap thickness depth, low laser energy cut, and topical corticosteriod treatment are helpful to avoid it.

Lin et al. compared the contrast sensitivity before and after implantation of the KAMRA inlay in 507 patients. They reported that postoperatively contrast sensitivity was mildly reduced monocularly but not binocularly, and that it remained within the normative ranges.

This inlay can be implanted also in patients with previous cataract surgery who have a monofocal IOL, as reported by Huseynova et al. They implanted the KAMRA inlay in 13 pseudo-phakic patients with a monofocal IOL. Four patients had LASIK at the time of the inlay implantation. There was no change in mean UDVA after the inlay implantation, and the mean UNVA improved by five lines. Three eyes lost two lines, and one eye lost one line of UDVA. Two eyes lost two lines, and one eye lost one line of CDVA ( Table 3.10.3 , Table 3.10.4 , Fig. 3.10.7 ).

Corneal Approach of Presbyopia.

Rotationally Symmetrical

Rotationally Asymmetrical IOLs (Varifocal)

These are characterized by an inferior segmental near add. The IOL has a larger section for distance vision and a smaller reading segment, with only one transition zone. The near add varies from +1.5 D to +3.00 D, depending on the patient’s visual needs.

Patient Selection Criteria

Adequate patient selection is the most important part in implanting a multifocal IOL. We must know the patient’s visual expectations and make sure that we can fulfill them by selection of the correct IOL, because depending on the IOL design, the patient can have better near or intermediate distance vision. Also, patients’ expectations have to be realistic, and we have to inform them of the visual side effects that they may experience with the multifocal IOLs (glare, halos) and that a process of neuroadaptation exists that takes a couple of months.

The correct IOL power calculation is crucial, and emmetropia should be the target. It has been reported that the cause of 20% of cases of multifocal IOL explantation is incorrect IOL power.

Astigmatism correction is mandatory for a good performance of the multifocal IOL. Patients with irregular astigmatism are not good candidates for a multifocal IOL because its correction is not easy or predictable.

Patients with corneal abnormalities like central scars and Fuchs’ dystrophy are not suitable candidates for multifocal IOL implantation.

Because many of the multifocal IOLs are pupil dependent, an adequate function before and after surgery is needed. Therefore, if a patient has a very small pupil diameter that needs surgical manipulation, the surgeon should be very careful to not damage the iris sphincter. Patients with larger pupils may experience glare and halos after multifocal IOL implantation. Identification of zonular weakness during surgery is very important, as decentration or tilt of the multifocal IOL can have a detrimental effect on the visual acuity. This can be prevented by the implantation of a capsular tension ring.

Any macular alteration must be recognized before implantation of a multifocal IOL, especially if the patient has these predisposing factors: male gender, former or current smoker, and history of heart disease. A macular disease is a relative contraindication for the implantation of a multifocal IOL because these patients have a reduced contrast sensibility that can be worsened by a multifocal IOL. Thus the macula should be evaluated with either a macular function test or OCT.

Retinal diseases like Stargardt and retinitis pigmentosa are absolute contraindications for multifocal IOL implantation. Other diseases like diabetic retinopathy, macular degeneration, and epiretinal membranes have a decreased contrast sensitivity that may be worsened by the multifocal IOL. Glaucoma is a relative contraindication for the use of multifocal IOLs. If the patient has an early glaucoma or controlled ocular hypertension, a multifocal IOL can be implanted, but IOL implantation should be avoided in patients with progressive and advanced glaucoma.

There are many multifocal IOLs available on the market; we will discuss the most popular ones.

AcrySof Restor SN6AD3 (Alcon Laboratories, Inc.)

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  Apodized diffractive and refractive technologies

  
  
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  Type: One-piece multifocal IOL

  
  
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  Material: hydrophobic acrylic

  
  
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  Filter: UV and blue light

  
  
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  Pupil dependent: No

  
  
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  Optic diameter: 6 mm

  
  
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  Overall diameter: 13 mm

  
  
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  Refractive index: 1.47

  
  
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  Power range: +6.00 to +34.00 D

  
  
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  Near addition at lens plane: +4.00 D

  
  
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  Incision size: >2.2 mm

The central 3.5 mm of the optic zone has 12 concentric steps of gradually decreasing (1.3–1.2) step heights. Surrounding this apodized region is the refractive area that directs light to a distance focal point for large pupil diameters.

In bright light with constricted pupils, the lens sends light energy to near and distant focal points; in low light with dilated pupils, the apodized diffractive lens sends a greater amount of energy to distance vision to minimize visual disturbances ( Fig. 3.10.8 ).

AcrySof Restor SN6AD3.

(Image from Alió J, Pikkel J. Multifocal intraocular lenses. The art and the practice. 1st ed. Editorial Springer; Switzerland 2014.)

Symfony (Abbott Medical Optics, Inc.)

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  Type: diffractive nonapodized achromatic

  
  
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  Material: UV-blocking hydrophobic acrylic

  
  
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  Optic diameter: 6 mm

  
  
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  Overall diameter: 13 mm

  
  
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  Power range: +5.00 D to +34.00 D in 0.50 D increments

  
  
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  Refractive index: 1.47

It has a biconvex wavefront-designed anterior aspherical surface and a posterior achromatic diffractive surface ( Fig. 3.10.10 ).

TECNIS Symfony IOL.

(Image from http://eyewiretoday.com/news.asp?t=474 .)

This IOL elongates the focus and corrects the corneal chromatic and spherical aberration using an achromatic technology also known as “extended range of vision.”

The chromatic aberrations have a detrimental effect on vision because they reduce contrast vision and induce blur.

The improvement of both aberrations increases the retinal image quality with a better tolerance of decentration and without sacrificing the depth of field.

It provides better near, intermediate, and distance vision than aspherical monofocal IOLs, and in contrast to multifocal IOLs, it does not induce aberrations to extend the depth of focus.

Because it provides an elongated focal area rather than various focal points, halos are not as common as with the multifocal IOLs. In fact, one study reported that 90% of patients in whom a Symfony IOL was implanted reported no or mild halos or photic phenomena, and the visual results were better than those obtained with a rotationally asymmetrical multifocal IOL or an apodized diffractive IOL.

AT LISA tri 839 MP (Carl Zeiss Meditec AG)

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  Type: one-piece trifocal diffractive aspherical IOL

  
  
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  Material: hydrophilic acrylic 25% with hydrophobic surface

  
  
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  Optic diameter: 6 mm

  
  
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  Overall diameter: 11 mm

  
  
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  Power range: from plano to +32.00 D in 0.5 D increments

  
  
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  Near addition at the IOL plane: +3.33 D for near vision, +1.66 D for intermediate vision

  
  
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  Incision size: 1.8 mm.

  
  
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  Asphericity: −0.18 µm.

The central 4.34 mm of the IOL optic is the trifocal zone, and the peripheral bifocal zone is from 4.34 to 6 mm with diffractive rings covering the entire optic diameter ( Fig. 3.10.11 ).

AT LISA Tri 839 mp IOL.

(Image from Alió J, Pikkel J. Multifocal intraocular lenses. The art and the practice. 1st ed. Editorial Springer; Switzerland 2014.)

Fine Vision Micro F (Physiol)

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  Type: one-piece trifocal

  
  
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  Optic: diffractive anterior surface, aspherical posterior surface

  
  
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  Material: 25% hydrophilic acrylic

  
  
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  Optic diameter: 6.15 mm

  
  
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  Overall diameter: 10.75 mm

  
  
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  Power range: +10.00 D to +35.00 D in 0.5 D increments

  
  
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  Near addition at spectacle plane: +1.75 D intermediate vision, +3.5 D near vision

  
  
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  Incision size: >1.8 mm

  
  
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  Asphericity: −0.11 µm

  
  
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  Pupil-dependent IOL

FineVision Micro F IOL.

(Image from Alió J, Pikkel J. Multifocal intraocular lenses. The art and the practice. 1st ed. Editorial Springer; Switzerland 2014.)

Panoptix (Alcon)

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  Type: one piece, aspherical

  
  
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  Material: hydrophobic, ultraviolet- and blue light–filtering acrylate/methacrylate copolymer

  
  
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  Optic diameter: 6.0 mm

  
  
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  Overall diameter: 13.0 mm

It has a 4.5-mm diffractive area in the center with 15 diffractive zones and an outer refractive rim ( Fig. 3.10.13 ).

Panoptix IOL.

(Image from Kohnen T. First implantation of a diffractive quadrafocal (trifocal) intraocular lens. J Cataract Refract Surg 2015;41:2330–2.)

Light distribution is 25% to near (40 cm), 25% to intermediate (60 cm), and 50% to distance vision.

There is a more physiological transition from different distances because of an advanced optical technology, so the light from the first focal point is diffracted to the distance focus. This helps to create a fourth focal point at 1.20 m, making this IOL a quadrafocal IOL, although it acts as a trifocal IOL.

Based on laboratory simulations, the performances in image quality, photic phenomena, and resolution are equivalent between the Panoptix IOL and the AT LISA tri 839MP and FineVision Micro F trifocal IOL.

Clinical Outcomes and Quality of Life

Carballo-Alvarez et al. evaluated visual outcomes 3 months after bilateral implantation of the FineVision trifocal IOL. They reported adequate near, intermediate, and far vision, with satisfactory contrast sensitivity and no significant photic phenomena.

A comparison between the FineVision trifocal and the Restor IOL reported similar refractive outcomes, reading speeds, and patient satisfaction, although the intermediate distance in the defocus curve was better in the trifocal IOL group. Spectacle independence was achieved in 80% of the patients with the trifocal IOL and in 50% of the patients with the bifocal IOL.

Similar outcomes were reported by a study comparing the Restor IOL with the AT LISA tri. The latter gave better intermediate visual acuity, whereas near and distance visual acuity were good with both IOLs. The Quality of Vision questionnaire showed similar visual disturbances between the two groups.

A comparison of the visual outcomes and intraocular optical quality between the Lentis Mplus and the Restor IOL reported that the UNVA and distance-corrected near visual acuity (DCNVA) were better with the Lentis Mplus, although this IOL significantly induced HOA. The intermediate VA and the photopic contrast sensitivity were better with the Restor IOL.

Patient satisfaction with multifocal and toric multifocal IOLs is very good, ranging from 93% to 95%.

Complications

The most common visual symptoms of multifocal IOLs are glare and halos. These phenomena are secondary to the light division into two or more foci that happens with a multifocal IOL; the light in the out-of-focus image reduces the contrast of the in-focus image.

Other symptoms include starbursts, shadows, and negative and positive dysphotopsia. A decrease in contrast sensitivity has been reported also. Multifocal aspherical IOLs have been developed to improve these visual phenomena. A meta-analysis compared the visual outcomes between aspherical and spherical multifocal IOLs, and aspherical multifocal IOLs achieved better image quality than spherical multifocal IOLs and also had less spherical aberrations.

Although no multifocal IOL design exists without night vision disturbances, patients may adapt to them in a 6-month period through a process of neuroadaptation, which is faster with fully diffractive IOLs because the pupil does not affect the visual outcome.

Posterior capsule opacification is the most common complication after cataract surgery. A study compared the ND:YAG capsulotomy rates after the implantation of the FineVision Micro F and AT LISA tri 839MP trifocal IOLs, and the ND:YAG capsulotomy rate was significantly higher with the AT LISA tri 839MP IOL, although both IOLs had the same incidence of posterior cystoid macular edema.

It is important to note that not every patient is going to adapt to the multifocality and visual side effects, and some may want an IOL exchange (photopic phenomena and waxy vision can only be treated by IOL exchange). Kamiya et al. reported the reasons for multifocal IOL explantation. The principal reason, accounting for 36% of all cases, was decreased contrast sensitivity; of these, 34% was for photopic phenomenon, 32% for unknown origin, including neuroadaptation failure, 20% for incorrect IOL power, 14% for preoperative excessive expectation, 4% IOL decentration, and 4% for anisometropia. It is important to note that 70% of the eyes from which the multifocal IOL was explanted had an UDVA of 20/20 or better, which means that the side effects of multifocal IOLs can be really disturbing for the patient ( Table 3.10.5 ). See Table 3.10.6 for a review on Multifocal IOLs.

1)

IOLs With Change in Axial Position, Single Optic

2)

IOLs With Change in Axial Position, Dual Optic

Synchrony (Visiogen Inc.)

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  Type: one-piece dual optic

  
  
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  Material: silicone

  
  
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  Power range: +16.00 D to +28.00 D in 0.5 D steps

The anterior IOL component has a high plus power beyond that required to produce emmetropia, and the posterior component has a minus power to return the eye to emmetropia. A bridge with a spring function connects the two components. Once the IOL is in the capsular bag, the tension of the bag compresses the optics. This leads to strain energy in the haptics that is released when there is an attempt to accommodate ( Fig. 3.10.17 ).

Synchrony IOL.

(Image from Bohórquez V, Alarcon R. Long-term reading performance in patients with bilateral dual-optic accommodating intraocular lenses. J Cataract Refract Surg 2010;36:1880–6.)

A comparison of the visual and ocular performances between the Crystalens HD and the Synchrony IOL was made by Alió et al. No statistically significant differences occurred in UDVA, CDVA, and near or intermediate visual outcomes between the two IOLs. Reading acuity and reading speed were similar in both groups. Contrast sensitivity was significantly better in patients who received the Synchrony IOL. HOA were higher in the Crystalens HD group. Both IOLs had limitations in providing adequate near visual outcomes.

Bohórquez et al. evaluated reading ability at 1 and 2 years after the implantation of the Synchrony IOL. The reading speed, mean reading acuity, and mean critical print size were significantly better by 2 years postoperatively. They concluded that these results were a consequence of true accommodation, although the reasons for the improved reading skills at 2 years postoperatively were not fully clear.

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  Commercially available: No, it has been discontinued

3)

IOLs With Change in Shape or Curvature

Nulens (DynaCurve).

This IOL consists of polymethyl methacrylate (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. 3.10.18 ).

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  Mechanism of action: The piston is pressed, making the flexible gel bulge and resulting in an increase or decrease in IOL optical power.

  
  
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  It is inserted at the sulcus and must be implanted through a limbal incision of 9 mm.

  
  
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  It can provide up to 10.00 D of accommodation, improving near visual acuity without compromising DVA.

  
  
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  Commercially available: No

Nulens IOL in the Human Eye.

(Image from Alió JL, Ben-nun J, Rodríguez-Prats JL, et al. Visual and accommodative outcomes 1 year after implantation of an accommodating intraocular lens based on a new concept. J Cataract Refract Surg 2009;35:1671–8.)

4)

IOL With Change in Refractive Index or Power

Lumina (Akkolens).

This IOL consists of two optical elements, each having an elastic U-shaped loop with a spring function, and nonelastic connections to the main body of the lens ( Fig. 3.10.19 ).

Lumina IOL.

(Image from Alió JL, Simonov A, Plaza-Puche AB, et al. Visual outcomes and accommodative response of the Lumina accommodative intraocular lens. Am J Ophthalmol 2016;164:37–48.)

The optics are aspherical, The anterior one has a power of 5.0 D, and the power of the posterior one depends on the required correction of the eye (10–25 D).

It must be implanted at the sulcus, and its size is customized based on the sulcus to sulcus diameter, as measured by OCT at the 12 o’clock meridian.

During accommodation, the IOL is compressed by the contraction of the ciliary muscle, and the optics move in opposite directions, increasing the optical power of the lens. When the muscle relaxes, the springs force the elements back to their original state, decreasing the optical power.

It has been proven through subjective and objective methods that the Lumina IOL improves near, intermediate, and far vision without affecting contrast sensitivity and with an accommodative power between 1.5 and 6.0 D.

Comments.

The long-term effectiveness of accommodating IOL implantation for presbyopia treatment still has to be demonstrated ( Fig. 3.10.20 ).

Types of Presbyopic IOLs.

Scleral Expansion Bands

This treatment is based on Schachar’s theory of accommodation, which states that presbyopia is secondary to an increase in the lens diameter, which causes a reduction in the space between the lens and the ciliary body such that upon contraction the zonules can no longer exert their effect on the lens due to a loss of tension.

The Refocus Group is conducting a phase III study of a new scleral implant surgery. Four PMMA segments are inserted in scleral tunnels at a depth of 400 µm, 4 mm from the limbus to restore accommodation. Preliminary reports indicate good uncorrected near and intermediate vision without compromise of distance vision. Primary outcomes are still pending.

Topical Treatment

This is an emerging topic that is under clinical evaluation; the mechanism of action is through ciliary body stimulation, miosis, and lens softening.

FOV Tears

A topical treatment is available for the correction of near vision, with scientific evidence reporting a gain of two to three lines of UCVA. The ophthalmic solution contains pilocarpine, phenylephrine, polyethylene glycol, nepafenac, pheniramine, and naphazoline, and this combination stimulates the contraction of the ciliary body and maintains a physiological pupil diameter. FOV tears are commercially available in some Latin American countries.

Liquid Vision

This is a combination of aceclidine (parasympathomimetic) and tropicamide. Its mechanism of action is through a pinhole effect. The pilot study reported a gain of more than three lines of near vision. It is being tested in a phase IIb trial.

EV06 (Encore Vision)

An increment of the lens elasticity may be achieved by topical treatment with lipoic acid choline ester 1.5% (EV06, Encore Vision), which reduces the lens protein disulfides.

The lens disulfide bonds that form between the crystalline proteins are broken down because of the dihydrolipoic acid (a reduced active agent of lipoic acid), thus increasing the lens elasticity. A phase I/II study has shown good outcomes.