HOW IS EXTENDED DEPTH OF FOCUS ACHIEVED WITH A SMALL-APERTURE LENS? The pinhole effect of the Kamra inlay may have similar efficacy when transferred to an IOL.

BY PABLO ARTAL, PhD COVER FOCUS COVER

Life happens on small and grand scales, through the central aperture. The IOL mask is 15% smaller right in front of us and from afar; most of in diameter than the one used in the Kamra inlay to us want to experience all of it. Since the first account for its more posterior placement. It also has fewer bifocal IOLs were developed in the 1980s, microperforations. scientists and manufacturers have been on Investigators collected data from more than 20,000 a dedicated mission to provide individuals patients worldwide with the Kamra inlay. They found with great vision at all distances after cata- that patients with the inlay gained a mean 3 lines of near ract surgery. visual acuity and 1 line of intermediate visual acuity, with a Following those early bifocal lenses, the development decrease of only 0.5 lines of monocular distance acuity and of multifocal lenses provided good vision at multiple dis- no decrease of binocular distance acuity.5 Results with the tances, and accommodative IOLs attempted to mimic the Kamra inlay remained stable over 60 months, even as pres- focusing ability of the natural eye. However, although many byopia progressed. of these options have been successful in achieving good In an eye with plano refraction, the small-aperture tech- visual acuity at distinct distances, this has often come at nique can provide an increased range of vision of about the price of decreased overall quality of vision.1-3 2.5 D. If that is combined with slight myopia (-0.75 D), Rather than creating two or three focal points, extended a patient can achieve a continuous functional range of depth of focus (EDOF) technologies aim to increase overall vision of up to 3.5 D (Figure 1). When the Kamra inlay depth of field, creating a fluid visual experience that pro- was compared against three -correcting IOLs, it vides better near vision than monofocal technologies and, performed well at all distances, providing continuous func- at the same time, less trouble with glare and halos than tional vision across a large dioptric range (Figure 2).5 multifocal IOLs. There are a number of EDOF lenses on Contrast sensitivity is an important aspect of quality of the market, and they achieve their desired visual range via vision and EDOF. In a comparison of patients implanted a variety of methods. The Symfony IOL (Abbott Medical with the Kamra inlay or with one of three presbyopia- Optics) has a unique echelette design. (The manufacturer correcting IOLs, patients with the inlay had better contrast refers to this lens as providing an extended range of vision, sensitivity than patients with multifocal IOLs. Patients also as opposed to EDOF.) The Light Adjustable Lens (Calhoun had significantly better binocular contrast sensitivity when Vision) can be shaped to provide additional spherical aber- ration through postoperative irradiation of the silicone mate- rial with ultraviolet light.4

SMALL-APERTURE APPROACH AT A GLANCE Another approach to EDOF is used in the IC-8 IOL • Extended depth of focus technologies aim to (AcuFocus), a lens adaptation of the Kamra corneal inlay increase overall depth of field. (AcuFocus) for presbyopia. This one-piece hydrophobic acrylic IOL has a centrally located opaque annular mask • A small aperture or pinhole effect is one method of measuring 3.23 mm in total diameter with a 1.36-mm achieving extended depth of focus. central aperture. The IC-8 IOL provides EDOF using the • An IOL using this approach has provided improved pinhole effect, blocking unfocused peripheral light rays near, intermediate, and distance UCVA in patients. and isolating more focused central and paracentral rays

68 CATARACT & TODAY | JANUARY 2016 COVER FOCUS Courtesy of AcuFocus

Figure 1. Comparison of patient defocus curves in an untreat- ed presbyopic eye and an eye 1 year after Kamra implantation.

Figure 2. Monocular defocus curves show visual acuity Courtesy of AcuFocus (logMAR) versus defocus lens power at 6 months after Kamra AVAILABLE EDOF inlay or presbyopia-correcting IOL implantation. compared with both those with either multifocal IOLs or TECHNOLOGIES accommodating IOLs.5

INVESTIGATING SMALL-APERTURE EFFECTS Using a binocular adaptive optics instrument, we simu- lated the effect of the small-aperture inlay and demon- strated a significant increment in depth of focus.6 There was a benefit in stereoacuity. We also compared stereo vision with two methods of presbyopia correction—mon- oviosion and the small-aperture effect—and found that although monovision correction reduced stereoacuity, the • IC-8 IOL (AcuFocus) small aperture preserved it at nearly normal values.7 • Hoya Because small-aperture devices function by eliminating some peripheral rays of light, we thought it important to • Light Adjustable Lens evaluate how placement of the small-aperture mask affects (Calhoun Vision) visual performance. Using an eye model, we determined that, in eyes with little astigmatism and low aberrations, • MiniWell (Sifi Medtech) the optimum centration of the small aperture was near the corneal reflex position.8 • RevIOL Tri-ED (VSY) Another important issue related to the small aperture • Symfony IOL (Abbott is possible reduction of luminance. In that context, we recently analyzed the visual effect of the Stiles-Crawford Medical Optics) (SC) peak decentration in patients with small apertures.9 The SC effect produces a change in the apparent bright- ness of rays entering the eye through different pupil posi- tions. The SC peak is typically located 0.33 mm nasal to the pupil center, but it can be significantly more decentered in some patients. The small aperture is typically centered on the pupil or on the first Purkinje image. My colleagues and I evaluated the impact of the SC peak location on the visual performance of eyes with a small aperture. We found that the quality of the retinal image in

JANUARY 2016 | CATARACT & REFRACTIVE SURGERY TODAY EUROPE 69 eyes with a small aperture was not affected by the location of the SC peak in most patients. Only in cases in which the SC peak was decentered by more than 2 mm was there a reduction in mesopic visual acuity. This suggests that centration of a small-aperture inlay or IOL is not a critical issue.

CONCLUSIONS The IC-8 lens received the CE Mark, but the manufacturer is conducting a postapproval study in 12 centers in Europe to refine the procedure. The lens is implanted monocularly, and an IOL of the surgeon’s choice

COVER FOCUS COVER is used in the other eye. A recent report found that 12 cataract patients who were implanted monocularly with the IC-8 lens showed significant improvement in distance, intermediate, and near visual acuity.10 At 12 months, mean monocular near, intermediate, and distance UCVA improved significantly in these patients, from J6 to J2 (P = .0051), from 20/44 to 20/21 (P = .0051), and from 20/32 to 20/20 (P = .001), respectively. All eyes maintained 20/40 or better visual acuity over a range of +0.50 D to -1.50 D of defocus, while patients perceived only a small magnitude of visual symp- toms that they rated on the low end of a severity scale.10 The EDOF lens category sits in the treatment toolbox between monofocal and multifocal IOLs. These lenses can be used in patients without retinal disease who would not be happy with standard diffractive multifocal IOLs but who desire some spectacle independence. These lenses are fill- ing a previously unmet need and providing many patients with an option for good quality of vision at a range of dis- tances. n

1. Davison JA, Simpson MJ. History and development of the apodized diffractive intraocular lens. J Cataract Refract Surg. 2006;32(5):849-858. 2. Bellucci R. Multifocal intraocular lenses. Curr Opin Ophthalmol. 2005;16(1):33-37. 3. Pepose JS, Wang D, Altmann GE. Comparison of through-focus image sharpness across five presbyopia-correcting intraocular lenses. Am J Ophthalmol. 2012;154(1):20-28. 4. Villegas EA, Alcón E, Mirabet S, Yago I, Marín JM, Artal P. Extended depth of focus with induced spherical aberration in light- adjustable intraocular lenses. Am J Ophthalmol. 2014;157(1):142-149. 5. Vilupuru S, Lin L, Pepose JS. Comparison of contrast sensitivity and through focus in small-aperture inlay, accommodating intraocular lens, or multifocal intraocular lens subjects. Am J Ophthalmol. 2015;160(1):150-162. 6. Tabernero J, Schwarz C, Fernández EJ, Artal P. Binocular visual simulation of a corneal inlay to increase depth of focus. Invest Ophthalmol Vis Sci. 2011;52:5273-5277. 7. Fernández EJ, Schwarz C, Prieto PM, Manzanera S, Artal P. Impact on stereo-acuity of two presbyopia correction approaches: monovision and small aperture inlay. Biomed Opt Express. 2013;4:822-830. 8. Tabernero J, Artal P. Optical modeling of a corneal inlay in real eyes to increase depth of focus: optimum centration and residual defocus. J Cataract Refract Surg. 2012;38:270-277. 9. Artal P, Prieto P, Robles C, Manzanera S, Holladay J. Visual effect of the Stiles-Crawford peak location in patients with a small- aperture corneal inlay. Paper presented at: European Society of Cataract and Refractive Surgeons Annual Meeting; September 5-9, 2015; Barcelona, . 10. Grabner G, Ang R, Vilupuru S. The small aperture IC-8 intraocular lens, a new concept for added depth of focus in cataract patients. Am J Ophthalmol. 2015;160(6):1176-1184.e1.

Pablo Artal, PhD n Professor, Laboratorio de Óptica, Universidad de Murcia, Spain n [email protected] n Financial disclosure: Consultant (AcuFocus)

70 CATARACT & REFRACTIVE SURGERY TODAY EUROPE | JANUARY 2016