Small-Aperture Strategies for the Correction of Presbyopia

H. Burkhard Dick

Disclosures

Curr Opin Ophthalmol. 2019;30(4):236-242. 

In This Article

Part I: Small-aperture Platforms

Posterior Chamber Intraocular Lens

The IC-8 small-aperture IOL (AcuFocus, Irvine, California, USA) is a single-piece hydrophobic acrylic IOL intended for implantation in the capsular bag, with modified C haptics, and an overall diameter of 12.5 mm. The biconvex aspheric optic is 6.0 mm in diameter with a 360-degree square posterior edge. The embedded annular mask has an outer diameter of 3.23 mm and a central aperture measuring 1.36 mm in diameter (Figure 1).

Figure 1.

IC-8 intraocular lens 1 week after femtosecond laser-assisted cataract surgery using the Catalys Precision Laser System (Johnson & Johnson, Santa Ana, California, USA).

The IC-8 IOL is CE marked and is commercially available in select markets in Europe, Australia and New Zealand. The lens is currently in clinical trials in the United States. Results from a multicenter postmarket European trial were recently published.[1] Patients (n = 105) with bilateral cataract were implanted with the IC-8 IOL in one eye, with a refractive target of –0.75 D, and an aspheric, colorless, monofocal IOL in the fellow eye with a plano target. Six months after implantation, monocular uncorrected distance visual acuity (UDVA) was 0.87 logMAR (20/23), uncorrected intermediate acuity (UIVA) was 0.83 logMAR (20/24), and uncorrected near acuity (UNVA) was 0.66 logMAR (20/30).

Binocularly, 99, 95, and 79% of patients achieved 20/32 or better UDVA, UIVA, and UNVA, respectively. The vast majority of patients (95.9%) reported they would have the procedure again, while four patients (4.1%) said they would not. Most (84.8%) reported using spectacles occasionally to never, 9 patients (8.6%) reported using them 50% of the time, and 7 patients (6.7%) reported using them often to most of the time.[1]

The eyes with the monofocal IOLs had significantly better monocular contrast sensitivity than the eyes with the small-aperture IOLs at 1.5, 3.0, 6.0, and 12.0 cpd (P < 0.003). Eyes with the monofocal IOL had significantly better monocular mesopic contrast sensitivity with glare than eyes with the small-aperture IOL eyes at 1.5, 3.0, and 6.0 cpd (P < 0.0001). However, binocular contrast sensitivity matched the monocular contrast sensitivity achieved in the monofocal IOL eye.[1]

Patients in this study and others have demonstrated very good tolerance to residual refractive error, making a small-aperture IOL more forgiving and diminishing the need for intraoperative orientation or aberrometry systems. In the European multicenter trial, mean UIVA and UNVA remained at 20/25 and 20/32, respectively, for up to 1.5 D of residual astigmatism in eyes with the small-aperture IOL. In fact, there were no clinical or statistical differences between eyes with at least 0.75 D of cylinder and those with 0.76--1.50 D.[1]

Ang also reported that astigmatic patients in a single-site prospective clinical trial who were implanted with an IC-8 IOL without any additional astigmatic management were able to tolerate up to 1.50 D (and in some cases, even 2.00 or 2.50 D) of refractive astigmatism.[2] Mean UDVA in this study was 0.08 ± 0.08 logMAR (20/24) at 1.50 D of cylinder defocus, 0.18 logMAR ± 0.08 (20/30) at 2.00 D of defocus, and 0.24 logMAR ± 0.07 (20/35) at 2.50 D of defocus. Eight of 10 patients achieved 20/25 or better vision with 1.50 D of cylinder defocus, and all patients were 20/30 or better. The author notes that this small-aperture IOL may be able to bridge the gap between monofocal and monofocal toric IOLs for correction of low levels of astigmatism.[2]

The IC-8 IOL has also provided good visual outcomes in post-LASIK[3] and post-RK[4] eyes. These patients are typically highly motivated to maintain spectacle independence after cataract surgery, but many physicians consider them unsuitable candidates for implantation of other presbyopia-correcting IOLs. The greater degree of forgiveness of a small-aperture IOL could be beneficial in postrefractive eyes in which a greater deviation from target refraction can be expected, due to the unpredictability of IOL power calculations in such eyes.

Small-aperture IOLs also offer an opportunity to improve vision in eyes with scars, iris damage, or corneal irregularities that could be masked by the opaque annulus. Most diagnostic examinations can be performed after IC-8 lens implantation (Figure 2a and b).

Figure 2.

(a) Macular SD OCT (Spectralis, Heidelberg Engineering, Heidelberg, Germany) after implantation of an IC-8 IOL. (b) Widefield retinal imaging showing 200° fundus photography using Daytona (Optos Inc. Marlborough, Massachusetts, USA) in an eye after implantation of an IC-8 IOL.

Add on, Sulcus-implanted IOL

The XtraFocus device (Morcher, Stuttgart, Germany) is a foldable hydrophobic acrylic aperture, designed to be implanted in the ciliary sulcus of pseudophakic patients in an add on configuration. It has a black, opaque 6.0 mm diaphragm with a 1.3-mm central opening and 14.0 mm overall diameter (Figure 3). The occlusive part of the device has a concave–convex design to prevent contact with the primary IOL, which can be any monofocal IOL, including a toric lens (Figure 4). The black acrylic material of the XtraFocus device has the unique feature of being transparent to infrared light. The XtraFocus pinhole implant has been CE marked in Europe since 2016.

Figure 3.

Overview of the XtraFocus pinhole device (Morcher, Stuttgart, Germany) before intraocular implantation into the ciliary sulcus (view through the OR microscope).

Figure 4.

XtraFocus pinhole device implanted in front of a monofocal IOL (slit lamp photograph).

Several recent case reports have found the device to be effective in improving near visual acuity and managing irregular astigmatism in complex eyes.[5,6,7] However, routine use for the correction of presbyopia in normal eyes has not been studied.

Small-aperture add on designs similar to that of the Morcher lens have been tested in cadaver eyes to evaluate centration, tilt, and safety of supplementary sulcus-fixated lenses.[8]

Corneal Inlay

The IC-8 IOL design was based on that of the Kamra intracorneal inlay (CorneaGen, Seattle, Washington, USA) that preceded the IOL and is commercially available in the U.S., Europe, and around the world. The small-aperture corneal inlay is suitable for presbyopes with healthy crystalline lenses. They are removable and less invasive than intraocular options.

The Kamra inlay is a thin (6.0 μm), microperforated, opaque inlay with a 1.6-mm central aperture and a total diameter of 3.8 mm that is implanted in a femtosecond laser-created deep stromal pocket (Figure 5). Safety and efficacy, including both objective and patient-reported outcomes, have been well documented in the published literature.

Figure 5.

Well centered KAMRA corneal inlay implanted in a 5.0 mm corneal pocket created by the iFS femtosecond laser (Johnson & Johnson).

Three-year data from the U.S. clinical trials has recently been published.[9] In this study, mean monocular UNVA at three years was J2, mean UIVA was 20/25, and mean UDVA was 20/20. Binocular UDVA was 20/16. The mean range of depth of focus at 0.2 logMAR (20/32) or better improved from approximately 1.7 D preoperatively to approximately 3.0 D at 12 months and to more than 3.5 D at 0.3 logMAR (20/40).[9] Late hyperopic refractive shifts and topographic changes have been reported with the inlay. However, these seem to be linked to shallower implantation.[10,11] In a large, 4-year study in nearly 3000 patients, less than 1% of inlays were removed due to haze or refractive shift.[12]

In addition to deep implantation, achieving optimal results also requires attention to ocular surface health and a slightly myopic target in the inlay eye. This is most often achieved through a dual procedure, in which the patient undergoes both inlay surgery and laser vision correction, either simultaneously, as described recently by Moshirfar et al.,[13] or as planned sequential procedures. It has been reported that binocular mean UNVA improved from 20/32 to 20/20 at 12 months and remained stable through 48 months in a large study of patients treated with the sequential approach.[12]

Small-aperture inlays may also be combined with a monofocal IOL in pseudophakic patients to increase intermediate and near visual acuity and improve spectacle independence (Figure 6a and b). Patients implanted with an inlay in the nondominant eye in combination with monofocal IOLs achieved UNVA that was, on average, two lines better than bilateral cataract patients without inlays.[14]

Figure 6.

(a) KAMRA corneal inlay after implantation into the left eye. (b) Both eyes of the same patient (overview photo demonstrating the cosmetic effect): right eye without KAMRA inlay, left eye with intracorneal KAMRA inlay.

Contact Lenses

Small-aperture contact lenses were proposed as early as the 1950s and some models, such as the EyeLike Noan Pinhole contact lenses (Koryo EyeTech, Seoul, Korea) have been tested and sold internationally. Earlier studies reported relatively poor resolution at near and a greater loss of distance vision compared to other small aperture modalities. Given that a contact lens is designed to move freely on the tear film, it is not an ideal platform for small aperture optics, as movement of the contact lens on the eye may not keep the aperture centered.

Pupil-constricting Drops

Finally, several companies are currently exploring various agents for pharmacological pupil constriction. Frequent use of miotic agents has been associated in the past with unwanted side effects, such as headache, nausea, and ciliary spasm, and serious adverse events, including chronic inflammation, pigment dispersion, posterior synechiae, and induction of retinal detachment.[15]

Newer formulations aimed at presbyopia treatment use a combination of agents to achieve a small pupil while reducing the side effects. Among these are LiquidVision PRX-100 (Presbyopia Therapies, Coronado, California, USA), a combination of aceclidine and tropicamide; PresbiDrops/CSF-1 (Orasis Pharmaceuticals, Herzliya, Israel), with unknown components; and FOV Tears, a combination of pilocarpine 0.247%, phenylephrine 0.78%, polyetheleneglycol 0.09%, nepafenac 0.023%, pheniramine 0.034% and naphazoline 0.003%.

There are few published articles on pharmacological pupil constriction for presbyopia. Most of what is known is from anecdotal reports or early pilot studies several years ago that do not appear to have been repeated or extended. Two recent reviews of topical approaches provide more detail about these reports and about the pharmacology involved.[15,16]

The noninvasiveness of a topical approach would be a significant advantage. However, a topical drop requires daily use and would be entirely reliant on patient motivation and compliance with the drop regimen. To be successful, a pupil-constricting drop must be comfortable and well tolerated, as well as free from serious adverse events when used chronically. Rapid onset of action and/or long duration of effect would also be desirable characteristics.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....