Pinhole camera effect in small-aperture implant corrects presbyopia in patients

May 19, 2020

When paired with multifocal extended-depth-of-field technology, the IC-8 lens delivers extended depth of focus near, far, and intermediate ranges while reducing halo and glare. 

Special to Ophthalmology Times

The IC-8 small-aperture IOL (AcuFocus), which is CE marked and currently under investigation by the FDA, employs the pinhole camera effect to correct presbyopia. 

By flattening the defocus curve on both the myopic and hyperopic sides, the IOL essentially creates a small amount of myopia, thereby extending the patient’s depth of focus and eliminating visual effects from corneal astigmatism or other irregularities. 

This is a 1-piece hydrophobic acrylic ocular implant that comprises an embedded opaque annular mask with a central aperture. Aligned light rays converge through the 1.36-mm central aperture, while peripheral defocused and, often, aberrated rays are blocked from disrupting the image.

Related: Presbyopia-correcting IOLs enhance customization

As a result, patients experience a continuous range of vison from near to far, including the increasingly important intermediate range. 

For most of us, the intermediate range (1.5 feet to 7 feet away) is a critical zone of activity. We eat the majority of our meals, work at our desks, and watch our large-screen media in this space. This distance represents the area where many people earn their living, including refractive surgeons. 

Originally intended to be combined with a monofocal IOL, it has been found that when paired with a multifocal IOL, the IC-8 is better than previous alternatives at enhancing visual acuity at intermediate distances.

As a result, this lens has the potential to benefit this underserved cohort. Likewise, patients who have undergone previous refractive procedures are becoming more common. 

As they proliferate, so does our necessity for techniques and technologies tailored to support their special needs. The IC-8 has shown good outcomes in these “veteran” surgical patients. 

Surgeons are only now beginning to appreciate the additional benefits made possible by combining the small-aperture lens with IOLs that function on completely different optical principles. Experimentation is ongoing, and this novel strategy may ultimately lead us to maximize the full potential of the IOL, providing patients with truly satisfying customized outcomes.

Related: Changing focus of accommodating IOLs now reaching a new level 

Lens attributes
Low-add multifocal lenses have been shown to improve intermediate visual acuity and offer surgeons the ability to further individualize patients’ visual outcomes, especially when mixed with another refractive technology. Combining a multifocal lens with a different type of lens can also act to minimize glare and halo, an intrinsic characteristic of low-add multifocal lens optics. 

It is well known that most types of presbyopia-correcting IOLs-including multifocal refractive and diffractive, and even the newest trifocal technology-sacrifice distance vision to some extent in order to correct near vision and induce a variable amount of dysphotopsias.1

One study of the AcrySof ReSTOR +2.50 D IOL (Alcon) found it provided good intermediate and functional near vision for patients who did not want the higher potential for visual disturbances associated with the +3.00 D version of the same IOL but wanted more near vision than a monofocal IOL provides.2

Another prospective comparative investigation evaluated bilateral cataract surgery using the +3.00 D AcrySof IOL or a +4.00 D power of the implant.3

The +3.00 D IOL provided superior uncorrected distance visual acuity, significantly better uncorrected intermediate visual acuity at 40, 50, 60 and 70 cm, and functional reading acuity at 38.9 cm. Eyes with the +3.00 D IOL had better intermediate vision than those with the +4.00 D model without compromising distance and near visual acuity.

Related: Accurate data key for planning toric IOL surgery

Multi-focal extended depth-of-focus
The Lentis Mplus LS-313 MF20 (Teleon; available in Europe but not in the United States) is a foldable, 1-piece, aspherical multifocal posterior chamber IOL that extends a patient’s depth of focus. Its refractive rotationally asymmetric design helps minimize the loss of light to below approximately 7%, thereby improving contrast and retinal image quality. 

An evaluation of the implant with +2.00 D of near add compared with +3.00 D found superior visual outcomes from far distance to a near of about 25 cm with the latter lens. The +2.00 D demonstrated excellent visual results from a far distance to an intermediate distance of about 50 cm.4

Related: Advanced toric IOL calculator improves refractive outcomes

Anchor with small-aperture approach
Unlike the aforementioned multifocal implants, the IC-8 IOL functions because of the pinhole effect. It reduces scattered light and permits only parallel rays to reach the macula. Depth of focus is extended and visual disturbances such as glare and halo are reduced.

Small-aperture technology can even overcome problems with corneal asphericity and irregularities. Astigmatism up to 1.50 D can be corrected with the lens alone.5

The IC-8 IOL is typically implanted in the nondominant eye, with a monofocal lens in the contralateral eye. To enhance acuity, the small-aperture IOL can be paired with other technologies such a multifocal, a low-add multifocal, or even a trifocal lens.

The basic idea is that using different types of implants can enhance the sharpness of vision at near, intermediate, and distance and minimize the side effects of the competing technologies.

Related: Presbyopia-correcting IOLs: Expanding, improving last frontier 

Small-aperture plus extended depth-of-focus technology
 
The ongoing prospective, multicenter MOSAIC clinical trial was undertaken to evaluate visual outcomes from the combination of the IC-8 IOL and the Lentis MF20.6

Our group presented 5-month follow-up data on 13 patients with bilateral implantation of the IC-8 IOL with the Lentis LS-313 MF20 with +2.00 D of near add. We examined the following parameters:

> uncorrected and corrected (binocular) far, intermediate, and near visual acuity;

> defocus curves;

> Salzburg Reading desk test results; and

> photic phenomena (halo and glare simulator).

The MOSAIC trial included 26 eyes of 13 patients with cataracts (average age, 68.5 ± 10.8 years). The targeted refraction for the eyes implanted with the IC-8 IOL was -0.43 ±0.18 D with an achieved refraction of 0.42 ± 0.41 D. 

The achieved refraction was within ±0.50 D 62% of the time. The targeted refraction for the eyes implanted with the MF20 was -0.15 ± 0.16 D, and the achieved refraction was -0.33 ± 0.42 D. Eighty-five percent of the time, the achieved refraction was within ± 0.50 D.

Related: Light-adjustable IOL technology creates novel treatment window

We found that patients implanted with the LS-313 MF20 had excellent binocular visual acuity at far and intermediate distances, as well as functional vision at near. They had functional reading acuity at near and intermediate distances, and there was a low incidence of photic phenomena.

The combination of the small-aperture implant with a low-add multifocal lens such as the Lentis LS-313 MF20 is a good treatment option for patients who are motivated to achieve spectacle independence. 

Implications and conclusions
Multifocal lens designs can exhibit pronounced peaks and troughs, but the IC-8 IOL provides uninterrupted functional vision over 3.00 D of defocus.7

The small-aperture principle has the ability to produce a high-quality, full range of vision without blurry zones and is more forgiving of refractive error misses or surprises. 

The IC-8 IOL implant has been shown to provide good visual outcomes in post-LASIK and post-RK eyes.8 Patients with corneal irregularities can benefit from the technology’s ability to reduce aberrations. 

When paired with multifocal extended depth-of-focus technology, the IC-8 delivers excellent extended depth of focus at near, far, and intermediate ranges while reducing halo and glare. It can enhance physicians’ ability to customize successful visual outcomes for each patient.

Based on the simple, proven, and ancient understanding of the pinhole’s effect on light ray alignment, this IOL is a versatile tool to help patients who have undergone cataract surgery achieve their paramount postoperative visual goals. 

Read more cornea content here 

Gerd U. Auffarth, MD, PhD, FEBO
E: auffarthg@aol.com
Dr. Auffarth is a chairman and medical director of the Department of Ophthalmology of the University Clinic of Heidelberg, Germany; director of the David J. Apple, MD, International Laboratory of Ocular Pathology; and director of the International Vision Correction Research Center in Heidelberg. He receives research grants and lecture fees from AcuFocus, Alcon, Biotech, Hoya, Johnson & Johnson, KOWA, Oculentis, Rayner, and Zeiss.

References:

Gundersen KG, Potvin R. Comparative visual performance with monofocal and multifocal intraocular lenses. Clin Ophthalmol. 2013;7:1979-1985.

de Vries NE, Webers CA, Montés-Micó R, Ferrer-Blasco T, Nuijts RM. Visual outcomes after cataract surgery with implantation of a +3.00 D or +4.00 D aspheric diffractive multifocal intraocular lens: comparative study. J Cataract Refract Surg. 2010;36(8):1316-1322.

Linz K, Attia MS, Khoramnia R, et al. Clinical evaluation of reading performance using the Salzburg Reading Desk with a refractive rotational asymmetric multifocal intraocular lens. J Refract Surg. 2016;32(8):526-532. 

Venter JA, Pelouskova M, Bull CE, et al. Visual outcomes and patient satisfaction with a rotational asymmetric refractive intraocular lens for emmetropic presbyopia. J Cataract Refract Surg. 2015;41(3):585-593. 

Calvo-Sanz JA, Sánchez-Tena MA. Characterization of optical performance with defocusing curve: analysis of two refractive intraocular lens models with high and medium addition. J Optom. 2018 Oct 31. 

https://www.healio.com/ophthalmology/cataract-surgery/news/online/%7B2809ee76-e466-43fe-b70b-dd94ff661925%7D/video-edof-iol-using-pinhole-effect-lessens-ocular-effects.

Dick HB, Elling M, Schultz T. Binocular and monocular implantation of small-aperture intraocular lenses in cataract surgery. J Refract Surg. 2018;34(9):629-631. 

Dick HB. Small-aperture strategies for the correction of presbyopia. Curr Opin Ophthalmol. 2019;30(4):236-242.