Article

Small Aperture Technology Poised to Shake Up IOL Landscape

First-of-its-kind small aperture lens offers a solution for a true extended range of vision with the reliability of a monofocal lens.

THE IC-8 IOL (ACUFOCUS, INC.) LEVERAGES THE SIMPLE, WELL-understood principle of small aperture optics to provide cataract patients with a true extended depth of focus. Once approved, the lens will be the first and only technology available in the United States that combines the small aperture effect with an aspheric monofocal lens implant, to deliver a reliable, continuous range of vision.

Emerging Applications

Small aperture optics are a dynamic, physiologic solution to presbyopia correction. This novel mechanism of action—first launched by AcuFocus in the form of a corneal inlay—is constantly evolving. Our industry has recently seen the approval of the first pharmaceutical based on this principle to enhance vision in early presbyopia, and several more of these agents are in the pipeline.

When used appropriately, the small aperture approach has the ability to both mitigate the effects of presbyopia and lessen the impact of corneal aberrations in cataract patients, improving vision in eyes with corneal irregularities, scars, or iris damage. Reporting findings in Current Opinions in Ophthalmology, H. Burkhard Dick, MD, wrote that perceived brightness through a small aperture is greater than what would be expected from theoretical calculations.1 He wrote, “This is likely due to a combination of binocular effects, the Stiles-Crawford effect, and neuroadaptation.”

How It Works

The wavefront-filtering, small aperture design of the IC-8 IOL channels central light rays to the retina and filters out stray and unfocused peripheral light that degrades image quality. This is how the mechanism minimizes the impact of corneal aberrations, providing an increased range of vision from far to near with more than 2.5D of extended depth of focus.2-5

The aspheric hydrophobic implant is more forgiving of sphero-cylindrical residual refractive errors compared with multifocal implants, tolerating up to 1.00D deviation from the target manifest refraction spherical equivalent.6 In contrast, anything over 0.75D of residual sphere with multifocal technology compromises visual acuity and spectacle independence.6

The acrylic UV-blocking advanced monofocal lens features an embedded FilterRing component (opaque ring) comprised of polyvinylidene fluoride and carbon black. The FilterRing component measures 3.23 mm in total diameter and contains a 1.36 mm central aperture. The overall lens length is 12.5 mm and the optic is 6.00 mm. Despite not being a toric lens, the IC-8 IOL provides consistent outcomes for patients with no, or as much as 1.5D, corneal astigmatism, even in the event of a refractive surprise.

The IC-8 intraocular lens, from AcuFocus, Inc.

Clinical Study And Our Experience

We took part in the prospective, multicenter, 1-year Investigational Device Exemption clinical study to evaluate the safety and effectiveness of the IC-8 IOL. The study sought to determine if the IC-8 IOL, when implanted in conjunction with a monofocal or monofocal toric IOL in the fellow eye, would demonstrate better binocular intermediate and near visual acuity and similar distance visual acuity compared to bilateral aspheric monofocal or monofocal toric IOLs. There were 343 study subjects and 110 control subjects enrolled and followed for 12 months. Those in the study arm were implanted with an IC-8 IOL in one eye and a control (monofocal or monofocal toric) IOL in their fellow eye. Control group subjects were bilaterally implanted with monofocal or monofocal toric IOLs.

We are excited by the results we have seen from our patients and look forward to adding the lens to our lineup of presbyopia-correcting options—certainly the more choices there are for patients, the better. Although not included in this study, based on our understanding of the IC-8’s mechanism of action, this option could be especially important for those individuals who may not be candidates for other types of multifocal lenses due to corneal irregularities. We also appreciate that it can mitigate up to 1.5D astigmatism without the need for toricity.7 Due to the small aperture expanding the depth of focus, this lens offers a larger landing zone, enabling it to be more forgiving even in challenging situations.

At our center, the IC-8 IOL surgeries during the clinical trial were uncomplicated; the lens is straightforward to implant and behaves similarly to other aspheric monofocal IOLs with which we are familiar. Patients we saw were happy with their postoperative result, achieving a greater range of vision with minimal effects from the small aperture in terms of dysphotopsia. Neuroadaptation was not an issue.

A significant swath of patients are good candidates for the IC-8 IOL, as long as they are free from any central corneal opacity or central macular pathology. We believe patients with previous LASIK, for example, and those with irregular astigmatism in whom multifocality may not be a viable option, can benefit from small aperture technology. Many of the patients presenting for cataract surgery have had refractive surgery and—other than monofocal technology—our options have been limited.

Growing Population Of Complex Cornea Patients

We frequently see patients at the time of cataract surgery who also present with a complex cornea that can affect quality of vision after cataract surgery. Cataract patients can present with a complex cornea due to a variety of causes, from previous refractive surgery to scarring to mild basement membrane dystrophy. Estimates are that approximately 12% to 14% of patients presenting for cataract surgery do so with a complex cornea.8 That number may actually be higher; however, a panel convened to create a consensus on corneal irregularity reported that approximately 24% of the members’ preoperative cataract patients have irregular or complex corneas.9 Further, a review of 200 patients (400 eyes) found that approximately 25% of patients scheduled for cataract surgery had abnormal corneal topography without a history of previous corneal surgery.10

IOL calculations are more challenging in these complex cornea eyes. Therefore, the added depth of focus provided by the IC-8’s small aperture may make it a bit easier to hit the refractive target. Multifocality, on the other hand, comes with a risk of distortion in such cases, and, in those with irregular astigmatism, hitting the refractive target is more challenging. Plus, there may be limited laser enhancement potential to maximize that vision in this population. For those with smaller amounts of astigmatism, lower-powered toric implants do not offer a range of vision. A small aperture IOL allows us to neutralize the astigmatism while also getting more depth of focus.

A recent prospective interventional case series by Shajari et al. looked at 17 eyes of 17 patients with severe corneal irregularities due to keratoconus, previous penetrating keratoplasty, post radial keratotomy, or ocular trauma implanted with the IC-8 IOL.11 The investigators evaluated the reduction in higher-order aberrations and improvement in central visual acuity in these eyes with an average higher order aberration of RMS 0.75 µm at 3 months postoperatively. They found that, in all 17 patients, the corrected distance visual acuity improved from 0.37 ±0.09 to 0.19 ± 0.06 logMAR 3 months postoperatively (P < .0001). Similarly, postoperative uncorrected distance visual acuity, uncorrected intermediate visual acuity, and uncorrected near visual acuity improved significantly in 100%, 88%, and 88% of patients, respectively. Further, the group found that the defocus curve showed best results at 0.17 logMAR with a defocus of -0.5D. Importantly, patient satisfaction was high, with more than twice as many reporting a greater ability to perform daily tasks such as reading street signs and newspapers, and descending stairs.

Conclusion

Expected to be FDA approved and available later this year, the IC-8 IOL represents a completely different approach to presbyopia correction than other IOLs in the United States. The implant fills a gap in the available technology, providing a great option for many of our cataract patients, including patients who have had previous refractive surgery or an irregular cornea due to some other cause. Sometimes in medicine a simple principle can also be elegant, compelling, and groundbreaking. ■

References

  1. Dick HB. Small-aperture strategies for the correction of presbyopia. Curr Opin Ophthalmol. 2019;30(4):236-242. doi: 10.1097/ICU.0000000000000576.
  2. Grabner G, Ang RE, 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. doi:10.1016/j. ajo.2015.08.017.
  3. Dick HB, Piovella M, Vukich J, et al. Prospective multicenter trial of a small-aperture intraocular lens in cataract surgery. J Cataract Refract Surg. 2017;43(7):956-968. doi:10.1016/j.jcrs.2017.04.038.
  4. Tucker J, Charman WN. The depth-of-focus of the human eye for Snellen letters. Am J Optom Physiol Opt. 1975;52(1):3-21. doi:10.1097/00006324-197501000-00002.
  5. Ang RE. Visual performance of a small-aperture intraocular lens: first comparison of results after contralateral and bilateral implantation. J Refract Surg. 2020;36(1):12-19. doi: 10.3928/1081597X-20191114-01.
  6. Braga-Mele R, Chang D, Dewey S, et al. Multifocal intraocular lenses: relative indications and contraindications for implantation. J Cataract Refract Surg. 2014;40(2):313–322. doi: 10.1016/j.jcrs.2013.12.011.
  7. Ang RE. Small-aperture intraocular lens tolerance to induced astigmatism. Clin Ophthalmol 2018;12:1659-1664. doi: 10.2147/OPTH.S172557.
  8. Data on file Acufocus.
  9. 2020 Global Consensus on Corneal Irregularity: Expert Panel Offers Recommendations for Defining, Diagnosing, and Treating Irregular Corneas. Supplement to Cataract & Refractive Surgery Today / Europe. November/December 2020. https://crstoday.com/wp-content/uploads/sites/4/2021/01/0121CRST-CRSTES_Evolve-2032-Corneal-Irregularity-Consensus-Paper.pdf . Accessed January 13, 2022.
  10. Frank B, Trattler W, Mccabe S, et al. The incidence of topographic abnormalities in patients scheduled for cataract surgery (abstract). Invest Ophthalmol Vis Sci. 2014; 55:2477. https://iovs.arvojournals.org/article.aspx?articleid=2267825 .
  11. Shajari M, Mackert MJ, Langer J, et al. Safety and efficacy of a small aperture capsular bag fixated intraocular lens in eyes with corneal irregularities. J Cataract Refract Surg. 2020;46:188-192.