Proven Science, New Application The IC-8 IOL

The IC-8 IOL relies on a simple and age-old ocular principle – pinhole or small aperture – to collimate central light and extend depth of focus. The implant consists of an annular opaque mask made of polyvinylidene fluoride and nanoparticles of carbon embedded into an aspheric monofocal hydrophobic acrylic lens (Figure 1). The technology blocks unfocused peripheral light rays while allowing focused light rays to converge and reach the retina through a central 1.36mm aperture. The result for the patient is continuous functional vision from near to far.

With the IC-8 IOL, surgeons can have greater confidence that they can reliably provide more patients with continuous, uninterrupted vision

Figure 1. The IC-8 small aperture IOL

Multifocal or trifocal lens designs can have pronounced peaks and valleys. Instead, the IC-8 IOL provides uninterrupted functional vision over 3.00D of defocus. Typically, the lens is implanted monocularly in the nondominant eye, with a target postoperative refraction of -0.75D. The fellow eye is treated with a monofocal intraocular lens (IOL) targeted for emmetropia. Although the technique is applied in a mini-monovision like manner, the result should not be confused with traditional monovision achieved with bilateral monofocal IOLs. With the IC-8 IOL implanted, the nondominant eye gains near and intermediate vision while at the same time retaining excellent distance vision. The small amount of myopia maximises the visual benefit for the patient by shifting the flattened defocus curve more fully into the functional range. Patients maintain binocular vision and stereopsis.

CLINICAL DATA

In a prospective, multicentre trial of the lens comprising 105 patients, the mean achieved manifest refraction spherical equivalent in the IC-8 IOL eyes was -0.42D +/- 0.55 and 0.01D +/- 0.48 in the fellow monofocal IOL eye at six months. Monocular uncorrected vision at six months in the IC-8 IOL eye was 0.87 logMAR (20/23) for distance, 0.83 logMAR (20/24) for intermediate, and 0.66 logMAR (20/30) for near. Binocularly, 99%, 95%, and 79% of patients achieved 20/32 or better uncorrected distance visual acuity, uncorrected intermediate visual acuity, and uncorrected near visual acuity, respectively.¹ Additionally, the target-corrected defocus curve measured with 0.75D of myopia extended the range of functional near vision by an additional dioptre without loss of distance vision compared with the distancecorrected defocus curve.

Figure 2. Mean binocular uncorrected visual acuities.¹

The extended depth of focus offered by small aperture can provide visual benefits to any presbyopic patient. Additionally, due to the small aperture design, the IC-8 IOL compensates for up to 1.5D of astigmatism.^1,2 Because the lens is symmetrical, axis alignment is not necessary. These qualities make the IC-8 IOL particularly ideal for a wide variety of patients, including those with low to moderate amounts of corneal astigmatism as well as irregular astigmatism patients.^3,4

In addition to mitigating astigmatism, the pinhole principle also provides a broad range of functional vision for patients with complex corneas, tolerating as much as a 1.0D of deviation from the intended refractive target (Figures 2–4).¹ These patients often have few options for a solution that can maximise their range of vision and help overcome poor visual quality. In a study of visual performance, all patients receiving the IC-8 IOL maintained 20/40 or better visual acuity, even with refractive error ranging from +0.5D to -1.5D.^1,5

VERSATILE IN DIFFICULT SITUATIONS

Figure 3. Tolerance to deviations from intended target.¹

The IC-8 is another refractive tool in the kit for helping patients achieve their desired visual outcomes. Those with irregular corneas and/or irregular astigmatism stand to benefit greatly from pinhole technology. This includes patients who have had previous refractive surgery – who often have higher order aberrations – and keratoconic patients who frequently have decentered optical apexes. The IC-8 implant may be suitable for patients with post-LASIK ectasia or even peripheral scarring with a clear central visual axis.

Today’s available diffractive- and refractivebased bifocal, multifocal, and trifocal IOLs are excellent treatments for patients seeking spectacle independence. Their use however, is limited for patients who have had previous refractive surgery, other ocular pathology, and/or irregular corneal astigmatism.

Patients implanted with small-aperture technology may be more sensitive to posterior capsule opacification, so an earlier YAG capsulotomy may be indicated, (it is best to laser outside the cusp of the IC-8, so as not to pit the central lens). Patients will get the benefit of light entering the eye around the lens and allow for fundus examination.

Figure 4. Addressing corneal astigmatism.¹

CONCLUSION

The IC-8 IOL’s small aperture optics are beneficial for a broad range of patients, especially those with highly aberrated corneas, providing a higher overall quality of vision and a wider continuous range of vision than other available technology. The lens offers a chance to give postrefractive surgery patients a premium result with fewer visual side effects than what may occur with a multifocal or trifocal IOL. With the IC-8 IOL, surgeons can have greater confidence that they can reliably provide more patients with continuous, uninterrupted vision. The wide ‘sweet spot’ and straightforward implantation technique makes it a user friendly IOL to implant.

Dr Ravinder Singh is a cornea, cataract, and refractive surgeon, at Eye Specialists Newcastle, Australia. He graduated from Medicine at the University of Sydney and undertook ophthalmology training at the Sydney Eye Hospital. He then undertook a Cornea and Refractive Fellowship in the UK under Professor Harminder Dua in Nottingham, UK followed by an Oculoplastic Surgery fellowship with Dr Jane Olver in London, UK. In addition to private practice Dr Singh is a VMO and Unit Director for Ophthalmology at the John Hunter Hospital and Senior Lecturer in Ophthalmology at the University of Sydney. He may be reached at [email protected]. Dr Singh acknowledged no financial interest in the products discussed herein. 

References: 

1. 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 Jul;43(7):956-968. 
2. Ang RE. Small-aperture intraocular lens tolerance to induced astigmatism. Clin Ophthalmol 2018;12:1659-1664. 
3. Agarwal S, Thornell EM. Cataract surgery with a smallaperture intraocular lens after previous corneal refractive surgery; visual outcomes and spectacle independence. J Cataract Refract Surg. 2018;44(9):1150-1154. 
4. Barnett V, Barsam A, Than J, Srinivasan S. Small-aperture intraocular lens combined with secondary piggyback intraocular lens during cataract surgery after previous radial keratotomy. J Cataract Refract Surg 2018;44(8):1042-1045. 
5. 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 Dec;160(6):1176-1184.e1.