Maximising Presbyopia Correction with Extended Depth of Focus IOLs

Since as early as the 1940s, eye care specialists have harnessed the ocular concept of pinhole optics. Small aperture technology can improve vision for presbyopes, with and without cataracts, using advanced approaches that reliably extend depth of focus and reduce lowerand higher-order aberrations.

with the IC-8 small aperture IOL and Symfony EDOF IOLs, I can reinforce the patient’s range of vision while at the same time, the combination might reduce the visual effects of dysphotopsias

THE IC-8 IOL

AcuFocus’ IC-8 IOL has been designed to use the principles of small aperture optics to correct presbyopia. The implant consists of an opaque mini-ring made of polyvinylidene fluoride and carbon nanoparticles embedded into a single-piece aspheric monofocal hydrophobic acrylic lens (Figure 1). The IC-8 IOL collimates central light to extend the depth of focus, while at the same time blocking unfocused peripheral light rays. The focused light rays are allowed to converge, reaching the retina through a central 1.36mm aperture. Patients can enjoy functional vision that is in a continuous range, from near to far.

Unlike a multifocal implant, an IOL based on the small aperture principle has the ability to produce high quality, full-range vision without blurry zones and achieve increased tolerance for refractive error misses. For example, a deviation of more than 0.50D from the intended refractive target can result in a loss of one or two lines of vision with a typical monofocal or multifocal IOL. Similarly, in an irregular cornea, multifocality can result in poor visual quality and photic phenomena. Instead, a small aperture design is more forgiving of refractive errors – something that can be helpful in those patients where errors in biometry preoperatively may lead to the target refraction not being achieved, especially in cases where corneal irregularities and biometry errors, such as in dry eyes, may be a factor.

Where multifocal or trifocal lens designs can have pronounced peaks and troughs, the IC-8 IOL provides uninterrupted functional vision over 3.00D of defocus (Figure 2).¹ 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 IOL targeted for emmetropia. 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.¹ 

More Customised Visual Outcomes 

To enhance postoperative visual acuity, surgeons are starting to explore pairing the IC-8 IOL with other premium implants such as multifocal, a low-add multifocal, or other extended depth of focus lenses. By combining competing technologies, surgeons can minimise the side effects and enhance the sharpness of vision at near, intermediate and distance.

Figure 2. When the IC-8 eye is corrected to -0.75 and the monofocal eye is corrected to plano, patients achieve 3.00D
of continuous functional range of vision

MY EXPERIENCE

I have implanted 31 patients bilaterally with the IC-8 IOL in one eye and the Tecnis Symfony EDOF IOL (Johnson & Johnson Vision Care) in the other. The mean age of patients in this group before the surgery was 74.4, with a range from 62 to 90 years. The targeted residual refraction was -0.75D for the IC-8 eyes and -0.25D for the Symfony eyes. The visual outcomes measured at the last postoperative visit were uncorrected distance, intermediate and near vision, as well as manifest spherical equivalent.

In terms of uncorrected distance visual acuity (UCDVA) at the last visit, 86% and 83% IC-8 IOL and Symfony IOL eyes respectively, achieved 6/6 or better. When measured binocularly, 100% of patients achieved 6/6 or better UCDVA. For uncorrected intermediate visual acuity (UCIVA) at their last visit, 36% and 27% of IC-8 IOL implanted eyes and Symfony IOL 72 eyes, respectively, achieved 6/6 or better. When measured binocularly, 73% of patients achieved 6/6 or better UCIVA. Finally, with regard to uncorrected near visual acuity (UCNVA) at the last visit, 86% of IC-8 eyes and 71% of Symfony eyes achieved N6 or better. Binocularly, 92% of patients achieved N6 or better (Figures 3, 4, 5).

Figure 3. Monocular and binocular uncorrected distance visual acuity at the last post-op visit.

Using this implant strategy with the IC-8 small aperture IOL and Symfony EDOF IOLs, I can reinforce the patient’s range of vision while at the same time, the combination might reduce the visual effects of dysphotopsias associated with the Symfony EDOF technology. There is no loss of stereopsis with this approach and it is very well tolerated by patients.

In my experience, one additional benefit in using the IC-8 lens is that it can compensate for, or tolerate up to, 1.50D of preoperative corneal astigmatism. In the above patient group, contralateral implantation of an IC-8 IOL with a Symfony EDOF IOL provided excellent uncorrected near and distant visual acuity, even in the presence of clinically significant astigmatism of up to 1.46D of preoperative corneal astigmatism in the eye implanted with the IC-8 lens.

ADDITIONAL DATA

At the 2018 European Society of Cataract and Refractive Surgeons (ESCRS) meeting, Prof Gerd Auffarth presented experience with a similar approach, pairing the IC-8 IOL with the Lentis Mplus MF 20 IOL.² He reported five months of data showing patients’ visual outcomes were:

• Mean UCDVA = -0.05 (6/6)
• Mean UCIVA = 0.01 (6/6)
• Mean UCNVA = 0.14 (6/9)

Prof Auffarth also shared that patients experienced low level symptoms of glare and halo – similar to those experienced with monofocal IOLs.

BILATERAL SMALL APERTURE APPROACH

Bilateral IC-8 IOL use is increasing in normal and irregular cornea patients. Prof Burkhard Dick and colleagues authored the first published case series of bilateral IC-8 IOLs in normal eyes, finding that bilateral implantation improves range of vision versus contralateral IC-8 IOL and monofocal IOL implantation.³ The patients had better intermediate and near vision, with 100% 6/7.5 or better UCDVA, 83% 6/7.5 or better UCIVA and UCNVA at six months.

surgeons are finding that more patients are interested in having bilateral IC-8 IOL implantation, especially those patients who have highly aberrated eyes

Adjust Based on Outcomes 

Globally today, most patients still receive the IC-8 IOL lens in one eye with a monofocal implant in their fellow eye. However, surgeons are finding that more patients are interested in having bilateral IC-8 IOL implantation, especially those patients who have highly aberrated eyes. In order to preserve the bilateral option for patients, it is important to treat their first eye with an IC-8 IOL. Set the expectation with the patient that he or she will receive a monofocal implant in their second eye. Then, prior to surgery on the second eye, ask if he or she prefers to have the IC-8 IOL implanted in their second eye or stay with the original plan of receiving a monofocal IOL. This allows the patient to participate in the decision more meaningfully and receive the vision he or she wants.

Figure 4. Monocular and binocular uncorrected intermediate visual acuity at the last post-op visit

Other Examples 

For patients previously dissatisfied with their range of vision in their first eye after implantation with a monofocal IOL, the IC-8 IOL can be an excellent option to enhance their range of vision without the limitations of monovision. The IC-8 IOL can also be a great option for patients previously implanted with a multifocal or an EDOF lens in their first eye, who are dissatisfied with their result, complaining of dysphotopsia in their first eye, or for those who had a refractive surprise. I have used the IC-8 IOL successfully to treat these types of patients. I find the 3.00D of continuous range of vision provided by the small aperture IOL fills in the gaps in vision that exist in their first eye, while mitigating dysphotopsia at the same time.

CONCLUSION

The IC-8 IOL can be implanted with a variety of IOLs to help patients achieve a full range of vision. Today, the majority of patients globally are implanted contralaterally with an IC-8 IOL and a monofocal IOL. In my experience however, mixing and matching an IC-8 IOL and Symfony IOL provides cataract patients with excellent extended depth of focus from near to far, reduces halo and glare, and is very well tolerated. Bilateral application of the IC-8 IOL is also increasing, and more data will be forthcoming with regard to how visual outcomes can be improved with this approach.

Figure 5. Monocular and binocular uncorrected near visual acuity at the last post-op visit

As Prof Dick has noted, the IC-8 IOL has provided good visual outcomes in post- LASIK and post-RK eyes.³ These patients are motivated to maintain spectacle independence after cataract surgery, but many consider them unsuitable candidates for presbyopia-correcting IOLs. Small aperture IOLs are very tolerant of refractive surprise, a benefit 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 corneal scars, iris damage, or corneal irregularities by reducing aberrations. Overall, I have found the IC-8 IOL to be an extremely versatile tool for helping patients achieve their visual goals after cataract surgery.

Dr Christopher Chan FRANZCO, graduated at Monash University and trained in ophthalmology at the Sydney Eye Hospital followed by a fellowship at Monash Medical Centre. He is trained in all areas of general ophthalmology and has special interests in glaucoma management, cataract surgery and laser refractive surgery. Dr Chan has been actively involved with advanced technology multifocal and extended depth of focus IOLs. He was part of the early group of eye surgeons that implanted accommodating IOLs in Australia and was involved in a nationwide clinical trial of the new generation small aperture IOL in Australia and New Zealand. Dr Chan is involved in supervising ophthalmology registrars’ operations. He is a consultant at Western Health and past consultant at Royal Victorian Eye & Ear Hospital and Southern Health. 

References 

1. 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. doi: 10.3928/1081597X-20180716-02. 
2. https://www.healio.com/ophthalmology/cataractsurgery/ news/online/%7B2809ee76-e466-43fe-b70bdd94ff661925% 7D/video-edof-iol-using-pinhole-effectlessens- ocular-effects. 
3. Dick HB. Small-aperture strategies for the correction of presbyopia. Curr Opin Ophthalmol. 2019;30(4):236-242. doi: 10.1097/ICU.0000000000000576.