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A Fresh Approach to Multifocal Intraocular Lenses

2 CPD in Australia | 0.52G in New Zealand | 2 April 2018
High resolution image of PanOptix diffractive zones.

 

By Dr. Lewis Levitz

Published peer-reviewed evidence-based research finds multifocal intraocular lenses provide good distance, intermediate and near vision with less dependence on spectacles. Success requires careful patient selection, pre-operative counselling and ongoing post-operative care, which is best comanaged by the patient’s optometrist and ophthalmologist.

LEARNING OBJECTIVES

1. Understand the mechanism of action of the major types of presbyopia correcting lenses
2. Understand advantages in technology of presbyopia correcting IOLs; refractive vs diffractive technologies and hydrophilic acrylic vs hydrophobic acrylic material
3. Understand research bout the side effect profiles of presbyopia correcting IOLs compared with peer lenses and traditional technology such as monofocal IOLs.

When discussing the use of multifocal intraocular lenses (IOLs) one is reminded of Alan Saks’ comment in mivision last year: "optometrists are like elephants – they have long memories."1

The same is true for ophthalmologists. Multifocal IOLs were introduced in the early 1990s however early multifocal lens design resulted in suboptimal visual outcomes. Although these lenses have been extensively modified over the last 30 years, opinions can take a little longer to change.

The only way to get through the mist and fog of opinion and past prejudices is to be aware of the recent published peer reviewed evidence-based medicine. It is now time to take a fresh look at multifocal IOLs.

WHY THE HISTORICAL BAD RAP FOR MULTIFOCAL LENSES?

Early multifocal designs were based on refractive optics. Refractive IOLs achieve multifocality by the use of a series of annular rings of different power. Pupil size therefore, was paramount. Small pupils, common in older patients, essentially negate the effect of these lenses while large pupils are predisposed to photopsia.2

The aging lens loses the ability to compensate for corneal spherical aberration. This, combined with the presence of a cataract, leads to reduced visual acuity. The concept of adjusting for these changes was only introduced as recently as 2004 with so-called aspheric IOLs. These lenses have been shown to improve contrast sensitivity and enhance mesopic visual acuity in patients, improving on the historical outcomes and providing superior visual performance.3

A further development, which is key to the success and wider suitability of multifocal lenses, is the addition of stable and accurate toric correction. It is vital to accurately optimise uncorrected visual acuity following cataract surgery. This is even more essential when implanting multifocal IOLs. It is only recently that we were fully aware of the critical importance of astigmatism on patient satisfaction. Residual astigmatism of 0.75D has been shown to markedly reduce visual and quality of life parameters.4 Until the advent of toric multifocal lenses, the effective pool of suitable patients included only patients with minimal astigmatism. Toric multifocal lenses now allow patients with regular astigmatism access to these IOLs.

Advances in corneal mapping improve our ability to identify irregularities or conditions such as subclinical keratoconus, which preclude multifocal lens success. In the past, these patients might have slipped through and reduced both the accuracy of preoperative lens calculations, and the resulting vision.

Similarly, IOL formulae used to calculate the power of the lens required to optimise acuity in an individual patient have developed significantly over the past three decades. They are now capable of accounting for additional ocular variables, such as posterior corneal curvature, and to minimise residual astigmatism and tighten overall refractive outcomes.

Mild retinal conditions, such as epiretinal membranes, can have a disproportionate effect upon quality of vision, which is amplified in multifocal IOL patients. The introduction of OCT technology has significantly advanced the ability to pick up subtle disease ahead of IOL implantation, reducing the risk of degrading postoperative visual quality.

Each of these small steps taken together has improved our ability to deliver improved vision with regards to multifocal lenses.

BIFOCAL OR MULTIFOCAL IOL?

Until recently ’multifocal’ lenses were really ‘bifocal’ lenses with two focus points. The near focal point remained IOL dependent, based on the refractive add particular to that make/manufacture of lens. The use of multifocal IOLs with different near focal points to achieve a range of near and intermediate unaided vision has been used with reasonable outcomes. Recent evidence suggests that the range of clear vision may be better if a trifocal IOL is used, which offers three separate functional focal distances.5,6


GETTING TO THE ’TRUTH‘ IN THE PUBLISHED LITERATURE IS DIFFICULT

It is difficult to compare different designs of multifocal IOLs as they may have different near and intermediate points. Each study tends to use a different notation in reporting styles and have acuity targets at non-standardised distances. To make matters worse there is no consensus on which questionnaire should be used to measure patient satisfaction, or the severity of photic symptoms. Even if there was a uniform patient satisfaction survey, there is no standardised test for near visual acuity. There is also no agreement on whether one should measure visual acuity or reading speed and whether this should be completed uniocularly or binocularly.3


PROS AND CONS OF AVAILABLE IOLS

In 2018, surgeons have a range of options available for their patients including accommodating, extended depth of focus and multifocal IOLs. Monovision remains a steadfast alternative supported by some surgeons.

Until 2016, the divide between surgeons offering multifocal intraocular lenses versus those proposing monovision was wide and acrimonious. A Cochrane review published in June 2016 has now given us some real answers and dispensed some myths.7 Patients with monovision as a planned visual outcome after cataract surgery had equal near and distance visual acuity to those having multifocal lenses implanted but were more likely to wear spectacles to fully correct astigmatism, or provide for near vision. Patients with multifocal IOLs experienced more glare or halos, which patients typically adapt to over time. Importantly there appeared to be no significant difference between distance vision in eyes with multifocal IOLs as compared to monofocal distance IOLs.7

Accommodative IOLs may provide a range of clear vision without the accompanying symptoms created by multifocal lens design. True accommodation is realised by minor changes in axial translation leading to a dynamic power shift enabling patients to obtain clear vision across distances. Literature however, suggests that current IOL models rely on pseudoaccommodative mechanisms which have resulted in variable results. Future design strategies may eventually offer more consistency, however at present these IOLs rarely represent the most appropriate option.8

Extended depth of focus (EDOF) IOLs typically use a form of diffraction grating to extend the focus range of the IOL while aiming to enhance contrast by limiting chromatic aberration. A recent comparison by Ruiz-Mesa et al. indicated that the EDOF IOL could provide similar intermediate and distance vision to the comparative trifocal IOL, however near vision was significantly better in the trifocal.9 There did not appear to be any difference in contrast sensitivity or higher order aberrations.

Collectively, these studies highlight the point that anyone offered a degree of optical independence following lens surgery needs to be counselled about the associated symptoms that may occur. These lenses are not suitable for patients who have unrealistic expectations or are unwilling to accept some sort of visual compromise in exchange for less dependence on glasses.

WHY THE PREFERENCES?

So, if the final vision and visual symptoms are similar, why do surgeons prefer one lens over another?

The distance at which a patient would like to read and work is important and can be used to customise a lens solution. The answer however is often dictated by other considerations, which are not obvious to the patient or optometrist, yet of cardinal importance to that particular surgeon. These would include the ease of insertion of the lens during surgery, familiarity with the implanting device and the speed at which the implant unfolds. How easy it is to explant is also a consideration for the surgeon. Lens stability post implantation and the incidence of posterior capsular opacification is also important as plate lenses have been shown to dislocate into the vitreous after laser capsulotomies. Each surgeon will weigh up what is most important to them and appropriate to their patient, then make a decision on the type of lens to be used.

Although there is a selection of good lenses, I will confine myself to the discussion of one particular diffracting trifocal lens, the PanOptix IOL.

THE PANOPTIX AND PANOPTIX TORIC TRIFOCAL IOL

The PanOptix is a hydrophobic IOL, using a non-sequential diffraction order to give simultaneous distance, intermediate and near focus.10

This all sounds very complicated, however the key features can be separated and their contribution  examined individually, which looks something like this:

  1. Diffractive lens
  2. Hydrophobic IOL
  3. Single piece acrylic lens
  4. Comfortable near (40cm) and reading/working distance (60cm)

Single-piece PanOptixTM toric intraocular lens with short-wavelength and UV-light filtering.


Refractive Versus Diffractive

The PanOptix IOL is a diffractive lens. Diffraction is the movement of light around an object or edge. In the PanOptix IOL, these edges are provided by ‘steps’ on the lens, which are designed to allocate light energy in different proportions to different focal points. This provides for clearer distance, intermediate and near acuity.

Historically, diffractive lenses have been shown to offer better optical quality with less photic phenomenon than refractive lenses.3,11 In comparison, and as stated earlier, refractive lenses are pupil dependent and therefore near vison is reduced with miosis. They also tend to have greater aberration, dependent on the pupil size.

Halos and glare occur in most patients with multifocal intraocular lenses including PanOptix, although they are known to diminish with time. Up to 15 per cent of patients will describe them as moderately annoying.12

High resolution image of PanOptixTM diffractive zones.

Hydrophobic IOL

Cases have been made for both hydrophobic and hydrophilic IOLs. Reportedly, hydrophilic IOLs have superior biocompatibility and less macrophage adhesion, which remains a possible advantage when a blood-aqueous barrier breakdown has occurred, such as in eyes with glaucoma or diabetes mellitus.13 Against this however, is an increased risk of posterior capsular opacification (PCO) compared with hydrophobic lenses.14 In their comparative review, Bai and co-authors found that hydrophilic IOLs had significantly increased rates of PCO following surgery compared to hydrophobic lenses regardless of optic edge design.15 PCO can easily be treated by Nd:YAG laser capsulotomy, however this intervention can lead to other complications, including a short-term increase in intraocular pressure, ocular inflammation, cystoid macular oedema and rarely, retinal detachment.16

The PanOptix IOL is hydrophobic, which means it is less inclined to opacify if it comes into contact with gas or air as it may occur after a vitrectomy. Hydrophobic lenses are also known to have better rotational stability in the bag, ensuring that the lens remains in the correct position, which is especially important in toric corrections.17

Single Piece Acrylic IOL

The PanOptix IOL is based on the existing acrylic monofocal IOL platform, which represents the most commonly used IOL in cataract surgery. This is important as the implantation process is both routine and familiar to the surgeon. In the unlikely event of IOL exchange, the lens can be removed without changing the surgeon’s preferred surgical technique

Comfortable Near and Reading Distances

The initial generation ‘multifocal IOLs’ (e.g. Alcon ReSTOR) provided surgeons with a range of near options from approximately 45cm to 54cm (3+ and 2.5+ respectively). IOL selection was based on patient requirements, for example, the older patient who required better near vision (reading books, playing cards) and who may not undertake significant night driving may have been more suitable to a higher power addition. Patients with more varied interests may have benefitted from integrating both IOL powers to provide a greater visual range. By providing clear vision at both 40 and 60cm however, the PanOptix IOL provides clear vision for patients demanding near vision while maintaining adequate vision for more intermediate tasks such as computer or tablet use.

VISUAL RESULTS

Recently, Carson and co-authors compared the optical performance of the three main trifocal IOLs. The authors showed equivalent or better performance in terms of image quality, resolution, and photic phenomena for the PanOptix IOL compared to the alternatives.10 Through-focus imaging showed a more even curve and thereby greater functional range between near and intermediate distances for the PanOptix IOL. The other IOLs did indicate improved modulation transfer function (i.e. potential vision) at 80cm, which may be better suited for a subgroup of patients.The surgeon can therefore, choose a lens based on each patient’s reading preference.

Recently, in a multicentre study of the PanOptix IOL from within our group, Lawless et al. confirmed the safety and predictability of the PanOptix lens and provided benchmark data.12 We found that 78.8 per cent of patients had vision of 6/6 or better, with mean uncorrected visual acuity of 6/6. Eighty-nine per cent had unaided vision of N6 or J2 for 60cm binocularly with 85 per cent achieving N4 or J2 binocular uncorrected vision for near. Five of the 33 patients reported moderate glare in the initial post-operative period before resolving.12 A larger study of 51 patients receiving bilateral PanOptix, presented at AUSCRS in 2017 from the same group (Reich et al.), showed that 94 per cent could see 6/6 or better and 90 per cent could read N6 or better uncorrected.18

Garcia-Perez et al. showed similar findings in a cohort of 116 eyes receiving the PanOptix IOL. Mean binocular uncorrected vision was 0.03LogMAR (equivalent to 6/6-1), 0.12 for intermediate and 0.02 for near distances. No difference in visual acuity was found between mesopic and photopic values. There was no requirement for spectacle correction reported for any activities by 94.8 per cent of patients.19

As recently as December 2017, in the American Journal of Ophthalmology, Kohnen and co-authors reported good unaided visual acuity at all distances leading to high patient satisfaction and spectacle independence at final follow up in a cohort of 27 patients receiving the PanOptix IOL. Although these patients all noticed glare when tested on a Quality of Vision questionnaire, 100 per cent said they would have the operation again or recommend it to a friend or relative.20 The same group was able to present an expanded cohort at the European Society of Cataract and Refractive Surgeons (ESCRS) in October 2017. In this nonrandomised cohort of 143 patients at six months, the mean binocular defocus curve demonstrated uncorrected vision of 6/7.5 or better through near (40cm) to intermediate (60cm) distances, highlighting an extended range of excellent unaided vision.21 At the same conference, Moore et al. echoed these findings with 85 per cent of their PanOptix cohort reporting complete independence from optical aids.22

As discussed previously, these results are possible with the PanOptix if care is taken to ensure the absolute majority of eyes are within 0.5D of post-operative spherical equivalence. If the patient has astigmatism, then the PanOptix Toric lens allows a greater number of patients access this technology and optimised visual outcomes.

COMPARATIVE DATA

Monaco and co-authors recently compared the PanOptix trifocal IOL with an EDOF IOL (Symfony IOL) and monofocal comparison. The authors found that both ‘multifocal’ IOLs provided good intermediate distance vision, however the PanOptix lens appeared to provide greater benefits for patients with near vision requirements. There were no differences in terms of binocular contrast sensitivity under either mesopic or photopic conditions or between photic phenomena between the PanOptix and EDOF IOL. As expected, both the PanOptix and the EDOF IOL had a higher incidence of halos and glare compared to the monofocal option, which confirmed the need for preoperative counselling and patient selection.23 Ruiz-Mesa and co-authors compared the optical performance of the PanOptix and Symfony IOLs. The Defocus curve confirmed a greater range of vision for the PanOptix trifocal IOL with significantly better vision from 50cm.9 Similarly, in a comparison of the PanOptix IOL with a combination of a standard monofocal and EDOF IOL (blended combination) results confirmed use of the PanOptix IOL resulted in better unaided near and intermediate vision than the comparative group.24

Comparing the PanOptix IOL to another diffractive trifocal IOL (FineVision), Gunderson and Potvin found that both IOLs provided excellent unaided visual acuity across distance, intermediate and near ranges. Comparing Defocus curves between IOLs, the authors found that the FineVision IOL performed better at -1.0D vergence (~ 80cm) however the PanOptix IOL was dominant at both -1.5D and -2.0D vergences (~60cm and 45cm respectively). This difference was confirmed in both unaided and corrected visual acuity assessment at 60cm. There was no perceived difference in quality of vision measures.25 The authors concluded that both IOLs remained an excellent option for motivated patients although the range of unaided vision of the PanOptix IOL may represent a more appropriate distance to people who routinely use tablets or other handheld devices. In a further comparative study, Perez-Cambrodi et al. recently found that the PanOptix IOL may provide more predictable refractive results compared to the FineVision IOL although the sample size was relatively small. The authors concluded that both IOLs continued to provide excellent functional vision at all distances.26

Böhm et al. presented a three month comparison between the PanOptix trifocal IOL and the Zeiss AT-Lisa tri 839MP IOL. There were no differences between the IOLs for both corrected or uncorrected visual acuity at all distances albeit intermediate readings were undertaken at 60cm for the PanOptix and 80cm for the At-Lisa models respectively. In both groups, all patients remained spectacle-free at distance however a small difference in total independence at near was found in favour of the PanOptix IOL (95 per cent vs. 90 per cent). This is likely to reflect the positioning of the focal points of the IOLs and again suggests that the PanOptix IOL may be preferred by those with closer vision requirements.27

In 2018, Escandon-Garcia compared the through-focus vision performance of the PanOptix and FineVision trifocal lenses with the Symphony extended depth of field lens. Although this was a small study, it showed that the trifocal lenses performed significantly better at near and distance than the extended depth of field lens without having more dysphotopsia.28

CONCLUSION

IOL technology, indeed cataract surgery, has come a long way in the last 30 years. Surgeons are capable of consistently achieving more accurate outcomes. This has allowed for the introduction of trifocal lenses, which provide good distance, intermediate and near vision with less dependence on spectacles.

The PanOptix IOL is stable in the bag, has a low posterior capsular opacification rate and gives good distance vision in most lighting conditions. It has a comfortable reading distance of 40cm and an intermediate reading distance of 60cm, making it appropriate for the needs of specific patients who read and use computer screens regularly. In addition to the technology, the success of multifocal lenses is found in careful patient selection, pre-operative counselling and ongoing post-operative care. In optimising these aspects, comanagement between the optometrist and ophthalmologist is essential, and can have a significant impact on patient adaptation and satisfaction. Optometrists who have a detailed history and understanding of patients’ personal habits and visual needs are well placed to identify those who may be suited to and benefit from multifocal IOLs. Managing patient expectations prior to surgery is essential, as is knowledge of the optics of the specific lens implanted. This allows for accurate postoperative refractions in the long term.

Ongoing evaluation of the vision and ocular health of multifocal patients by the optometrist plays a vital part in ensuring a happy satisfied patient with the best possible vision – which is of course the aim for both ophthalmologists and optometrists alike.

 

       Dr. Lewis Levitz practices from the Vision Eye institute in Camberwell, Blackburn South and Coburg, Melbourne. He has reviewed articles on cataract surgery for the Journal of Cataract and Refractive Surgery, Clinical and Experimental Ophthalmology and the Asia Pacific Journal of Ophthalmology. He also presents annual papers and audits at the Australian Society of Cataract and Refractive surgical meetings. He has an interest in oculoplastic surgery having completed a Fellowship in Cardiff, Wales.  
 

References
1. Saks A. Mivision. Satisfying difficult patients. Mivision 2017;125:45-46
2. Braga-Mele R, Chang D, Dewey S, et al. Multifocal intraocular lenses: relative indications and contraindications for implantation. J Cataract Refract Surg. 2014 Feb;40(2):313-22.
3. de Vries NE, Nuijts RM. Multifocal intraocular lenses in cataract surgery: literature review of benefits and side effects. J Cataract Refract Surg. 2013 Feb;39(2):268-78.
4. Wolffsohn JS, Bhogal G, Shah S. Effect of uncorrected astigmatism on vision. J Cataract Refract Surg. 2011 Mar;37(3):454-60.
5. Vilar C, Hida WT, de Medeiros AL, et al. Comparison between bilateral implantation of a trifocal intraocular lens and blended implantation of two bifocal intraocular lenses. Clin Ophthalmol. 2017 Aug 1;11:1393-1397.
6. Bilbao-Calabuig R, González-López F, Amparo F, et al. Comparison Between Mix-and-Match Implantation of Bifocal Intraocular Lenses and Bilateral Implantation of Trifocal Intraocular Lenses. J Refract Surg. 2016 Oct 1;32(10):659-663.
7. de Silva SR, Evans JR, Kirthi V, et al. Multifocal versus monofocal intraocular lenses after cataract extraction. Cochrane Database Syst Rev. 2016 Dec 12;12:CD003169
8. Pepose JS, Burke J, Qazi MA. Benefits and barriers of accommodating intraocular lenses. Curr Opin Ophthalmol. 2017 Jan;28(1):3-8.
9. Ruiz-Mesa R1, Abengózar-Vela A1, Ruiz-Santos M1. A comparative study of the visual outcomes between a new trifocal and an extended depth of focus intraocular lens. Eur J Ophthalmol. 2017 Sep 8:0. doi: 10.5301/ejo.5001029. [Epub ahead of print]
10. Carson D, Xu Z, Alexander E, et al. Optical bench performance of 3 trifocal intraocular lenses. J Cataract Refract Surg. 2016 Sep;42(9):1361-1367
11. Zelichowska B, Rekas M, Stankiewicz A, et al. Apodized diffractive versus refractive multifocal intraocular lenses: optical and visual evaluation. J Cataract Refract Surg. 2008 Dec;34(12):2036-42.
12. Lawless M, Hodge C, Reich J, et al. Visual and refractive outcomes following implantation of a new trifocal intraocular lens. Eye and Vision, 2017;4(1), 10.
13. Miyake K, Ota I, Miyake S, Maekubo K. Correlation between intraocular lens hydrophilicity and anterior capsule opacification and aqueous flare. J Cataract Refract Surg. 1996;22(Suppl1):764-769.
14. Li Y, Wang J, Chen Z. Effect of Hydrophobic Acrylic versus Hydrophilic Acrylic Intraocular Lens on Posterior Capsule Opacification: Meta-Analysis. PLoS One. 2013;8(11): e77864.
15. Bai L, Zhang J, Chen L, Ma T, Liang H-C. Comparison of posterior capsule opacification at 360-degree square edge hydrophilic and sharp edge hydrophobic acrylic intraocular lens in diabetic patients. International Journal of Ophthalmology. 2015;8(4):725-729. doi:10.3980/j.issn.2222-3959.2015.04.15.
16. Karahan E, Er D, Kaynak S. An Overview of Nd:YAG Laser Capsulotomy . Medical Hypothesis, Discovery and Innovation in Ophthalmology. 2014;3(2):45-50.
17. Bauer NJC et al, Astigmatism management in cataract surgery with the AcrySof toric intraocular lens, In Journal of Cataract & Refractive Surgery, Volume 34, Issue 9, 2008, Pages 1483-1488, ISSN 0886-3350
18. Reich JA. The Alcon PanOptixTM lens: Head to head session.21st Annual Congress AUSCRS, 3 August 2017 19. García-Pérez JL, Gros-Otero J, Sánchez-Ramos C, et al. Short term visual outcomes of a new trifocal intraocular lens. BMC Ophthalmol. 2017 May 17;17(1):72.
20. Kohnen T, Herzog M, Hemkeppler E, et al.Visual Performance of a Quadrifocal (Trifocal) Intraocular Lens Following Removal of the Crystalline Lens. Am J Ophthalmol. 2017 Dec;184:52-62.
21. Kohnen T. Multicenter defocus curve evaluation of a novel trifocal presbyopia-correcting IOL – 6 month postop results. Poster XXXV European Society for Cataract and Refractive Surgeons annual meeting, Oct 7, 2017: Lisbon, Portugal.
22. Moore J. Visual outcome and subjective experience after bilateral implantation of trifocal IOLs. Presentation XXXV European Society for Cataract and Refractive Surgeons annual meeting, Oct 8, 2017: Lisbon, Portugal.
23. Monaco G, Gari M, Di Censo F, et al. Visual performance after bilateral implantation of 2 new presbyopia-correcting intraocular lenses: Trifocal versus extended range of vision. J Cataract Refract Surg. 2017 Jun;43(6):737-747.
24. de Medeiros AL, de Araújo Rolim AG, Motta AFP, et al. Comparison of visual outcomes after bilateral implantation of a diffractive trifocal intraocular lens and blended implantation of an extended depth of focus intraocular lens with a diffractive bifocal intraocular lens. Clin Ophthalmol. 2017 Oct 26;11:1911-1916.
25. Gundersen, K.G, Potvin R. Trifocal intraocular lenses: A comparison of the visual performance and quality of vision provided by two different lens designs. Clinical Ophthalmology.2017 11, 1081–1087.
26. Perez-Cambrodi R. Comparison of the visual function and the intraocular aberrometric profile after cataract surgery with implantation of two different models of trifocal diffractive intraocular lenses. Presentation XXXV European Society for Cataract and Refractive Surgeons annual meeting, Oct 8, 2017: Lisbon, Portugal.
27. Böhm M. Comparative analysis of visual performance after bilateral implantation of two novel diffractive trifocal intraocular lenses following lens removal. Presentation XXXV European Society for Cataract and Refractive Surgeons annual meeting, Oct 8, 2017: Lisbon, Portugal.
28. Escandón-García S, Ribeiro FJ, McAlinden C, et al. Through-Focus Vision Performance and Light Disturbances of 3 New Intraocular Lenses for Presbyopia Correction. J Ophthalmol, vol. 2018, doi:10.1155/2018/6165493

' Ongoing evaluation of the vision and ocular health of multifocal patients by the optometrist plays a vital part in ensuring a happy satisfied patient... '