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Modern Presbyopia Correcting IOLs

2 CPD in Australia | 1G in New Zealand | 27 March 2017

By Adele Jefferies and Dr. Nick Mantell

Presbyopic patients increasingly ask about the power of multifocal IOLs to dramatically improve quality of life. A clear understanding of the options available, the patient selection process, and patient management pre- and post-surgery will enable you to enter into an informative discussion.

As optometrists we spend time every day guiding patients through their corrective options. For many patients we do this over a significant period of their life, as their refractive needs, ocular health and life in general, change. We aim to provide information and recommendations which not only improve the clarity of their vision, but also make it as functional as possible.

Presbyopes often require the most guidance. It may be the first time they’ve required visual correction, or after many years with a stable refraction, things are changing in a way they weren’t expecting. Fortunately, we have many great options available but all have benefits and compromises. Ideally, to make recommendations we should know not only the patient’s eyes, but their interests, occupation and lifestyle.

We all use single vision, occupational and progressive lenses, monovision and multifocal contact lenses and sunglasses for these patients in varying and often complimentary ways. From a functional perspective, multifocal options are often the patient’s preference both in anecdotal reports and the literature.1 Corrective options that balance the need for vision at all distances are becoming more important to our patients, and therefore so are the conversations to our patients about these options. 

Another normal occurrence in everyday optometry practice, that can be rather concerning for our patients, is the development of cataracts. This is an aspect of practise in which our established rapport and experience with our patients plays a key role in providing them with information and guidance about expected outcomes and pre- and post-operative expectations, thereby enhancing the care of the patient collaboratively with their ophthalmologist. We are often the referrer to ophthalmology for treatment, and as the patient sees it, the bridge at the beginning of the journey to improving their vision via lens extraction. At a recent one-day conference for orthoptists in Sydney, a Melbourne cataract/refractive surgeon commented that “cataract surgery provides a once in a life-time opportunity to improve quality of life”.

In a private referral setting, like discussing single vision vs. multifocal spectacles or contact lenses, we can also be proactive in discussing monofocal, monovision and multifocal intraocular lens options (IOL). This is not only in the patient’s interest of knowing all their options but also enhances the collaborative care of that patient.

Understanding Multifocal IOL Technology

Understanding multifocal IOL technology is the first step to being able to provide good advice to patients.

Like all aspects of refractive correction, IOL technology has continued to advance since the first ‘multifocal’ IOL was trialled in the 1981 with Hoffers split optic bifocal lens. Compared to monofocal IOLs, multifocal IOLs were designed to increase the depth of field, enhance near and intermediate vision, and reduce spectacle dependence.2 Lens designs for presbyopic correction for both distance and near vision include monovision, accommodative and multifocal IOLs.

The benefits and limitations of monovision are well understood and those who have a history of successful monovision contact lens wear may be the best suited for this modality of IOL. Accommodative IOLs, to date, have had limited success.3 Multifocal IOLs offer the best solution for patients wanting to be spectacle independent – they can be refractive or diffractive in design. Diffractive designs can be further differentiated into bifocal, trifocal or extended range optics.

The literature supports multifocal IOLs for those wanting less spectacle dependence, providing patients with functional distance, near and intermediate vision without glasses. However, all multifocal IOLs have the compromise of being associated with varying degree of halos and glare, and reduced contrast sensitivity.2,3,4

Clinical experience and the literature tells us that glare and halos will reduce with time, and that although contrast sensitivity is reduced compared with individuals with monofocal IOLs, it is generally within the normal range of contrast in age-matched phakic individuals.3

Optical Designs – Refractive vs. Diffractive 

Multifocal IOLs are designed to have two or more focal points, and therefore retinal images, resulting in what is termed simultaneous vision.3

Refractive

Refractive lenses are based on the principle that refraction results in a change in direction of the light ray due to a change in the optical density of the material transmitting the light ray.3 A key limitation to refractive lens designs is poor near vision, even when reading in good light. In terms of contrast sensitivity refractive designs appear to give either similar or greater reduction, compared to diffractive designs.3 The Oculentis segmental bifocal is the most modern of these designs which has been widely used in Europe and is now being used by some surgeons in Australasia.

Diffractive

Diffractive designs are based on diffractive principles – light that encounters a discontinuity or edge in the material in which it travels scatters in numerous directions, so light energy arriving at an edge or discontinuity can therefore be divided over two or more focal points.3 Diffractive multifocal lenses were patented in 1993 and used Fresnel lens optics.

Modern diffractive IOL designs incorporate aspheric optics to improve visual clarity and reduce halos and glare.3 Other advancements include combined refractive-diffractive designs, toric designs and variable additions. Using lower near additions compared to early designs has increased visual acuity at intermediate distance.3

Optical Designs – Bifocal vs Trifocal 

The earlier designs of multifocal IOLs all used bifocal optics for distance and near vision and therefore left a ‘gap’ in intermediate vision. Striving for a balance between the modern presbyope’s distance, near and intermediate needs has led to further advancements. Refractive designs are still using bifocal optics.

Trifocal diffractive IOLs were proposed to increase intermediate visual acuity compared to bifocal designs.3 Modern trifocal diffractive lenses use constructive interference from near and distance focal points to create an intermediate focal point without any further loss of light or decreased contrast sensitivity. These optical design features have resulted in decreased halos and glare when compared to the bifocal diffractive lenses.

The success of modern trifocal multifocal IOL outcomes has been supported by the literature. Carballo-Alvarez et al (2015) found that distance visual outcomes of trifocal lenses were similar to that of monofocal lenses; near vision outcomes resembled those of bifocal diffractive designs; improvements in intermediate vision were noted and trifocality did not lead to an increase in visual discomfort compared to bifocality.5

Nuijts et al (2015), when comparing bifocal and trifocal multifocal IOL designs, noted 80 per cent of trifocal IOL patients had spectacle independence compared with only 50 per cent of the bifocal IOLs, with no difference in quality of vision, perceived glare or halos between the IOL types.6

Extended Focus Lenses

The Symfony presbyopia lens uses diffractive bifocal optics to expand the depth of focus compared to a standard monofocal lens. The reading vision is not as good as with a trifocal lens.7

Trifocal Lenses

Trifocal diffractive IOLs have now effectively replaced bifocal diffractive IOLs. Trifocals provide better and more usable range of vision and are associated with less halos and glare. Both the Zeiss and Bausch & Lomb diffractive trifocal IOLs have been available for some time. The latest technology is Alcon’s AcrySof IQ PanOptix which has been available in the Australian and New Zealand market since late 2015 in spherical designs, and in toric designs since March 2017.

PanOptix is made of a hydrophobic, ultraviolet– and blue light– filtering material, mimicking the light transmission of a healthy human crystalline lens.2 AcrySof IQ PanOptix incorporates patented Enlighten Optical Technology, resulting in higher light transmission (88 per cent) than other trifocals,8 and is designed to improve quality of image and contrast sensitivity. With quadfocal optics, it offers patients a full and seamless range of uncorrected vision, including a wide range of comfortable near to intermediate vision (40 to 80cm) with a crisp focal point at 60cm.2 Other trifocal designs have crisp focal points at 40 and 80cm with a dip in vision around 60cm.2 The PanOptix design is beneficial as Occupational Safety and Health Administration (OSHA) recommend 60cm for comfortable computer work.9,10 Carson et al (2016) laboratory simulations on the lens found that this second-generation trifocal IOL showed equivalent or better performance in image quality, resolution, and photic phenomena compared with two first-generation trifocal IOLs.2

Centration of the lens. Image supplied by Dr Phil McGeroge, WA showing the centration and toric alignment achieved with the first PanOptix Toric implanted in Australia

The theoretical defocus curve for AcrySof IQ PanOptix shows uninterrupted vision from near through to intermediate distance with a range of vision from 35cm to 80cm8

PanOptix IOL

 

Achieving Plano: the Key to Success

New research in IOL calculation has increased surgeons’ ability to achieve their refractive targets. 

For any IOL implantation the refractive outcome is important. This is particularly true for presbyopia correcting IOLs where patients are expecting maximum spectacle independence. For spherical refractive error, achieving an outcome +/- 0.5D or less is considered to be industry standard and most surgeons feel that astigmatism should also be 0.5D or less.

Excellent biometry is essential to achieving a good outcome. The introduction of optical measurement of axial length has been one of the most significant improvements in the last decade.

Over time multiple IOL formulae have been developed to help us predict the appropriate IOL power. These formulae vary in the way they account for the difference between the curvature of the front and back surfaces of the cornea as well as predict the effective lens position post-surgery.

Studies have shown that the more recent Olsen and Barrett formulae are the most accurate for predicting the correct IOL power.11 At Eye Institute we routinely use the Barrett Universal II formula for this reason.

It is also recognised that consistent formation of the capsulorrhexis at time of surgery in terms of diameter, circularity, and centration is likely to improve the predictability of the refractive outcome. There is some soft evidence that the accuracy of capsulorrhexis created by a femtosecond laser may improve this.

Toric IOLs have revolutionised the treatment of astigmatism at the time of surgery. The correction of astigmatism is based on the total corneal astigmatism rather than refractive astigmatism. We can measure corneal astigmatism with a variety of instruments. Unfortunately they all measure something slightly different and so deciding which value to use for IOL calculation can be confusing. We now recognise corneal topography is very helpful, as refractive outcomes are more predictable if the corneal astigmatism is regular and symmetrical. It is also helpful to exclude Forme fruste keratoconus, and pellucid marginal degeneration as these patients may not be suitable for a Toric IOL.

Our understanding of corneal astigmatism has also improved dramatically. Koch et al reminded us that the effect of posterior corneal astigmatism can impact appropriate correction prediction.12

Barrett’s has incorporated the effect of the posterior cornea in his calculator. A 2015 study demonstrated that by taking the corneal curvature measurements from the Lenstar biometer and using the Barrett toric calculator resulted in the greatest reduction of post-operative astigmatism (p <0.021). The predictability was also very good using the IOL master biometer corneal measurements.13

Finally the alignment of the axis of the Toric IOL has become more sophisticated and accurate at the time of surgery. It is recognised that there is a degree of cyclotorsion of the eyes when going from sitting to lying. If this is not accounted for then it will lead to misalignment of the toric IOL. The most common method to take this into account is to mark the patient’s eyes while sitting prior to surgery. However it is becoming more common to use technologies like Alcon’s Verion system to obtain more accurate and consistent alignment. This system takes preoperative measurements while the patient is sitting up. It then interfaces with the operating microscope providing a real time overlay image via the microscope eye pieces. This image tracks movement of the limbal blood vessels to adjust real time for both cyclotorsion and eye movements enabling more accurate Capsulorhexis formation, toric alignment, and lens centration.

Lens design can also impact the alignment of the IOL post-operatively. Hydrophobic platforms like the Alcon AcrySof material allow for adhesion to the posterior capsule, not only lowering the rate of posterior capsular opacification but also post-operative lens decentration and rotation.14,15 The most commonly used trifocal IOLs, Zeiss AT-LISA and the Bausch & Lomb FineVision are both designed on hydrophillic platforms. The latest Alcon PanOptix is designed on the AcrySof IQ hydrophobic platform.

Patient Selection

As with any form of surgery, a complete pre-operative ocular assessment is essential prior to recommending a presbyopia correcting lens. We are particularly interested in identifying any corneal abnormality, macular pathology or tear film abnormality preoperatively.

The refraction is important. Hyperopes tend to be more tolerant of presbyopia correcting IOLs than emmetropes, or myopic patients particular for purely refractive patients who are undergoing clear lensectomy. This is less critical if BSCVA is already reduced due to cataract. This does not mean that emmetropes and myopes are not suitable for presbyopia correcting IOLs, however they will require significantly more discussion regarding expectations and outcomes.

All these patients should ideally have corneal topography. This helps exclude mild forms of keratoconus, and pellucid marginal degeneration, and will identify any irregular astigmatism. These patients are not good candidates for a presbyopia correcting IOL.

Many optometrists today have access to advanced diagnostic technology. Although the decision about suitability for multifocal IOLs should ultimately remain with the ophthalmologist, optometrists can play a significant role in identifying who a good or poor candidate might be and by providing support by setting realistic expectations about their potential suitability prior to referral.

Lens Material – Clear vs. Blue-light Filtering

The effect of blue light exposure to a patient’s ocular health has been discussed at length in the literature. With increased use of computer screen and artificial lighting, growing numbers of blue light filters are becoming available for patients from spectacle lens coatings to computer screen covers.

The normal optical transmission through the human eye to the retina is limited by the cornea and the lens. The cornea filters wavelengths below 300nm and in young patients the crystalline lens filters wavelengths below 400nm essentially protecting the retina from UV light exposure.16 As the crystalline lens ages, it progressively attenuates the transmission of blue light (400-500nm). Filtering of light up to 480nm reduces intra-ocular light scatter and significantly enhances contrast sensitivity.16 It is hypothesised that this natural change in spectral transmission of the lens is a bioprotective mechanism to counteract for the decrease in melanin within the RPE with age (the protective pigment which absorbs short-wavelength light). A recent paper which evaluated the effect of blue light-filtering intraocular lenses (IOLs) on disease progression in a limited number of patients (n=27 eyes) with geographic atrophy (GA) concluded that “The clinical data strongly support a photoprotective role of blue light–filtering IOLs on the progression of the atrophic form of dry age-related macular degeneration after cataract surgery.”17 Further clinical studies are required to verify these findings.

Clear, UV filtering and blue-light filtering IOLs are available today. The Alcon AcrySof Natural IOL has been designed to provide light transmission similar to a 54 year crystalline lens without cataract.17 When comparing the visual performance of AcrySof Natural blue-light filtering material to the AcrySof UV filtering material contrast sensitivity with the AcrySof Natural is improved without impacting colour perception.16

Effective Co-management

As mentioned earlier, optometrists often play a key role in referral of patients for cataract surgery. Effective co-management of patients requires good communication, and this should begin with an informative yet efficient referral letter.

Optometrists are often in the position of having a long-term patient-practitioner relationship and as well as providing essential refractive, acuity and general and ocular health findings, may be able to provide information that assists good patient satisfaction post-surgery. Any information about occupation, hobbies and specific visual demands that would see a patient better suited for monofocal vs. monovision vs. multifocal lenses would be beneficial, as would any history of success or failure with monovision or multifocal contact lenses. If the patient expresses any specific interest in being spectacle independent for most visual tasks, or if they have any concerns regarding the options, these should also be noted.

As multifocal IOLs are associated with lower contrast sensitivity, any patients with decreased contrast sensitivity due to ocular pathology, such as macula disease or corneal dystrophies, are not ideal candidates, so these should be looked for and mentioned in the letter. Ideally include OCT results in your referral. Patients with very small pupils are also often not the best candidates, and neither are patients with strabismus or amblyopia due to the visual outcomes benefiting from good binocular summation.

Post-Surgery Management

Managing the first optometry examination after surgery will lay the foundation for successful ongoing patient care.

The first appointment following cataract surgery is often very pleasant. Patients are often very happy to have had the surgery, surprised with the brightness of their vision and grateful for your referral.

A good case history here is very important to gauge the patient’s satisfaction with their unaided vision, identify any tasks that may benefit from glasses, their level of adaptation to glare and halos, their need for sunglasses and their degree of dry eye symptoms. I find dry eye questionnaires useful in practice, such as the OSDI, to have a baseline for treatment success.

This appointment is also a good place to highlight what they can see, how much vision has improved at all distances, and to be optimistic and realistic about their unaided vision. Photic phenomena are among the most frequent reasons for dissatisfaction after multifocal IOL implantation.3 This makes the first post-surgery examination an important chance to remind them that visual results and awareness of glare and halos often continue to improve in the months following surgery, but that it will always be normal to be aware of halos to some degree with night driving.

When refracting these patients following surgery it is important to consider the unique optics that are now in the eye and the effect this has on testing. Auto-refractor results will not be helpful as the results will just reflect which section of the lens it happens to have measured through. End points on acuity charts may not be ‘crisp’ so avoid trying to add minus to make it crisp. You need to remember those basic principles of refraction, we want the maximum plus prescription for good visual acuity, only add minus to the distance refraction if it increases the number of letters seen. Determining if any additional near correction is needed is best done with a trial frame, beginning with low powered plus lenses.

If glasses would be beneficial for some tasks you will want to present this in a positive way to avoid the patient having a sense that the surgery was a failure. Again a balanced perspective is needed. Explain that the unaided vision they achieved is good and they can do most day to day tasks very well, but, for example for improved comfort for prolonged periods of near work or detailed near tasks they would benefit from reading glasses. Recording their unaided near visual acuity pre-op is helpful. This will enable you to remind patients, who may have increased their expectations since experiencing a new level of unaided vision, how much more flexibility they now have. You also need to discuss and communicate the need for ongoing ocular health and visual care with routine exams, despite their now reduced need for refractive correction.

Summary

Lifestyle changes and advances in IOL technology mean multifocal IOLs are increasingly part of common cataract and refractive surgery discussions and more patients are making pro-active enquiries. When used for the appropriate patients, multifocal IOLs can dramatically improve quality of life. It’s important to instil trust in your patients regarding your clinical knowledge, expertise and quality of patient care. Having open, informative conversations about all available treatment options is fundamental to this. If you want to engage more patients in conversations about presbyopia correcting IOLs, consider reaching out to your local cataract-refractive surgeon to discuss best co-management protocols. 

 

Adele Jefferies BOptom(Hons) CertOcPharm (Therapeutics) is an optometrist based in Auckland with special interests in contact lenses, ocular surface disease and therapeutics. She is also a Professional Teaching Fellow at the University of Auckland, a CPD Accreditation Committee Member for New Zealand Optometrists and Dispensing Opticians Board and a Clinical Masters Student at the University of Auckland. Ms. Jefferies is also a pre-market evaluator of contact lens, contact lens care solutions and dry eye care products for various companies. 

Dr. Nick Mantell MBChB, FRANZCO is an ophthalmologist with Eye Institute in Auckland, New Zealand.  During his career, he has worked in a number of important roles in both the private and public sector health care, including as an ophthalmology surgeon at Green Lane Hospital for three years. He has trained House surgeons, Registrars and Fellows at Green Lane Hospital. Dr. Mantell is a Clinical Senior Lecturer in ophthalmology at Auckland University and is actively involved in the ongoing teaching of optometrists. 

References
1. Jefferies A. Multifocal Contact Lenses: Why? How? And Modern Designs. mivision Sept 2016; 116: 53-57
2. Carson D, Xu Z, Alexander E, Choi M, Zhao Z, Hong X. Optical bench performance of three trifocal intraocular lenses. J Cataract Refract Surg 2016; 42:1361–1367
3. de Vries NE, Nuijts RMMA. Multifocal intraocular lenses in cataract surgery: Literature review of benefits and side effects. J Cataract Refract Surg 2013; 39:268–278 Daniel Carson, BS, Zaiwei Xu, MS, Elsinore Alexander, BS, Myoung Choi, PhD, Zeyu Zhao, BS, Xin Hong, PhD
4. Calladine D, Evans JR, Shah S, Leyland M. Multifocal versus monofocal intraocular lenses after cataract extraction - Review. Cochrane Database of Systematic Reviews 2012; 9.
5. Carballo-Alvarez J. Visual outcomes after bilateral trifocal diffractive intraocular lens implantation. Journal of Refractive Surgery 2015
6. Nuijts R. et al. Comparison of a trifocal intraocular lens with a D3.0 D bifocal IOL: Results of a prospective randomized clinical trial. Journal Cataract and Refractive Surgery 2015
7. Gatinel & Loicq. Clinically relevant optical properties of bifocal, trifocal, and extended depth of focus intraocular lenses. Journal of Refractive Surgery 2016
8. Alcon Laboratory Notebook:14073:77-78.
9. Charness N, Dijkstra K, Jastrzembski T, et al. Monitor viewing distance for younger and older workers. Proceedings of the Human Factors and Ergonomics Society 52nd Annual Meeting, 2008. www.academia.edu/477435/Monitor_Viewing_Distance_for_Younger_and_Older_Workers. Accessed April 9, 2015.
10. Average of American OSHA, Canadian OSHA and American Optometric Association recommendations for computer monitor distances.
11. Cooke DL, Cooke TL. Comparison of 9 intraocular lens power calculation formulas. J Cataract Refract Surg. 2016 Aug;42(8):1157-64.
12. Douglas D. Koch, MD. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg 2012; 38:2080
13. Abulafia, Barrett GD. Prediction of refractive outcomes with toric intraocular lens implantation. J Cataract Refract Surg. 2015 May;41(5):936-44
14. Farooqui et al. Management of moderate and 
severe corneal astigmatism with AcrySof Toric intraocular iens implantation – Our experience. Journal of Ophthalmology 2015
15. Morgan-Warren & Smith. Intraocular lens-edge design and material factors contributing to posterior-capsulotomy rates: comparing Hoya FY60AD, PY60AD and AcrySof SN60WF. Clinical Ophthalmology 2013
16. Bhattacharjee et al Visual performance: Comparison of foldable intraocular lenses. Journal of Cataract and Refractive surgery. 2006;32
17. Pipis et al. Effect of the blue filter intraocular lens on the progression of geographic atrophy. European Journal Ophthalmology 2015; 25 (2): 128-133
 Alcon Laboratories (Australia) Pty Ltd. Phone: 1800 224 153; NZ: Phone: 0800 101 106.NP4#

' Patients are often very happy to have had the surgery, surprised with the brightness of their vision and grateful for your referral '