Cataract & Refractive Surgery: The Era of EDOF IOLs

Over the past 50 years there have been many advancements in the field of cataract surgery that have improved surgical outcomes. From the introduction of phacoemulsification by Charles Kelman in 1967, to the development of ophthalmic viscosurgical devices in the 70s, toric lenses in the 90s, and gradual improvements in biometry – all have improved the safety and accuracy of cataract surgery. Improvements in refractive outcomes related to these earlier advancements have enabled the development of different lenses to achieve optimum refractive outcomes for different patient groups.

Intraocular Lenses

The recent introduction of EDOF lenses has enhanced the options available to cataract and refractive surgeons. In contrast to multifocal IOLs, which tend to use refractive or diffractive optics to create several focal points, EDOF lenses elongate the focal point, thereby enhancing depth of focus. The optical design of EDOF lenses minimises the higher-order aberrations and chromatic aberrations that often plague multifocal lenses. By enhancing contrast sensitivity and reducing photic phenomena, EDOF lenses offer a more natural visual experience. EDOF lenses can’t yet provide the range of focus enabled by trifocal multifocal lenses, however they do maintain quality of vision. The development of modern EDOF lenses has catalysed a paradigm shift in how referrers, surgeons, and patients perceive the outcomes of cataract and refractive lens surgeries.

Monofocal IOLs

Monofocal lenses are designed to provide clear vision at a single fixed distance. By specifying a particular lens power in a given eye, either distance, intermediate or near vision may be targeted, generally at the expense of unaided vision over the remaining distances. In our practice, monofocal lenses continue to be the lens of choice among many of our patients – particularly those who are happy wearing multifocal or bifocal spectacles and patients with ocular pathology. And most of our monofocal patients continue to enjoy excellent vision following surgery.

Monofocal IOLs continue to offer the best contrast sensitivity and mildest aberration profile among available lenses. We see many patients with age-related macular degeneration (AMD), glaucoma, corneal pathology or ocular surface disease for whom we favour monofocal lenses. Similarly, patients who require prisms will continue to need spectacles after surgery and often do best with a monofocal IOL. These lenses certainly continue to provide excellent visual outcomes and are unlikely to be entirely replaced by newer EDOF technology.

Multifocal IOLs

Multifocal IOLs split light into multiple foci, which can be designed to achieve distance, intermediate or near vision. These lenses are designed to provide peaks of clarity at certain distances, depending on the optical design. Most modern multifocal IOLs are trifocal and use diffractive optics, which, although an improvement on older refractive technology, still causes a degree of dysphotopsia. Not every patient is suitable for a multifocal IOL, which leads surgeons to approach these lenses with a degree of caution. Nevertheless, for suitable patients who favour a high degree of spectacle independence, multifocal IOLs are often the best choice.

Extended Depth of Focus Lenses

The definition of an EDOF lens can cause confusion. Among those considered to be EDOF lenses there is some variability between the amount of intermediate vision that each of these lenses can achieve. From a practical perspective, many surgeons would consider an EDOF to be one that extends the depth of focus sufficiently to have good intermediate vision. That might typically be considered to include those lenses with intermediate vision equivalent to around +1.0 to +1.5D near add at the spectacle plane. In achieving intermediate vision, it is important to note that EDOFs should also provide continuous focus, rather than relying on a separate refractive or diffractive focal point to enhance intermediate vision.

The American National Standard and American Academy of Ophthalmology census statement,^1,2 which define EDOF lenses, makes a clear distinction between multifocal lenses and EDOFs on the basis that the latter must achieve extended focus without creating distinct focal points. Beyond that, provided bench testing and clinical studies show at least 0.5D improvement in depth of focus compared with monofocal controls, a lens may be considered an EDOF. From a clinical perspective however, it is useful to consider those lenses that provide only a small degree of extended focus as enhanced monofocal or monofocal plus lenses.

Thus, there are low intermediate focus EDOF lenses that we would call enhanced monofocals, such as the Tecnis Eyhance and the Rayner Enhanced Monovision (EMV). There are also EDOFs, as we might traditionally consider them, with about +1.0 to +1.5D of near add. This group includes the Alcon Vivity, Tecnis Symphony, Tecnis PureSee, ZEISS At Lara and Bausch and Lomb’s LuxSmart. In this group, by adherence to the American National Standards Institute definition, we would also include pinhole lenses such as the Bausch and Lomb’s IC-8. This is not an exhaustive list, but these lenses represent those most commonly used in the Australian market.

Extended Depth of Focus Lens Design

EDOF lenses may employ different optical designs. These may include diffractive, spherical aberration based, pinhole effect, and non-diffractive wavefront shifting technology (Table 2).

The first EDOF lens approved by the United States Food and Drug Administration (FDA) was the Tecnis Symfony. This lens was released in Europe and Australia in 2014 and became widely adopted. The Symfony uses a diffractive echelette design to elongate the focal length. This was a different approach to the two or three distinct focal lengths created by diffractive multifocal IOLs, however the use of an echelette still rendered some patients susceptible to glare, haloes, and starbursts.³

In 2019, Johnson and Johnson released the Tecnis Eyhance – which was classified as an enhanced monofocal lens – and later, in 2024, the Tecnis PureSee EDOF lens was introduced into the Australian market. This lens might be considered the successor to the Symfony lens. The PureSee is a refractive presbyopia-correcting lens designed to enhance visual performance across various distances. The curvature of the refractive surface of the lens has smooth transition zones, which allow light rays from different distances to converge. Quality of vision studies have demonstrated that this lens performs significantly better at near and intermediate distances than the Eyhance lens, with similar quality of vision.⁴ Head-to-head comparison of the PureSee with the Symfony lenses has not been done yet, but this will be useful to help determine the relative strengths of each of these Tecnis EDOF lenses.

The ZEISS At Lara uses a low add diffractive echelette design to provide a smooth transition between the distance and intermediate focal points. This is a similar design to the Symfony. The precise optics of these lenses have been debated in the academic literature. They are both generally considered to be EDOF lenses with continuous focus from distance to intermediate, however some authors suggest that the Symfony and At Lara may offer a distinct near refractive add akin to a low powered multifocal lens.⁵

The AcrySof Vivity was released in Australia in 2020. This lens has a unique design based on wavefront shifting technology. The central 2.2 mm of the lens contains two non-diffractive transition elements, which alter the wavefront to elongate the depth of focus.6 This novel mechanism is neither considered diffractive or refractive. Instead, subtle changes to the anterior surface stretch the wavefront, with studies confirming that this lens maintains similar quality of vision to a monofocal IOL.⁷ Originally, the Vivity lens was made with AcrySof, but in 2023 Alcon released the Vivity Clareon, which may provide better clarity of vision with reduced chance of forming glistenings.⁸

LuxSmart uses a combination of fourth-and sixth-order spherical aberrations within the central 2 mm zone to elongate the focal point. This allows for improved uncorrected distance and intermediate vision, with minimal visual disturbances like haloes or glare.9 The lens also features a smooth transition zone and an aspheric monofocal peripheral zone, providing a seamless range of vision.

The IC-8 Apthera lens features a central opaque mask with a 1.36 mm aperture, which blocks peripheral unfocussed light while allowing focussed central light to pass through. This pinhole effect reduces the impact of corneal irregularities and enhances image sharpness. The mask itself contains many microscopic perforations, which help to maintain peripheral vision. Surrounding the mask is an aspheric monofocal zone that ensures high-quality distance vision. These lenses may have a particular role in improving vison for patients with iris defects and corneal opacities or irregularity. Unilateral implantation in the non-dominant eye, in particular, provides good distance and intermediate vision.¹⁰

Among the enhanced monofocal lenses, the Rayner EMV uses positive spherical aberration design to provide a smoother transition between distance and near vision. The Eyhance has a progressive refractive surface that increases in power from the periphery to the centre of the lens.

Changing Patient Expectations

Five years ago, most of our cataract patients were offered single vision lenses. Occasionally a patient was motivated to be spectacle independent, and they were offered trifocal lenses or monovision, but the reality was that most cataract patients continued to need spectacles for all but distance vision.

Sydney Eye Surgeons’ journey toward the use of EDOF lenses began in 2019 when we were asked to participate in a study evaluating the real-world use of a new EDOF. Patient care has always been at the forefront of our surgical decisions, and in this regard, we tentatively started using this new technology.

The most important feature of any lens is that it should provide predictable refractive outcomes with minimal undesirable optical effects. It is well accepted that older presbyopia correcting IOLs induced some degree of positive dysphotopsia, but we were pleasantly surprised by the side effect profile of this new type of lens. As our use of different types of EDOF and EDOF-like lenses has continued, we have formed the view that these lenses provide a superior refractive outcome for many patients who may have previously been offered a monofocal lens alone. Patients undergoing cataract or refractive lens exchange surgery today are better informed and more demanding than ever. The advent of EDOF lenses enables surgeons to meet these expectations, particularly in terms of visual outcomes and lifestyle benefits.

Enhanced Visual Outcomes

Patients now anticipate a broader range of functional vision without the need for spectacles. EDOF lenses allow them to perform everyday tasks such as driving, cooking, and using digital devices with minimal dependency on glasses. Even if patients continue to use spectacles for reading a book, many are pleased to be able to perform most other tasks without glasses. The promise of reduced photic phenomena has also reassured many patients, who may have previously been hesitant, to opt for anything but a single vision IOL due to concerns about glare and haloes.

Lifestyle and Independence

Many cataract and refractive lens exchange patients are happy to continue to wear reading spectacles after surgery if their lifestyle does not involve much near work. Some simply want the ability to maintain an active and independent lifestyle post-surgery. EDOF lenses cater to this by providing a low risk of dysphotopsia with a high-quality visual experience that supports activities such as driving, swimming, outdoor activities, desktop computer use, and social engagement. This has broadened the appeal of cataract and refractive lens exchange surgery to a slightly younger cohort of patients who consider a degree of presbyopia correction to be an important surgical outcome.

Pre-operative Counselling and Investigations

Pre-operative counselling often begins with the referrer. Optometrists, in particular, have an important role in educating patients about different lens options and guiding them through the decision-making process for cataract and refractive surgeries. Many patients often come to their ophthalmic consultation with a good sense of these options, having been informed by their optometrist about the differences between monofocal, multifocal, and EDOF lenses.

This initial optometry consultation may include explanation of the benefits and limitations of each option, as well as some expectation setting regarding possible visual outcomes. Prior to the introduction of EDOF lenses only a small proportion of patients might have been considered candidates for any degree of presbyopia correction, whereas now such correction should be considered for many cataract patients. EDOF lenses, with their unique combination of advantages, have increased both the relevance and complexity of these discussions, necessitating a deeper understanding of these lens technologies among optometrists and ophthalmologists.

Many of our patients have had a longstanding relationship with their optometrist. This can be invaluable in understanding both the visual needs of a patient, their preference regarding post operative spectacle wear, and tolerance of dysphotopsias. Each of these factors is an essential consideration in deciding which lens to implant in a given patient. At Sydney Eye Surgeons, we value the input our optometrist referrers may have in lens selection and encourage them to share any recommendations they may have. The introduction of EDOF lenses has fostered stronger collaboration between optometrists and ophthalmologists, an outcome that has certainly benefited patients and improved satisfaction among referrers and surgeons.

Once a patient has consulted an eye surgeon, further considerations may come into play. The ophthalmologist should engage in a detailed preoperative consultation to ascertain the patient’s lifestyle and specific visual needs. Patient expectation, pre-operative visual acuity, ocular dominance, ophthalmic pathology, occupation, personality, and preoperative measurements may all be considered by the surgeon when choosing an IOL. Good communication between surgeons and their patients is essential. Patients often like to be well informed about lens options –they are likely to seek second opinions and conduct independent research, highlighting the need for comprehensive and transparent advice.

In addition to clear communication, the selection of EDOF lenses requires meticulous preoperative assessments, including evaluations of corneal topography, biometry, the ocular surface, and macular health. While preoperative features may contraindicate use of an EDOF lens in some patients, more commonly we identify patients who are unsuited to multifocal IOLs. Patients in this group would have formerly been offered only a single vision lens, which may have aligned poorly with their expectations and visual needs. EDOF lenses have broadened the pool of patients who can enjoy some degree of presbyopia correction and given these patients a viable alternative to multifocal IOLs.

Presbyopia Correction With EDOF Lenses

EDOF lenses offer several refractive options. Most of the more common EDOFs offer near vision consistent with a +1.00 to +1.5D add. The degree of near vision offered by a particular lens must be considered during the pre-operative discussion and planning. There are three basic refractive strategies suitable for correcting intermediate and near vision using an EDOF lens: the surgeon may target emmetropia in both eyes, aim for a myopic outcome to favour near vison, or use mini monovision or blended vision to target distance and intermediate vision in one eye and intermediate and near vision in the other.

Bilateral implantation of EDOF lenses, targeting emmetropia in both eyes, is the most common strategy we employ in our practice. Pre-operative counselling includes reiterating to the patient the need for reading spectacles following surgery. In addition to enjoying excellent distance vision, most patients who achieve emmetropia tend to be comfortable viewing a computer screen or their vehicle’s speedometer. Most read N10 unaided, which corresponds with reading a menu or phone with slightly enlarged print, while some have surprisingly good unaided reading vision and may require reading spectacles for very few tasks. Quality of vision tends not to be an issue, and patients do not report glare or haloes.

Although EDOF lenses used in this way are not a complete solution to presbyopia, they certainly resolve much of the frustration some people have with multifocal spectacles. Even in patients who do not achieve emmetropia though refractive surprise, EDOF lenses may enable clear reading and intermediate vision with a lower add than would otherwise be required, rendering multifocal spectacles a more comfortable option than possible if monofocal IOLs had been implanted.

The use of mini monovision to enhance near vision has proven particularly suited to EDOF lenses. Single vision lenses must be targeted at about -2.50 to allow small print to be read. This corresponds to an unaided distance vision of about 6/30 or worse, a significant sacrifice in distance vision, which to many patients is an unacceptable trade. Additionally, monovision with monofocal lenses often leads to good unaided distance and near vision, but patients may report blurred intermediate vision. EDOFs have transformed monovision to allow a seamless transition from distance and intermediate vision in one eye to intermediate and near in the other. Additionally, with some EDOFs, a residual refraction of -0.75 is sufficient for unaided reading vision. This enables patients to maintain uncorrected distance vision of around 6/9 in the reading eye – a much smaller sacrifice in distance vision than that necessitated by a monofocal IOL targeting near sight.

In the same way that monovision serves patients’ near vision needs while preserving adequate unaided distance vision, bilateral implantation of an EDOF lens targeting near vision is also well tolerated.

Conclusion

Cataract surgery has entered a new era with the advent of EDOF lenses, bridging the gap between monofocal and multifocal options. Unlike traditional IOLs, which either provide a single focal point or distinct near and distance vision zones, EDOF lenses enhance visual continuity by extending the depth of focus. This allows for improved intermediate vision while maintaining high contrast sensitivity and reducing visual disturbances such as haloes and glare.

The benefits of EDOF technology make it an attractive option for patients seeking greater spectacle independence, however, limitations still exist, as EDOF lenses cannot restore near vision to the level of multifocal lenses. Mini monovision using EDOF lenses can offer a degree of presbyopia correction similar to multifocal IOLs, but patient selection remains crucial, with individual lifestyle needs and visual expectations playing a significant role in determining the ideal refractive target and IOL choice.

As technology advances, the integration of hybrid designs, combining EDOF with refractive or diffractive elements, may further refine outcomes. Future developments in cataract surgery, including customised IOL solutions and enhanced optical modelling, will continue to optimise visual quality.

For now, EDOF lenses represent a significant milestone in the evolution of cataract surgery, offering a balance between presbyopia correction and quality of vision that patients have generally found very beneficial.

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Dr Robert McDonald BSc (Hons) BMed (Hons) MPH FRANZCO is a comprehensive ophthalmologist and specialist corneal, cataract, and refractive surgeon. He is the Director of Clinical Training and the Head of the Department of Cataract Surgery at Sydney Eye Hospital and holds academic appointments at both the University of Sydney and the University of Notre Dame. Dr McDonald is in private practice at Sydney Eye Surgeons.

Dr Alex Hamilton BMed MPHTM (Dist) FRANZCO is a cataract, refractive, and corneal surgeon and medical retina specialist. As a specialist corneal surgeon at Sydney Eye Hospital, Dr Hamilton trains Australian and international eye surgeons. He is a clinical lecturer at the University of Sydney and is in private practice at Sydney Eye Surgeons.

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