For many years cataract surgery was framed almost entirely as a restorative procedure. The goal was straightforward: remove the cloudy lens and replace it with a clear one, restoring distance vision and allowing the patient to function comfortably with reading glasses.
That model still applies to the majority of patients treated within the NHS, and it remains highly effective. However, the expectations of many patients have changed, especially those who previously underwent laser refractive surgery or who lead visually demanding professional lives, often arriving with a clear question: can I reduce my dependence on glasses after cataract surgery? Answering that question requires a different type of conversation.
During my ST2 rotation at an independent surgical centre in the Northeast of England, I began to see how this broader decision making process unfolds in practice. Under the supervision of Consultant Qasim Mansoor, I saw patients being considered for trifocal lenses, while others were advised against them following a more detailed preoperative assessment than I had previously encountered. It also made me realise how broad the modern intraocular lens (IOL) landscape has become, with over 100 models described globally – an area where trainees often have limited exposure during training [1].
A brief historical perspective
The story of IOLs begins with Sir Harold Ridley, who performed the first implantation at St Thomas’ Hospital in 1949 [2]. Ridley had noticed that fragments of polymethyl methacrylate (PMMA) from aircraft cockpit canopies, lodged in the eyes of RAF pilots during the Second World War, caused surprisingly little inflammatory response. This observation prompted the idea that a synthetic lens might be tolerated inside the eye.
The early decades of IOL implantation were challenging. Rigid PMMA lenses required large incisions and complications were not uncommon. Nevertheless, the principle proved sound and technological developments gradually refined both the surgical technique and the implants themselves.
The introduction of phacoemulsification allowed cataracts to be removed through much smaller wounds, while foldable silicone and acrylic lenses enabled implantation through incisions of only a few millimetres [3]. Modern hydrophobic acrylic lenses with square edge optics subsequently became the dominant platform due to their favourable rates of posterior capsular opacification [4].
"For resident doctors in training, understanding IOL options requires more than knowledge of lens formulas or surgical technique"
Even today, material properties remain clinically relevant. In clinic it is not unusual to encounter patients many years after surgery with subtle visual disturbances related to ‘glistenings’ within the lens optic [4]. Such observations serve as reminders that IOL design continues to evolve.
The main categories of intraocular lenses
Although the term ‘premium lens’ is widely used, it is not a particularly helpful clinical descriptor. A clearer way to approach modern IOLs is to consider the optical principle each design uses to extend or modify the range of vision.
Monofocal lenses
Monofocal IOLs remain the most widely implanted lenses worldwide [5]. They provide a single focal point, usually optimised for distance vision. Patients typically require spectacles for near tasks after surgery.
Most modern monofocal lenses are aspheric, incorporating negative spherical aberration to partially compensate for the cornea’s natural aberration profile. In practical terms this tends to produce slightly improved contrast sensitivity and image quality compared with older spherical designs [6].
For many patients, particularly those with ocular comorbidities, monofocal lenses continue to offer the most predictable visual outcomes.
Enhanced monofocal lenses
Enhanced monofocal lenses have emerged in recent years as an intermediate option between traditional monofocals and multifocal technology. Through subtle optical modifications they extend the depth of focus slightly, providing modest improvements in intermediate vision while maintaining a visual profile similar to standard monofocal lenses [7].
These lenses can be particularly useful for patients who would appreciate some additional functional range but are either unsuitable for multifocal implants or reluctant to accept the possibility of dysphotopsia.
Toric lenses
Corneal astigmatism is present in a significant proportion of cataract patients. Toric IOLs incorporate cylindrical correction within the lens optic in order to neutralise this refractive error.
Successful outcomes depend heavily on accurate alignment of the lens with the steep corneal meridian. Even small degrees of rotation reduce the effectiveness of the correction, meaning that careful preoperative planning and intraoperative positioning are essential [8].
Multifocal/trifocal lenses
Multifocal lenses achieve spectacle independence by splitting incoming light into multiple focal points. Earlier designs provided two focal distances, typically near and distance.
More recent trifocal lenses add an intermediate focal point, addressing the visual range used for tasks such as computer work or reading a dashboard display.
The optical trade off is unavoidable: dividing light between several focal points reduces contrast sensitivity and can produce visual phenomena such as halos or glare [9]. Although many patients adapt over time, careful counselling and patient selection remain essential.
Extended depth of focus lenses (EDOF)
EDOF lenses aim to create a continuous range of vision rather than discrete focal points. Different technologies achieve this through diffractive optics, refractive zone manipulation, or wavefront shaping designs.
In clinical practice these lenses often provide excellent distance and intermediate vision with fewer dysphotopsias than traditional multifocal implants [10]. However, patients may still require reading glasses for very fine print.
For individuals who spend substantial time using screens or who frequently drive at night, EDOF lenses can represent a useful compromise.
Light adjustable lenses
One of the more recent developments in cataract surgery is the light adjustable lens [11]. After implantation, the refractive outcome can be modified using controlled ultraviolet light treatments that reshape the lens material.
This approach allows surgeons to refine the postoperative refraction before permanently locking in the final refractive plan. It is particularly useful in patients who have previously undergone corneal refractive surgery, where conventional biometric calculations can be less predictable.
Making sense of IOL nomenclature
Classifying IOLs has never been straightforward. Lenses have been grouped by how they work optically, by how many focal points they produce, or simply by what surgeons and manufacturers chose to call them, with little consistency between centres or countries. The revision of ISO 11979-7 in 2024 brought some order to this, introducing simultaneous vision IOLs as a formal overarching category. The ESCRS Functional Vision Working Group went further, proposing a six-category classification built around what lenses actually deliver for patients rather than how they are engineered, dividing lenses into partial and full range-of-field groups based on the defocus curve. For trainees encountering this terminology for the first time, that shift in thinking from design to function is worth holding onto [12].
Contraindications to premium IOLs
- Irregular corneal astigmatism (keratoconus, dystrophies, post-refractive ectasia)
- Significant higher-order corneal aberrations such as coma or trefoil and spherical aberrations
- Uncontrolled or significant dry eye disease
- Macular pathology: epiretinal membrane, age-related macular degeneration (AMD), diabetic maculopathy, significant glaucomatous field loss
- History of uveitis or chronic intraocular inflammation
- Unrealistic expectations, or a patient who is psychologically unsuited to the neuroadaptation process.
The importance of preoperative assessment
While modern IOL technology is impressive, outcomes remain highly dependent on careful patient selection. During my rotation, one of the most striking differences compared with routine NHS cataract pathways was the depth of preoperative assessment performed for patients considering premium lenses.
Biometry remains the foundation of IOL power calculation. Optical biometers such as the IOLMaster 700 provide precise measurements of axial length, keratometry and anterior chamber depth. However, accuracy depends on a stable tear film, and unreliable readings are frequently encountered in patients with untreated dry eye disease [13]. For this reason, optimisation of the ocular surface before finalising lens calculations was emphasised repeatedly in clinic.
Corneal topography and tomography were also used routinely when assessing candidates for toric or multifocal implants. These investigations help identify irregular astigmatism or early ectatic disorders that could compromise visual quality.
Macular optical coherence tomography (OCT) forms another important part of the assessment. Even mild macular pathology may limit the benefits of multifocal optics, and identifying such conditions early allows surgeons to guide patients towards more appropriate lens choices.
Counselling and consent
For EDOF and multifocal lenses, the following points should be discussed in depth with the patient, in addition to the standard cataract surgery consent:
- Spectacle independence is the goal, but it is not guaranteed for all tasks
- Halos and glare are common initially and often improve, but do not always resolve fully
- Neuroadaptation typically occurs over three to six months. In rare cases can take longer
- A small proportion of patients find dysphotopsia intolerable enough to request explantation
- For private patients, there is an additional financial cost. This should be explained without pressure.
Matching the lens to the patient
Despite the growing sophistication of modern IOL technology, the most important element of lens selection often remains the consultation itself. During premium IOL discussions surgeons frequently begin by exploring a patient’s daily visual demands. Questions about reading habits, computer use, and night driving often provide more useful guidance than biometric data alone.
Some patients are highly motivated to reduce their reliance on spectacles and are willing to accept the possibility of halos or other visual phenomena. Others prefer a simpler solution and are comfortable continuing to use reading glasses.
Recognising these preferences early in the consultation helps ensure that the final choice aligns with the patient’s expectations.
Lessons from NHS and independent sector practice
Experiencing both NHS and independent sector cataract services during training highlights the strengths of each environment. Both NHS and independent sector practice involve high surgical volumes and the management of cataract in patients with a range of ocular comorbidities. For patients who express an interest in greater spectacle independence, consultations involve more detailed discussions about refractive targets and the possible use of advanced IOL technologies.
Rather than viewing these settings as fundamentally different models of care, it may be more helpful for trainees to see them as complementary educational experiences. Exposure to both perspectives provides a deeper understanding of how modern cataract surgery can be tailored to individual patient needs.
Conclusion
Cataract surgery continues to evolve as both a restorative and refractive procedure. While monofocal lenses remain the appropriate choice for many patients, advances in IOL design now allow surgeons to tailor visual outcomes more closely to individual lifestyles and preferences.
For resident doctors in training, understanding IOL options requires more than knowledge of lens formulas or surgical technique. It also involves appreciating the broader clinical judgement that underpins lens selection.
As the range of available technologies continues to expand, developing that judgement will become an increasingly important part of cataract training.
TAKE HOME MESSAGES
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Patient selection: the success of advanced IOL technology depends heavily on patient selection. Careful assessment of the cornea, macula and ocular surface is essential before considering multifocal or EDOF implants.
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Expectation management: patient expectations are just as important as optical design. A technically perfect procedure can still result in dissatisfaction if expectations are unrealistic.
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Early exposure: trainees benefit from early familiarity with the expanding range of IOL technologies. even brief exposure to premium lens consultations can provide valuable insight into the reasoning behind lens selection.
References
1. Stern B, Gatinel D, Nicolaos G, Grise-Dulac A. Intraocular lens models: Ecological distribution footprint and usage trends at a large ophthalmology centre. Eye (Lond) 2025;39(11):2260–8.
2. Henahan S. A second look at the first IOL implantation. Eurotimes 2025 [online]:
https://escrs.org/channels/eurotimes-articles/
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3. Gurnani B, Kaur K. Phacoemulsification. StatPearls. Treasure Island, Florida; StatPearls Publishing; 2026.
4. Nanavaty MA. Hydrophobic versus hydrophilic acrylic intraocular lenses within public sector based on the type of funding contacts: the debate continues. Eye (Lond) 2023;37(18):3712–3.
5. Hu JQ, Sarkar R, Sella R, Murphy JD, Afshari NA. Cost-effectiveness analysis of multifocal intraocular lenses compared to monofocal intraocular lenses in cataract surgery. Am J Ophthalmol 2019;208:305–12.
6. Deshpande R, Satijia A, Dole K, et al. Effects on ocular aberration and contrast sensitivity after implantation of spherical and aspherical monofocal intraocular lens - A comparative study. Indian J Ophthalmol 2022;70(8):2862–5.
7. Mencucci R, Morelli A, Cennamo M, et al. Enhanced monofocal intraocular lenses: a retrospective, comparative study between three different models. J Clin Med 2023;12(10):3588.
8. Nemet AY, Reitblat O, Levy A, et al. Clinical Outcomes following toric intraocular lens implantation: a case series study. J Clin Med 2025;14(7):2316.
9. Queiroz MFN, Ferreira FQT, Shimoda G, et al. Visual acuity, contrast sensitivity, and quality of life after bilateral implantation of multifocal diffractive intraocular lens. Arq Bras Oftalmol 2023;86(4):301–7.
10. Kanclerz P, Toto F, Grzybowski A, Alio JL. Extended depth-of-field intraocular lenses: an update. Asia Pac J Ophthalmol (Phila) 2020;9(3):194–202.
11. www.tamarawysemd.com/
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12. Ribeiro F, Dick HB, Kohnen T, et al. Evidence-based functional classification of simultaneous vision intraocular lenses: seeking a global consensus by the ESCRS Functional Vision Working Group. J Cataract Refract Surg 2024;50(8):794–8.
13. Jiang Y, Chen X, Gao Y, et al. Impact of tear film stability on corneal refractive power measurement and surgical planning for cataract. Adv Ophthalmol Pract Res 2025;5(2):100–6.
[All links last accessed June 2026]
