The struggle between the scarcity of resources and the supplier-induced demand derived from the rapid pace of innovations in healthcare can be dealt with, at least partially, by prioritizing those technologies whose benefits are relevant for all stakeholders, primarily patients. This would imply broadening the conventional measurement of clinical endpoints, often derived from randomized controlled trials (RCT), identifying and evaluating patients’ preferences. The United Kingdom’s National Institute for Health and Care Excellence (NICE) was recently forced to reevaluate its choice to employ an endovascular intervention (EVAR) for an abdominal aortic aneurysm due to the failure to consider patients’ feedback into account (1, 2). Despite the initial negative recommendation based on RCT evidence and cost modelling (1), NICE accepted EVAR as a reasonable option for disease management in line with the perspective of the scientific community and patients, who expressed firm preferences for a minimally invasive approach (2). Unfortunately, the identification and measurement processes of relevant outcomes for patients and other stakeholders is a very complex task. In this context, the core outcome set (COS) represents a consensus-derived minimum set of outcomes that should be measured and reported in research regarding a specific disease or treatment (3, 4). A COS should identify selected outcomes that are relevant to key stakeholders, like patients, clinicians and, more in general, health service users, and should drive research in the direction of meaningful and standardized evidence generation.

COS are particularly useful in research fields where there is significant variation in the outcomes measured and reported or where there is a scarcity of data available on important patient outcomes such as quality of life, long-term parameters, patients’ preferences or economic aspects of treatments. A disease that recalls these characteristics is cataract, a common condition consisting of the clouding of the crystalline lens of the eye, causing a gradual but progressive decline in vision that cannot be corrected with glasses (5). If left untreated, it can result in total blindness (5). The only effective intervention to revert visual loss caused by cataract is the surgical removal of the natural opacified lens, to be replaced with an artificial intraocular lens (IOL). Cataract surgery has been estimated to be the single most common surgical procedure performed in high-income countries worldwide (6), as well as in the European Union (7). The range of IOL models now available has expanded spanning from standard to premium technologies differing in terms of attributes, pricing, and patient outcomes (8). Monofocal IOLs allow patients to focus at only one distance, and thus require patients to wear spectacles to compensate for the lack of progressive correction at different distances. Nonetheless, they avoid the unwanted optical side effects associated with multifocality (e.g., glare, starbursts and haloes), which might cause variable patient satisfaction (9, 10). Because of their lower cost, good distance vision performance, and favorable profile in terms of incidence of photic phenomena, monofocal IOLs currently represent the standard of care, being the most implanted type of lens due to their guarantee of functionality and reliability (11). More recently, a new generation of monofocal IOLs has been introduced. These IOLs are characterized by a safety profile comparable to standard monofocal IOLs but with an extended range of intermediate vision (11).

In the cataract context, the definition of a COS is underrepresented compared to other clinical fields (3). Moreover, current core outcome sets lack considering health outcomes as derived from real-world studies (12–16) and do not indicate what measurement units should be used to assess each of the outcomes included in the set. Moreover, none of the available COS has been specifically intended for the evaluation of IOLs’ performances. Therefore, our work further advances current COSs by identifying relevant outcomes as derived from real-world evidence and direct patients’ involvement, in addition to RCTs, and indicating the metrics to be used to assess each of the outcomes of the set for the postoperative evaluation of monofocal IOLs (both standard and new generation).

The development of a COS consists of four methodological steps (4). First, the scope of the COS should be clarified in terms of setting (e.g., routine care or research studies), health conditions, population and intervention addressed (17). The second step aims to check whether a new COS is needed. The third step relates to the protocol definition for the development of the COS; in this regard, the COS-STAP statement was followed, which suggests the definition of the scope of the COS, stakeholder involvement, COS development plans and consensus processes (18). The last step determines the application of the protocol to obtain a specific COS.

Developing and identifying technologies whose benefits are relevant to the healthcare ecosystem is crucial when prioritization is necessary to keep the healthcare systems financially sustainable. This is the principle of the value-based healthcare paradigm. Investments and market access authorization for medical technologies have often been based on clinical endpoints not necessarily relevant for end-users such as clinicians, patients and providers (24, 25). Determining what is truly crucial and for whom is therefore fundamental to guide developers’ focus on investing in technologies that are likely to deliver added value to stakeholders and decision-makers (e.g., regulatory and Health Technology Agencies bodies). This will help developers to identify innovations that can positively impact patients’ lives and the system as a whole. The use of COS has been developed to define the most relevant outcomes for all stakeholders. Although many institutions and organizations are supporting the development of relevant metrics, comprehensive and standardized identification of outcome sets has been lacking (26, 27). The COMET (Core Outcome Measures in Effectiveness Trials) initiative has started exploring the setting of clinical trials to guide the development, implementation, evaluation and updating of core outcome sets (4, 17, 18, 28). At present, considering cataract surgery, two core outcome sets have been published and are available in the COMET initiative database. Mahmud and co-authors (19) have proposed a core set of pre, intra, and post-operative measures for cataract surgery outcomes, applicable to all types of IOLs. The COS was developed through experts’ consensus, also including the perspective of a patient advocate. Subsequently, Evans et al. (20) have developed a core set by extracting and summarizing the main outcomes reported in published RCTs comparing multifocal and monofocal IOLs. Moreover, since 2012 the International Consortium for Health Outcomes Measurement (ICHOM) has started to promoting and facilitating the development of global sets of patient-centred outcome measures worldwide to create better value for all stakeholders (29). An ICHOM standard set has been proposed for cataract as well, but it does not include peculiar considerations about the IOLs performance or on the economic impact of the surgery (19). The present study aimed at developing a COS for cataract patients scheduled to standard or new-generation monofocal IOLs implantation, starting from a comprehensive literature search of reported outcomes and involving both ophthalmologists and patients. In line with current trends in health technology evaluation, which aim to compare treatment options based on patients’ preferences, patients’ input is essential for producing a COS that is as comprehensive as possible (30, 31). The literature provides examples of patient-important outcomes that were mistakenly left out when the COS was created without their participation. In the context of fibromyalgia (32), seven outcomes considered important by the patients like pain, stiffness, fatigue, sleep, patient and physician global assessment of improvement and tenderness, were not included in any of the 9 clinical studies assessed through a meta-analysis which considered clinical trials on treatment. Other important symptoms identified by the patients, such as cognition, depressive and anxiety symptoms, were not explored by most of those studies. Another example refers to rheumatoid arthritis, for which patients selected 63 treatment outcomes through in-depth interviews. Many of the 63 outcomes described as important are not currently included in the commonly used professional core sets (33). Also, in our study, ophthalmologists selected, as important, 11 outcomes which were all clinical and did not include any non-clinical outcomes, 4 of which were instead selected through the evaluation performed by patients, determining a final COS composed of 15 outcomes (see Supplementary Table S2 for the complete list of outcomes proposed for the COS). The inclusion of patients’ perspectives allowed us to broaden the analysis by considering aspects that matter to the final users of the technology. Moreover, concerning vision stabilization after cataract surgery, the timing for the evaluation of the main vision parameters proposed by the ophthalmologists (30 days) was in line with the perception of the patients (mean 34 days). Our study also suggested the measurement units for such parameters.

The present COS is an extension of previous works developed on the topic of IOLs. The search strategy was designed to identify all studies evaluating monofocal IOLs, including both single-arm and comparative assessments of monofocal IOLs against any other IOL type in both RCTs and observational studies. Indeed, the other published studies on COS development either started from the appraisal of the existing literature focused on RCTs only (20) or considered data collected through existing registries (19). Moreover, the present study actively involved patients in the assessment of key outcomes. In previous studies, the consensus on the COS was reached only among the authors of the publication (without the involvement of patients) (20) or through a group composed of clinicians and only one patient advocate (19). Visual acuity, contrast sensitivity, refractive errors, adverse events, and patients-reported quality of vision and quality of life (including spectacle independence) have been confirmed relevant for clinicians and patients like in the other published COS (19, 20). Nevertheless, our analysis pointed out the importance of assessing also clinical outcomes like aberrations and posterior capsule opacification, and patients’ reported outcomes like the ability to perform activities related to near vision without glasses and safety of movements.

Finally, while the proposed COS focuses on monofocal IOLs, it represents a valuable use case for the extension of the present study methodology to the evaluation of other devices in both ophthalmology and other disease areas.

In a context with limited healthcare resources, it is important to optimize their use considering also the preferences of end-users, namely patients. Moreover, the use of COS fosters cross-study comparability while discouraging selective outcome reporting, allowing for more effective data synthesis and comparison of the efficacy of different technologies. This, in turn, may increase the entire evidence base available to influence clinical practice, produce clinical guidelines, and make healthcare resource allocation choices (4), with benefits reaching throughout the healthcare system. The present study aimed at developing a core set of outcomes for the postoperative evaluation of monofocal IOLs for cataract surgery. The process, which involved both ophthalmologists and patients, showed the important role of the latter that allowed including patients’ reported outcomes, specifically quality and satisfaction in near vision without glasses, quality of life, safety of movements and reading ability. The proposed COS is intended to be measured and reported not only in clinical trials but also in clinical practice to increase the body of real-world evidence (39–41). In the case of comparative assessments, it would be crucial to also include cost-effectiveness outcomes to optimize the allocation of healthcare resources.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

The study involving humans was approved by Bocconi Ethics Committee, Bocconi University. The study was conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

RT: Conceptualization, Methodology, Supervision, Writing – review & editing. CR: Formal analysis, Investigation, Methodology, Project administration, Resources, Visualization, Writing – original draft, Writing – review & editing. AC: Formal analysis, Investigation, Writing – review & editing. IG: Formal analysis, Investigation, Writing – review & editing. LN: Formal analysis, Investigation, Writing – review & editing. MB: Investigation, Writing – review & editing. GC: Investigation, Writing – review & editing. EF: Investigation, Writing – review & editing. RM: Investigation, Writing – review & editing. LT: Investigation, Writing – review & editing. DT: Investigation, Writing – review & editing. RG: Investigation, Writing – review & editing, Supervision.