National Eye Institute Visual Function Questionnaire

Abstract

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The National Eye Institute Visual Function Questionnaire (NEI VFQ-25) is an internationally recognized, interviewer- or self-administered patient-reported outcome measure (PROM) engineered to assess vision-targeted health-related quality of life (HRQOL). Derived from the original 51-item survey, the 25-item core instrument (frequently supplemented with 12 optional items) measures the broad psychosocial, physical, and functional sequelae of visual impairment across diverse ocular pathologies, including cataracts, glaucoma, diabetic retinopathy, and age-related macular degeneration. The tool models visual impairment not merely as a sensory deficit, but as a disabling condition that restricts personal autonomy, social engagement, and psychological stability. Psychometrically, the instrument comprises 12 distinct subscales: General Health, General Vision, Ocular Pain, Near Activities, Distance Activities, Social Functioning, Mental Health, Role Difficulties, Dependency, Driving, Color Vision, and Peripheral Vision. Items are transformed onto a standardized metric from 0 to 100, where higher scores correspond to optimal visual functioning and well-being. A non-weighted composite score summarizes general vision-specific functioning by averaging 11 subscales, explicitly excluding the standalone General Health subscale. Validation across numerous language adaptations—including English, Italian, French, Turkish, Spanish, Japanese, Chinese, and Serbian—confirms acceptable to excellent internal consistency (Cronbach’s alpha ranging from 0.65 to 0.90+ for multi-item subscales) and temporal stability via intraclass correlation coefficients (ICCs generally exceeding 0.80). Construct and criterion validity are reinforced through multitrait-multimethod matrices and convergent correlations with generic HRQOL metrics, such as the Short Form-36 Health Survey, and clinical visual parameters (e.g., best-corrected visual acuity, visual field deficits). Modern psychometric evaluations utilizing Rasch analysis have illuminated structural idiosyncrasies, such as category threshold disordering and multidimensionality, prompting debates regarding the extraction of separate visual functioning and socioemotional constructs. The NEI VFQ-25 remains a gold-standard instrument in both ophthalmic clinical trials and longitudinal epidemiological studies.

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Keywords

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Visual Impairment, Health-Related Quality of Life, NEI VFQ-25, Patient-Reported Outcome Measure, Psychometrics, Ophthalmology, Construct Validity, Rasch Analysis, Visual Acuity, Cross-Cultural Adaptation, Cataract, Glaucoma, Age-Related Macular Degeneration

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Authors

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The primary developmental architecture of the National Eye Institute Visual Function Questionnaire was formulated by researchers affiliated with the RAND Corporation, the University of California Los Angeles (UCLA) School of Medicine, and the National Eye Institute (NEI):

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• Carol M. Mangione, MD, MSPH — Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.

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• Paul P. Lee, MD, JD — Department of Ophthalmology, Duke University Eye Center, Durham, North Carolina, USA (currently University of Michigan, Ann Arbor, Michigan, USA).

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• Peter R. Gutierrez, BA — RAND Corporation, Santa Monica, California, USA.

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• Karen L. Spritzer — Division of General Internal Medicine and Health Services Research, UCLA, Los Angeles, California, USA.

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• Sharon Berry, MA — RAND Corporation, Santa Monica, California, USA.

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• Ron D. Hays, PhD — Division of General Internal Medicine and Health Services Research, David Geffen School of Medicine at UCLA, and RAND Corporation, Santa Monica, California, USA.

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The cross-cultural psychometric validation for the Serbian adaptation referenced extensively herein was conducted by clinical investigators at the Military Medical Academy and the Faculty of Medicine, University of Belgrade:

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• Bojan Kovač, MD, PhD (Corresponding Author: [email protected]) — Eye Clinic of the Military Medical Academy, Belgrade, Serbia.

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• Miroslav Vukosavljević, MD, PhD ([email protected]) — Eye Clinic of the Military Medical Academy, Belgrade, Serbia.

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• Jelena Djokić Kovač, MD ([email protected]) — Eye Clinic of the Military Medical Academy, Belgrade, Serbia.

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• Mirko Resan, MD, PhD ([email protected]) — Eye Clinic of the Military Medical Academy, Belgrade, Serbia.

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• Goran Trajković, PhD ([email protected]) — Institute of Medical Statistics and Informatics, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

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• Janko Janković, MD, PhD ([email protected]) — Institute of Social Medicine, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

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• Milena Smiljanic, MD ([email protected]) — Institute of Medical Statistics and Informatics, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

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• Anita Grgurević, MD, PhD ([email protected]) — Institute of Epidemiology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

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Purpose

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In ophthalmology and visual science, objective diagnostic markers—such as high-contrast Snellen or Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, automated static perimetry mean deviation, and retinal nerve fiber layer thickness—frequently exhibit modest concordance with a patient’s subjective visual disability. Two individuals presenting with identical 20/40 Snellen visual acuity may experience vastly divergent functional limitations depending on illumination sensitivity, contrast attenuation, scotoma localization, and cognitive or vocational coping capacities. Generic health-related quality of life instruments, including the EuroQol 5-Dimensions (EQ-5D) or the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), typically lack the granular content sensitivity required to discern the specific day-to-day burdens precipitated by ophthalmic pathology. Consequently, therapeutic outcomes risk misinterpretation if restricted entirely to structural or physiological parameters.

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The NEI VFQ-25 was explicitly conceptualized and validated to bridge this clinical and psychometric divide. Its primary objective is to provide a standardized, psychometrically rigorous patient-reported outcome measure that translates the biological phenomenon of visual compromise into quantifiable metrics of visual ability, psychological distress, role limitations, and personal autonomy. The scale evaluates how chronic, vision-threatening pathologies—predominantly cataracts, age-related macular degeneration, glaucoma, and diabetic retinopathy—systematically compromise functional domains such as reading standard newsprint, recognizing familiar faces across a room, navigating environmental steps or curbs in dim lighting, executing close-range vocational tasks, and operating motor vehicles.

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Beyond its clinical descriptive utility, the NEI VFQ-25 serves three foundational applications in modern healthcare systems:

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• Clinical Trials and Regulatory Approval: Regulatory agencies, including the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA), routinely require validated PROMs as secondary or co-primary endpoints to verify that biomedical interventions (e.g., anti-VEGF intraocular injections, minimally invasive glaucoma surgeries, multifocal intraocular lens implants) yield meaningful functional enhancements in patients’ lives.

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• Health Economics and Cost-Utility Analysis: The scale enables health economists to map subjective visual preservation and rehabilitation onto utility metrics, justifying the cost-effectiveness and resource allocation of novel ophthalmic therapies within national healthcare infrastructures.

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• Routine Longitudinal Monitoring: In clinical practice, administering the questionnaire provides a standardized mechanism for identifying early functional decline, covert depressive symptoms, or unexpressed dependencies that standard clinical consultations fail to detect, thereby facilitating timely referrals for low-vision rehabilitation, psychological counseling, and occupational therapy.

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Psychological Construct

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The core construct evaluated by the NEI VFQ-25 is vision-targeted health-related quality of life (HRQOL). Rather than treating vision as an isolated sensory input, this construct operationalizes visual functioning as an interactive multidimensional nexus comprising biological, functional, affective, and sociocultural dimensions. Visual impairment generates downstream functional disruptions that systematically restrict daily activities, induce secondary emotional strain, attenuate perceived personal control, and compel reliance upon external caregiving systems. The scale operationalizes this multidimensional framework across 12 discrete subscales:

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• General Health (1 item): A solitary self-rated health item evaluating the respondent’s subjective perception of their overall biological health status, serving as an anchored benchmark to contrast systemic somatic comorbidities against ocular-specific burdens.

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• General Vision (1 item): A global, qualitative rating of the participant’s functional eyesight when utilizing habitual visual corrections (spectacles or contact lenses), capturing perceived sensory adequacy ranging from excellent to functionally blind.

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• Ocular Pain (2 items): Captures both the temporal frequency and the functional interference produced by physical symptoms localized in or around the ocular globes, including burning sensations, persistent itching, aching, or acute intraocular discomfort.

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• Near Activities (3 items): Measures task-specific difficulty in executing central, high-resolution tasks requiring fine near-focal convergence, including deciphering standard printed newsprint, performing precise handiwork or needlecraft, and locating objects within a dense, visually cluttered shelf.

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• Distance Activities (3 items): Evaluates functional visual capability over intermediate and distance horizons, assessing the capacity to read navigational and street signs, distinguish facial expressions or identify acquaintances across distance, and negotiate physical obstacles (e.g., stairs, curbs) under conditions of reduced ambient illumination.

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• Social Functioning (2 items): Assesses the degree to which visual limitations restrict interpersonal communication, reciprocal social engagement, participation in communal events, and the capacity to accurately interpret nonverbal conversational cues and reactions from others.

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• Mental Health (4 items): Quantifies visual-specific psychological distress, encompassing ruminative worry regarding disease trajectory or impending blindness, generalized frustration regarding visual limitations, feelings of diminished self-efficacy, and depressive symptoms precipitated by ocular morbidity.

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• Role Difficulties (2 items): Captures structural limitations in occupational performance, hobby engagement, or home management, specifically focusing on reduced productivity and restricted task duration caused directly by visual dysfunction.

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• Dependency (3 items): Operationalizes the erosion of self-reliance, gauging the involuntary reliance upon external agents (family, peers, or social services) for daily tasks, reliance on proxy verbal communications, and confinement to the home environment.

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• Driving (2 items / conditional skip logic): Evaluates complex visuo-motor functioning under diverse environmental challenges, evaluating the subjective difficulty of daytime driving in familiar territories, navigation in low-light/nighttime environments, and vehicle operation during adverse weather conditions or high-density traffic congestion.

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• Color Vision (1 item): Assesses the functional integrity of cone photoreceptor-mediated chromatic discrimination, specifically measuring difficulty in differentiating, picking out, and matching garments.

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• Peripheral Vision (1 item): Evaluates the functional capacity of the peripheral visual field, determining the respondent’s ability to detect lateral movements, environmental objects, and approaching individuals while ambulating.

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Theoretical Framework

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The theoretical architecture of the NEI VFQ-25 is grounded in contemporary biosocial and health outcome models, most notably the Wilson and Cleary Model of Patient Outcomes (1995) and the World Health Organization’s International Classification of Functioning, Disability and Health (ICF). These models conceptualize health not merely as the absence of biological disease, but as a dynamic continuum spanning physiological status, symptom status, functional status, general health perceptions, and overall quality of life.

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The Wilson and Cleary Pathway Applied to Vision

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Within the Wilson and Cleary paradigm, ocular pathology begins at the level of biological and physiological variables (e.g., intraocular pressure elevation causing retinal ganglion cell apoptosis, or glycosylation of crystalline lens proteins). These physiological deviations manifest as symptom status (e.g., photophobia, glare, reduced spatial contrast sensitivity, or ocular pain). The NEI VFQ-25 directly bridges symptom status to functional status, which evaluates the person’s performance in physical, social, and role functions (e.g., navigating steps, reading text, driving). Functional deficits subsequently alter general health perceptions, ultimately precipitating shifts in overall quality of life through emotional decompensation, loss of personal autonomy, and heightened dependency.

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The ICF Framework: Impairment, Activity Limitation, and Participation Restriction

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Under the WHO ICF model, visual conditions are parsed into three interrelated strata:

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• Body Functions and Structures (Impairment): Structural lesions of the optic nerve, retina, or cornea that manifest as loss of visual acuity, scotomas, or contrast sensitivity losses.

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• Activity Limitations: Difficulties an individual encounters in executing specific discrete tasks (operationalized within the NEI VFQ-25 Near Activities, Distance Activities, and Driving subscales).

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• Participation Restrictions: Problems an individual encounters when attempting involvement in real-world life situations (operationalized within the Social Functioning, Role Difficulties, and Dependency subscales).

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The instrument incorporates psychological stress and coping paradigms, notably Richard Lazarus and Susan Folkman’s Transactional Model of Stress and Coping. Visual decline acts as a chronic environmental stressor. When an individual appraises their visual compromise as exceeding their coping resources, catastrophic appraisals concerning total blindness, loss of agency, and frustration emerge. By incorporating subscales dedicated to Mental Health and Dependency, the NEI VFQ-25 operationalizes this psychosocial coping breakdown.

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Validity

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The psychometric validity of the NEI VFQ-25 has been demonstrated through classical test theory (CTT) and modern item response theory (IRT) methodologies across diverse clinical cohorts and linguistic adaptations.

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Construct and Convergent Validity

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Multi-trait scaling analyses routinely substantiate the construct validity of the NEI VFQ-25. In the original multi-center development study (Mangione et al., 2001) and subsequent cross-cultural validations (e.g., the Serbian cohort by Kovač et al., 2015), item-convergent validity was confirmed by demonstrating that correlations between individual items and their hypothesized subscale exceeded the standard psychometric threshold of $r ge 0.40$ (often reaching $0.65$ to $0.88$). Item-discriminant validity was supported when correlations between items and their hypothesized subscale were significantly higher than their correlations with competing subscales (scaling success rates frequently surpassing 90%).

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Convergent validity has been established by co-administering the NEI VFQ-25 alongside generic health status instruments, predominantly the SF-36. Statistically significant, moderate-to-strong correlations are systematically observed between conceptually congruent domains:

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• NEI VFQ-25 Mental Health correlates strongly with the SF-36 Mental Health domain ($r = 0.52$ to $0.70$, $p < 0.001$).

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• NEI VFQ-25 Role Difficulties aligns with the SF-36 Role-Emotional and Role-Physical domains ($r = 0.45$ to $0.62$, $p < 0.001$).

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• NEI VFQ-25 General Health displays high correlation with the SF-36 General Health scale ($r = 0.60$ to $0.73$, $p < 0.001$).

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Clinical and Criterion-Related Validity

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The instrument exhibits robust clinical criterion validity, discriminating between healthy control populations and clinical patients across diverse stages of ocular pathology. Significant step-wise decrements in subscale and composite scores correspond with progressive clinical severity as indexed by:

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• Visual Acuity Stratification: Best-corrected visual acuity (BCVA) in the better-seeing eye demonstrates robust monotonic correlations with Near Activities ($r = -0.45$ to $-0.68$), Distance Activities ($r = -0.42$ to $-0.65$), and Composite Score ($r = -0.48$ to $-0.71$). Patients with visual acuity worse than 20/200 exhibit dramatic, statistically significant score depressions relative to patients with mild impairment (20/25 to 20/40).

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• Visual Field Loss: In glaucoma and neurological cohorts, Humphrey automated perimetry mean deviation (MD) correlates meaningfully with the Peripheral Vision subscale ($r = 0.40$ to $0.58$), Distance Activities ($r = 0.35$ to $0.50$), and Driving capability.

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• Pathology Grading: The instrument tracks anatomical gradings, demonstrating sensitivity across the Lens Opacities Classification System III (LOCS III) for cataracts and the modified Airlie House classification of diabetic retinopathy.

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Reliability

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The reliability of the NEI VFQ-25 has been systematically established across international psychometric investigations using internal consistency metrics and temporal stability analyses.

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Internal Consistency

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Internal consistency, quantified via Cronbach’s alpha, exhibits values exceeding the conventional threshold of $0.70$ for group comparisons across the vast majority of multi-item subscales:

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• Near Activities: $\alpha = 0.78$ to $0.89$ across standard international validation cohorts.

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• Distance Activities: $\alpha = 0.75$ to $0.87$.

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• Mental Health: $\alpha = 0.81$ to $0.91$, reflecting cohesive measurement of visual psychological distress.

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• Dependency: $\alpha = 0.76$ to $0.88$.

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• Role Difficulties: $\alpha = 0.74$ to $0.85$.

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• Social Functioning: $\alpha = 0.68$ to $0.79$.

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• Ocular Pain: Exhibits marginally lower alpha coefficients ($\alpha = 0.65$ to $0.74$), which psychometricians attribute to its two-item composition evaluating distinct facets: symptom frequency versus functional disruption.

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• Overall Composite Scale: Reliability estimates routinely exceed $\alpha = 0.90$ to $0.95$, denoting exceptional precision for aggregate outcome measurement.

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Test-Retest Stability

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Test-retest reliability has been verified by re-administering the questionnaire to clinically stable patients across intervals ranging from two weeks to one month. Utilizing Intraclass Correlation Coefficients (ICCs) under two-way mixed-effects models, temporal stability coefficients consistently range from $0.73$ to $0.94$ across subscales. For instance, in the Serbian adaptation (Kovač et al., 2015), stable ophthalmic outpatients reassessed over a 14-day interval demonstrated subscale ICCs ranging between $0.78$ and $0.93$, with the overall composite ICC exceeding $0.91$, verifying minimal measurement error and substantial resilience against transient environmental or mood-related fluctuations.

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Factor Analysis

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Structural evaluations of the NEI VFQ-25 have involved both classical exploratory/confirmatory factor analyses and modern Item Response Theory (specifically Rasch analysis).

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Classical Factor Analysis (EFA and CFA)

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Exploratory factor analyses utilizing maximum-likelihood extraction and varimax or oblimin rotations typically demonstrate that the 25 items load onto multi-factorial solutions mirroring the conceptualized subscales. However, significant cross-loadings frequently occur between Near Activities, Distance Activities, and Role Difficulties, as functional tasks share common underlying demands on spatial resolution and contrast perception.

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A persistent challenge in structural equation modeling (SEM) and confirmatory factor analysis (CFA) is the Driving subscale. In many elderly or severely visually impaired cohorts, rates of missing data for the Driving items range from 40% to upwards of 73% (e.g., 73.3% non-drivers in the Serbian clinical cohort), as participants have either permanently discontinued driving due to vision loss or never driven due to sociodemographic factors. Consequently, structural analysts frequently remove the Driving subscale when evaluating global covariance matrices, yielding higher-order models that demonstrate adequate fit indices (Root Mean Square Error of Approximation [RMSEA] < 0.08, Comparative Fit Index [CFI] > 0.90).

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Rasch Analysis and Modern Psychometric Critique

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Modern psychometric literature (notably Pesudovs et al., 2010; Marella et al., 2010) has applied the Andrich rating scale model to scrutinize the NEI VFQ-25. These analyses revealed critical psychometric observations:

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• Disordered Thresholds: The original response categories (e.g., matching a 5-point or 6-point polytomous response scale across difficulty and frequency items) frequently show threshold disordering, indicating that respondents struggle to reliably distinguish between adjacent categories such as ‘a little difficulty’ versus ‘some difficulty’. Collapsing adjacent categories frequently optimizes measurement precision.

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• Multidimensionality of the Composite: Rasch principal component analysis of residuals often reveals that the NEI VFQ-25 does not measure a single unidimensional latent trait. Instead, it naturally breaks down into two distinct, robust constructs: a Visual Functioning component (encompassing Near, Distance, and Peripheral vision items) and a Socioemotional / Psychosocial component (encompassing Mental Health, Dependency, and Role Difficulties).

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• Item Redundancy and Fit: Item infit and outfit mean square (MnSq) statistics generally fall within acceptable bounds (0.7 to 1.3), though items like General Health and Ocular Pain consistently show multidimensional misfit, further justifying the standard exclusion of General Health from the overall composite score.

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Instrument / Measurement Tool

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The standardized specifications for the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) are detailed below:

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• Instrument Name: National Eye Institute Visual Function Questionnaire 25-Item Version (NEI VFQ-25).

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• Test Type: Patient-Reported Outcome Measure (PROM); health-related quality of life survey.

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• Target Population: Adults (aged 18 years and older; commonly utilized in cohorts aged 40 and older) presenting with chronic ophthalmic conditions, low vision, or general age-related sensory changes.

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• Item Count: 25 core items (supplemented optionally by 12 additional items across targeted subscales in clinical research settings).

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• Administration Format: Self-administered paper-and-pencil, interviewer-administered in-person, or administered via standardized telephonic interviews. In severe vision impairment, trained interviewer administration is strongly recommended to prevent missing data and comprehension error.

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• Completion Duration: Approximately 5 to 10 minutes for the interviewer-administered format; 10 to 15 minutes for self-administration.

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• Response Scales: Categorical and Likert-type response scales varying by item, including 5-point difficulty scales (‘No difficulty at all’ to ‘Stopped doing this because of your eyesight’), 5-point frequency scales (‘None of the time’ to ‘All of the time’), 5-point agreement scales (‘Definitely true’ to ‘Definitely false’), and 6-point visual rating scales.

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• Scoring and Transformation Algorithm:n
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  • Step 1: Recoding to a 0–100 Scale: Every item is recoded such that higher values consistently reflect superior functioning or absence of disability. Response choices are linearly converted to scores of 0, 25, 50, 75, and 100 (for 5-point items) or 0, 20, 40, 60, 80, 100 (for 6-point items). Items where visual impairment forced complete cessation of an activity are coded as 0.

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  • Step 2: Subscale Calculation: Items allocated to each of the 12 subscales are summed and averaged to generate independent domain scores ranging from 0 (maximal impairment / poorest HRQOL) to 100 (complete absence of impairment / optimal HRQOL). A subscale score is generated only if at least 50% of the underlying items are non-missing.

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  • Step 3: Composite Score Computation: The global NEI VFQ-25 Composite Score is computed by taking the unweighted arithmetic mean of all subscale scores, excluding the General Health subscale. If an individual does not drive, the composite score is calculated as the mean across the remaining available domain scores.

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Permissions & Fee and Test Year

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The original National Eye Institute Visual Function Questionnaire (51-item field version) was published in 1998, and the abbreviated 25-item core instrument (NEI VFQ-25) was released in 2001 through developmental sponsorship by the National Eye Institute of the United States National Institutes of Health (NIH) in collaboration with the RAND Corporation.

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Because it was developed with federal public funding, the English-language NEI VFQ-25 is situated in the public domain. There are no royalty fees, user license charges, or proprietary access restrictions associated with utilizing the standard English instrument for academic research, non-commercial clinical trials, or everyday clinical care. Researchers and healthcare systems may reproduce and administer the scale freely.

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However, users of translated or cross-culturally validated adaptations (e.g., French, Italian, Serbian, Chinese) must consult the respective translating authors or international licensing repositories (such as the Mapi Research Trust / PROQOLID database) to obtain authorized cultural adaptations, specific manual guidelines, and cross-cultural user agreements where applicable.

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References

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• Andrich, D. (1978). A rating formulation for ordered response categories. Psychometrika, 43(4), 561–573. https://doi.org/10.1007/BF02293814

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• Campbell, D. T., & Fiske, D. W. (1959). Convergent and discriminant validation by the multitrait-multimethod matrix. Psychological Bulletin, 56(2), 81–105. https://doi.org/10.1037/h0046016

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• Kovač, B., Vukosavljević, M., Djokić Kovač, J., Resan, M., Trajković, G., Janković, J., Smiljanic, M., & Grgurević, A. (2015). Validation and cross-cultural adaptation of the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) in Serbian patients. Health and Quality of Life Outcomes, 13, Article 142. https://doi.org/10.1186/s12955-015-0330-5

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• Mangione, C. M., Berry, S., Spritzer, K., Janz, N. K., Klein, R., Owsley, C., & Lee, P. P. (1998). Identifying the content area for the 51-item National Eye Institute Visual Function Questionnaire: Results from focus groups with visually impaired persons. Archives of Ophthalmology, 116(2), 227–233. https://doi.org/10.1001/archopht.116.2.227

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• Mangione, C. M., Lee, P. P., Gutierrez, P. R., Spritzer, K., Berry, S., & Hays, R. D. (2001). Development of the 25-item National Eye Institute Visual Function Questionnaire. Archives of Ophthalmology, 119(7), 1050–1058. https://doi.org/10.1001/archopht.119.7.1050

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• Mangione, C. M., Lee, P. P., Pitts, J., Gutierrez, P., Berry, S., & Hays, R. D. (1998). Psychometric properties of the National Eye Institute Visual Function Questionnaire (NEI-VFQ). Archives of Ophthalmology, 116(11), 1496–1504. https://doi.org/10.1001/archopht.116.11.1496

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• Marella, M., Pesudovs, K., Keeffe, J. E., O’Connor, P. M., Rees, G., & Lamoureux, E. L. (2010). The psychometric validity of the NEI VFQ-25 for use in a low-vision population. Investigative Ophthalmology & Visual Science, 51(6), 2878–2884. https://doi.org/10.1167/iovs.09-4494

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• Nordmann, J. P., Viala, M., Sullivan, K., Arnould, B., & Berdeaux, G. (2004). Psychometric validation of the National Eye Institute Visual Function Questionnaire – 25 (NEI VFQ-25) French version: In a population of patients treated for ocular hypertension and glaucoma. Pharmacoeconomics, 22(3), 197–206. https://doi.org/10.2165/00019053-200422030-00005

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• Pesudovs, K., Gothwal, V. K., Wright, T., & Lamoureux, E. L. (2010). Remediating serious flaws in the National Eye Institute Visual Function Questionnaire. Journal of Cataract & Refractive Surgery, 36(5), 718–732. https://doi.org/10.1016/j.jcrs.2009.11.019

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• Suzukamo, Y., Oshika, T., Yuzawa, M., Tokuda, Y., Tomidokoro, A., Oki, K., Mangione, C. M., Green, J., Celano, M., & Fukuhara, S. (2005). Psychometric properties of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25), Japanese version. Health and Quality of Life Outcomes, 3, Article 65. https://doi.org/10.1186/1477-7525-3-65

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• Wilson, I. B., & Cleary, P. D. (1995). Linking clinical variables with health-related quality of life: A conceptual model of patient outcomes. JAMA, 273(1), 59–65. https://doi.org/10.1001/jama.1995.03520250075037

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13. Items of the Scale (Questionnaire)