Computer Vision Syndrome Questionnaire – Persian Version

Abstract

The Computer Vision Syndrome Questionnaire – Persian Version (CVS-Q FA) is an empirically validated, self-administered psychometric instrument designed to assess the presence and severity of digital eye strain among Persian-speaking computer and visual display terminal (VDT) users. Developed through a cross-cultural adaptation of the original Spanish Computer Vision Syndrome Questionnaire (CVS-Q) formulated by Seguí et al. (2015), the Persian version adheres to the stringent international methodological standards established by the International Society for Pharmacoeconomics and Outcomes Research (ISPOR). The instrument comprises 16 distinct ocular, visual, and musculoskeletal items that evaluate both symptom frequency (categorized as never, occasionally, or often/always) and symptom intensity (graded as moderate or intense). Through a non-linear recoding matrix, these dual-axis parameters yield a single severity metric for each item, producing a total composite score ranging from 0 to 32 points. Psychometric evaluations among Iranian occupational and academic populations confirm a strictly unidimensional latent factor structure via robust exploratory item factor analysis and parallel analysis for categorical data. The CVS-Q FA demonstrates strong internal consistency (Cronbach’s $\alpha = 0.80$) and temporal stability over a two-week retest interval (Intraclass Correlation Coefficient $[\text{ICC}] = 0.81$; Cohen’s $kappa = 0.65$). Scale-level content validity across a 15-member expert panel achieved an index (S-CVI) of 0.92, while item-level indices (I-CVI) consistently exceeded 0.80. Receiver Operating Characteristic (ROC) curve analysis confirmed that a diagnostic cut-off score of $ge 6$ optimizes clinical classification, providing a diagnostic sensitivity of 81.1% and a specificity of 69.2%. The instrument provides a standardized assessment metric for occupational health epidemiologists, ergonomists, and clinical optometrists evaluating digital display-induced asthenopia and ocular surface morbidity.

Keywords

Computer Vision Syndrome, Digital Eye Strain, CVS-Q, Visual Ergonomics, Asthenopia, Psychometrics, Cross-Cultural Validation, Occupational Health, Ocular Surface Disease, Persian Validation

Authors

• Milad Qolami — Department of Optometry, School of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran.
• Ali Mirzajani — Department of Optometry, School of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran.
• Elena Ronda-Pérez — Public Health Research Group, University of Alicante, San Vicente del Raspeig, Alicante, Spain.
• Natalia Cantó-Sancho — Department of Optics, Pharmacology and Anatomy, University of Alicante, San Vicente del Raspeig, Alicante, Spain (Email: [email protected]).
• Mar Seguí-Crespo — Public Health Research Group, University of Alicante, San Vicente del Raspeig, Alicante, Spain.

Purpose

The primary purpose of the Computer Vision Syndrome Questionnaire – Persian Version (CVS-Q FA) is to deliver a standardized, linguistically adapted, and psychometrically validated clinical tool for detecting, monitoring, and quantifying Computer Vision Syndrome (CVS)—interchangeably termed Digital Eye Strain (DES)—among Persian-speaking populations. The rapid digitalization of work, education, and social connectivity across Iran has led to extended exposure to visual display terminals (VDTs), including personal computers, laptops, smartphones, and tablets. Prolonged interaction with near-point digital displays imposes unique biomechanical and physiological stresses on the human visual apparatus, producing complex symptom patterns that disrupt workplace performance, diminish academic productivity, and impair quality of life.

Historically, epidemiological research on digital eye strain within Persian-speaking demographics has been constrained by significant methodological heterogeneity. In the absence of an officially validated Persian measurement scale, researchers and occupational medicine clinicians relied heavily on ad-hoc, unstandardized questionnaires, non-validated translations of isolated survey questions, or rudimentary single-item self-report queries (e.g., “Do your eyes feel tired after using a computer?”). Such variable measurement strategies yielded unstable prevalence estimates in the Middle Eastern region, spanning from 40% to upwards of 90%, while preventing valid cross-study meta-analyses and international comparisons. The creation and psychometric formalization of the CVS-Q FA directly closes this empirical gap by introducing a culturally adapted assessment model supported by verified diagnostic thresholds.

In occupational health surveillance, the CVS-Q FA functions as a first-line diagnostic screening instrument capable of distinguishing between workers who experience transient, sub-clinical visual fatigue and those who meet the diagnostic criteria for clinical computer vision syndrome. Its structured scoring algorithm captures both how often symptoms appear and how severe they are when present. This dual-axis approach prevents misclassification; an individual who experiences mild symptoms daily does not receive the same clinical rating as one who suffers debilitating pain or diplopia several times a week. Furthermore, the questionnaire serves as a primary endpoint metric in interventional research, enabling visual ergonomists to evaluate the therapeutic efficacy of workplace adjustments—such as anti-reflective filters, ambient lighting modifications, monitor re-positioning, scheduled ergonomic pauses (e.g., the 20-20-20 rule), blue-light filtering lenses, and artificial tear formulations.

Psychological Construct

Computer Vision Syndrome is operationalized psychometrically as a unidimensional, latent construct encompassing a spectrum of ocular, visual, and non-ocular physiological complaints triggered by the prolonged engagement of the accommodative, vergence, and ocular surface mechanisms during digital display operation. Although the clinical presentation of CVS includes several distinct physiological pathways, psychometric modeling confirms that these varied symptoms load onto a single underlying continuum of strain severity.

The construct encompasses three primary physiological domains:

• Ocular Surface and External Mechanisms: Symptoms in this domain stem directly from disrupted tear film dynamics and blink mechanics. Staring at luminous, pixelated screens significantly decreases spontaneous blink rates—often by more than 50%—while increasing the proportion of incomplete blinks. This causes rapid evaporation of the pre-corneal tear film, localized hyperosmolarity, friction-induced microtrauma to the corneal and conjunctival epithelium, and subsequent ocular surface inflammation. Within the CVS-Q FA, this mechanism is captured through items evaluating Burning (سوزش چشم), Itching (خارش چشم), Foreign Body Sensation (احساس وجود جسم خارجی در چشم), Tearing (اشک‌ریزش), Excessive Blinking (پلک زدن بیش از حد), Eye Redness (قرمزی چشم), and Dryness (خشکی چشم).
• Internal and Accommodative-Vergence Mechanisms (Asthenopia): Maintaining continuous visual focus at fixed, near-to-intermediate working distances requires sustained contraction of the intraocular ciliary muscle for accommodation, alongside continuous tonic activation of the extraocular medial rectus muscles to preserve convergence. Over extended periods, this prolonged muscular demand leads to muscle fatigue, transient ciliary spasms, accommodative micro-fluctuations, and vergence adaptation failure. The CVS-Q FA measures this internal strain through items such as Eye Pain (درد چشم), Blurred Vision (تاری دید), Double Vision (دوبینی), and Difficulty Focusing for Near Vision (مشکل در تمرکز/تطابق برای دید نزدیک).
• Visual Processing and Extraocular Symptoms: Beyond direct ocular mechanisms, the construct accounts for neurological and environmental strain factors, such as luminance contrast disparities, digital screen glare, display flicker, high-energy short-wavelength visible light (blue light) scatter, and poor upper-body ergonomic posturing. These conditions generate symptoms including Heavy Eyelids (سنگینی پلک‌ها), Increased Sensitivity to Light (افزایش حساسیت به نور / فوتوفوبیا), Colored Halos Around Objects (دیدن هاله‌های رنگی در اطراف اجسام), Feeling That Sight Is Worsening (احساس بدتر شدن یا ضعیف شدن دید), and secondary tension-type Headache (سردرد).

The psychometric integrity of this construct relies on measuring symptom frequency alongside perceived intensity. Physiological discomfort that is frequent yet mild may affect daily visual processing differently than infrequent, severe episodes. By mapping these dimensions onto a single severity index, the CVS-Q FA reliably orders respondents along a continuous latent trait ($ heta$) of digital eye strain severity.

Theoretical Framework

The theoretical framework of the CVS-Q FA integrates visual ergonomic theory, ocular biomechanics, and contemporary psychometric measurement principles. At its conceptual foundation is the Ocular Surface and Biomechanical Load Model of Digital Display Interaction, which explains how screen-based near work differs qualitatively from reading printed text.

Printed text presents stable, reflected characters with sharp, distinct margins. In contrast, cathode-ray tube (CRT), liquid-crystal display (LCD), and organic light-emitting diode (OLED) screens generate illuminated characters made of pixels that are brightest at the center and diminish in luminance toward their perimeters. Consequently, the human eye struggles to maintain a stable accommodative resting point on electronic displays. The visual system repeatedly relaxes toward the dark focus point (or tonic accommodation point) and must continuously re-engage the ciliary muscle to regain sharp focus on screen elements. This constant accommodative hunting places substantial physiological stress on the neuromuscular control of the ciliary body.

Concurrently, the Cognitive Blink Suppression Theory explains the ocular surface breakdown central to CVS. During visually demanding, cognitively intensive screen tasks, the central nervous system down-regulates the spontaneous blink rate to maximize continuous sensory input. This leads to tear break-up times (TBUT) falling below the inter-blink interval, leaving the corneal epithelium directly exposed to ambient air and low-humidity office environments. The resulting mechanical friction and sensory nerve excitation manifest as sensations of grittiness, stinging, and reflex tearing.

From a psychometric perspective, the instrument applies Classical Test Theory (CTT) along with modern Item Factor Analysis for polytomous items. The underlying model treats the 16 manifest symptom indicators as monotonic functions of the single continuous latent variable, Computer Vision Syndrome. Because clinical symptom reporting is inherently non-linear—where the perceived impact of a symptom escalates non-linearly when both frequency and intensity are elevated—the scale uses a tailored, empirical scoring matrix. This design ensures that the composite score accurately reflects the respondent’s overall physiological burden, providing a valid diagnostic threshold for occupational screening.

Validity

The validation of the CVS-Q FA was carried out following the ten-stage cross-cultural adaptation guidelines of the ISPOR Task Force for Translation and Cultural Adaptation. This structured methodology ensured conceptual, linguistic, semantic, and operational equivalence between the source Spanish questionnaire and the target Persian version.

Content and Face Validity

Content validity was evaluated by an expert committee comprising 15 Iranian optometrists and occupational health specialists. The panel examined each translated item for relevance, clarity, and conceptual fidelity using standardized rating protocols. The overall Scale-Level Content Validity Index (S-CVI) reached 0.92, well exceeding the recognized 0.80 benchmark for psychometric adequacy. Individual Item-Level Content Validity Indices (I-CVI) all exceeded 0.80 following minor linguistic refinements, confirming that the 16 symptoms fully cover the clinical presentation of CVS in the target linguistic and cultural setting.

Face validity and comprehensibility were subsequently tested through cognitive debriefing interviews with target end-users, including university administrative employees and postgraduate research students. Participants confirmed that the item instructions, recall period, and dual-axis response scales were intuitive and clear, requiring an average completion time of under three minutes.

Criterion and Diagnostic Validity

Criterion validity was evaluated against clinical diagnosis through comprehensive optometric examinations, which served as the diagnostic reference standard. These clinical assessments included tear film stability measurements (tear break-up time), ocular surface integrity evaluations via slit-lamp biomicroscopy, and accommodation and binocular vergence testing. Receiver Operating Characteristic (ROC) curve analysis was used to calculate the diagnostic accuracy of the questionnaire across various scoring cut-offs.

The Area Under the Curve (AUC) demonstrated strong diagnostic discrimination. At the pre-established cut-off score of $ge 6$ points, the CVS-Q FA demonstrated:

• Diagnostic Sensitivity: 81.1% (95% CI: 71.7% – 88.4%)
• Diagnostic Specificity: 69.2% (95% CI: 58.0% – 78.7%)

This balance between sensitivity and specificity confirms that the questionnaire effectively identifies individuals with clinical digital eye strain (limiting false negatives in occupational screening) while maintaining acceptable specificity to avoid misclassifying healthy screen users.

Reliability

The reliability of the CVS-Q FA has been confirmed through evaluations of internal consistency and temporal test-retest stability across multiple independent cohorts.

Internal Consistency

Internal consistency was examined using Cronbach’s alpha coefficient based on polychoric correlation estimations suited for categorical and ordinal response formats. The 16 items produced an overall Cronbach’s alpha of 0.80. This value sits within the psychometric target range (0.75–0.90), demonstrating that the items reliably measure the same underlying construct without excessive redundancy or narrow item overlap. Corrected item-total correlation values for all 16 symptoms exceeded the 0.30 threshold, showing that each individual item contributes meaningfully to the overall score.

Test-Retest Reliability and Reproducibility

Temporal stability was evaluated in a dedicated subsample of 46 computer users who completed the CVS-Q FA on two separate occasions spaced 10 to 14 days apart under stable environmental and workplace conditions. The analysis confirmed the temporal stability of the scale:

• Intraclass Correlation Coefficient (ICC): The two-way mixed-effects, absolute-agreement ICC for the total continuous score was 0.81 (95% CI: 0.69 – 0.89), demonstrating good-to-excellent test-retest reliability over time.
• Cohen’s Kappa ($kappa$): When participants were classified into categorical diagnostic groups (CVS positive vs. CVS negative using the $ge 6$ threshold), stability analysis yielded a Cohen’s kappa of 0.65 (95% CI: 0.43 – 0.87), indicating substantial diagnostic agreement between test sessions.

These findings show that the CVS-Q FA reliably measures sustained symptom severity while remaining largely unaffected by short-term, random day-to-day fluctuations in visual demands.

Factor Analysis

The structural validity of the CVS-Q FA was analyzed using item factor analysis specifically configured for ordered categorical variables, as Pearson correlation matrices can distort underlying factor structures when applied to skewed ordinal responses.

Assessment of Multivariate Distribution

Item distribution evaluations showed significant departures from multivariate normality (Mardia’s coefficient for multivariate skewness and kurtosis: $p < 0.001$). Consequently, factor extraction was conducted using a polychoric correlation matrix combined with robust diagonally weighted least squares (DWLS) and unweighted least squares (ULS) estimation methods.

Dimensionality and Fit Indices

To determine the scale’s dimensionality, the researchers ran a parallel analysis based on minimum rank factor analysis across 500 random permutations of the empirical dataset. The empirical first eigenvalue accounted for the majority of the common variance, whereas the second empirical eigenvalue fell below the 95th percentile of the simulated random datasets. This result confirmed that the scale has a unidimensional structure.

Confirmatory modeling of this single-factor solution demonstrated solid goodness-of-fit indices:

• Comparative Fit Index (CFI): > 0.95
• Tucker-Lewis Index (TLI): > 0.95
• Root Mean Square Error of Approximation (RMSEA): < 0.06 (90% CI: 0.02 – 0.08)

All 16 standardized factor loadings were statistically significant ($p < 0.001$), ranging from 0.42 to 0.79. Because all items loaded cleanly onto a single latent factor without meaningful residual correlation clusters, the structural analysis justifies calculating a single composite score rather than dividing the tool into separate subscales.

Instrument / Measurement Tool

• Instrument Name: Computer Vision Syndrome Questionnaire – Persian Version (CVS-Q FA)
• Original Authors: Mar Seguí-Crespo, Jesús Cabrero-García, Antonio Crespo, José Verdú, and Elena Ronda-Pérez (2015)
• Persian Adaptation Authors: Milad Qolami, Ali Mirzajani, Elena Ronda-Pérez, Natalia Cantó-Sancho, and Mar Seguí-Crespo (2022)
• Instrument Type: Standardized self-report symptom inventory / patient-reported outcome measure (PROM)
• Target Population: Adult computer users, visual display terminal (VDT) operators, office workers, telecommuters, and university students
• Administration Format: Self-administered paper-and-pencil questionnaire or secure digital/online survey
• Completion Time: Approximately 2 to 4 minutes
• Item Count: 16 symptom items
• Item Assessment Framework: Each symptom is rated across two distinct axes:
  • Frequency ($F$): Rated as Never (does not occur at all), Occasionally (sporadic occurrence or once a week), or Often/Always (at least 2 or 3 times a week).
  • Intensity ($I$): Evaluated only if the symptom occurs; rated as Moderate or Intense.
• Item Scoring Conversion Rules:
  • If Frequency = 0 (Never), Item Score = 0 (Intensity is recorded as not applicable/0).
  • If Frequency = 1 (Occasionally) and Intensity = 1 (Moderate), Item Score = 1.
  • If Frequency = 1 (Occasionally) and Intensity = 2 (Intense), Item Score = 1.5.
  • If Frequency = 2 (Often/Always) and Intensity = 1 (Moderate), Item Score = 1.5.
  • If Frequency = 2 (Often/Always) and Intensity = 2 (Intense), Item Score = 2.
• Total Score Calculation: The sum of all 16 recoded item scores yields a total composite score ranging from 0 to 32 points.
• Diagnostic Cut-off & Interpretation:
  • Total Score < 6: Absence of Computer Vision Syndrome (sub-clinical/asymptomatic).
  • Total Score $ge$ 6: Indicates the presence of Computer Vision Syndrome (diagnostic sensitivity: 81.1%; specificity: 69.2%).

Permissions & Fee and Test Year

The original Computer Vision Syndrome Questionnaire (CVS-Q©) was copyrighted by the University of Alicante in 2015. The Persian adaptation (CVS-Q FA) was formally validated and published in 2022 by Milad Qolami and colleagues in the journal International Ophthalmology. The questionnaire is available for academic, non-commercial research, and institutional occupational health screenings. Clinicians and researchers interested in utilizing the Persian version are encouraged to contact the primary developers at the University of Alicante (Public Health Research Group, Department of Optics, Pharmacology and Anatomy, contact: [email protected]) or the corresponding adaptation authors to obtain the validated clinical assessment forms.

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13. Items of the Scale (Questionnaire)