Introduction
Glaucoma progressively impairs visual fields and functional vision, which directly affects daily activities, mobility, and independence. However, objective clinical measures such as intraocular pressure or visual field indices do not fully capture how patients experience their disease. Vision-specific quality-of-life tools are essential to bridge this gap. Specifically, Patricia Nelson and colleagues developed the Glaucoma Quality of Life-15 (GQL-15) and introduced it in the Journal of Glaucoma in 2003. Since then, the tool has earned more than 1,000 citations. Consequently, it is now one of the most widely used instruments for assessing vision-related quality of life.
This article provides a structured overview of the GQL-15, including its scoring, reliability, and research value.
Key Features of the Glaucoma Quality of Life-15 (GQL-15)
Purpose and Use
The GQL-15 measures how glaucoma-related visual field loss affects a patient’s ability to perform everyday tasks. Unlike clinical measures, the GQL-15 captures the patient’s functional experience in real-life situations.
In addition, the tool offers flexibility in scoring. The original 2003 summative scoring is simple and works well for routine clinical use. Alternatively, the 2011 Rasch-based scoring provides superior precision for research and clinical trials. Because it focuses on task difficulty, the GQL-15 gives clinicians a practical way to measure independence and safety.
Target Population
The GQL-15 is validated for adults aged 18 years and older. This includes:
Young adults (18–24 years)Middle-aged adults (25–44 years)Older adults (45–64 years)Seniors (65+ years)While any adult with glaucoma can use the GQL-15, most validation studies have focused on middle-aged and older populations.
Structure
The questionnaire contains 15 items covering four factors of visual disability:
Central and near vision (2 items)Peripheral vision (6 items)Dark adaptation and glare (6 items)Outdoor mobility (1 item)Items ask patients how difficult common visual tasks are, such as reading small print, avoiding obstacles, seeing in dim light, and moving outdoors.
Scoring Method
Each item is rated on a 5-point difficulty scale: 1 = No difficulty → 5 = Severe difficulty,
0 = Task not performed for non-visual reasons (treated as missing).
1) Traditional Summative Scoring (2003): Total score = sum of 15 items, Range: 15 to 75, Higher scores = poorer quality of life, Zeros treated as missing; mean substitution recommended. Handling Zeros: If a participant selects '0' (N/A), do NOT treat it as zero in the sum. Instead, treat it as a missing value and calculate the mean score of the answered items to maintain accuracy.
2) Rasch-Based Scoring (2011 Reengineering): Raw scores converted to a logit interval scale, rescaled to 0–100 (0 = no difficulty, 100 = extreme difficulty), provide superior psychometric precision for research. A response of 0 (activity not performed for non-visual reasons) is typically treated as missing for scoring purposes and excluded from the calculation of total/subscale scores.
Administration Format
The GQL-15 requires 5–10 minutes to complete.
It can be administered via:
Paper formsDigital platformsIn-person interviewsPhone/video interviewsNo training is required.
Applications of the GQL-15
The GQL-15 supports:
Monitoring: It tracks changes in difficulty performing daily visual tasks. Because the questionnaire focuses on task difficulty, it provides measurable data on how visual field loss affects daily life across follow-up visits.Treatment planning: It assists in evaluating baseline functional impairment before initiating or adjusting therapy. It provides outcome data after medical, laser, or surgical interventions.Research: The GQL-15 is used in structured study designs to evaluate the relationship between visual field loss and quality of life and the functional burden of glaucoma in different populations.For example, the instrument focuses on task difficulty, and it provides structured data on how glaucoma affects everyday functioning. Thus, it supports comprehensive assessment when evaluating disease burden and treatment effectiveness.
Languages and availability
Validated versions include:
Arabic (Moroccan)EnglishMandarin ChineseSpanishRussianGermanMoreover, Serbian, Turkish, Persian, Hindi, and Portuguese are also available. Permission from the publisher is typically required for reproduction or translation.
Reliability and Validity
The GQL-15 is highly reliable and valid in the original study: Internal consistency (Cronbach’s alpha): 0.95; test–retest reliability: r = 0.87.
These findings indicate that the questionnaire provides stable and consistent results when administered repeatedly under similar conditions. The GQL-15 is supported by multiple validation studies, including:
Original study: LinkAssessing quality of life in patients with glaucoma using the Glaucoma Quality of Life-15 (GQL-15) questionnaire, Goldberg et al. (2009): Linkvalidation of the Chinese version: Linkvalidation of the Moroccan version: LinkLimitations and Considerations
Despite its strengths, the GQL-15 has several limitations:
Self-report measure: The questionnaire depends entirely on patient perception. Therefore, responses may vary based on mood, expectations, or personal interpretation rather than objective visual performance.Social desirability bias: scores may underestimate the true level of functional limitation, particularly in older adults who wish to avoid stigma related to visual disability.Other Versions And Related Questionnaires
Several complementary tools may be used alongside the GQL-15.
Rasch-optimized 9-item short form: GAL-9 (Glaucoma Activity Limitation): Researchers applied Rasch analysis to improve measurement precision and psychometric performance. As a result, raw ordinal scores were transformed into interval-level logit scores. It is now considered the most psychometrically robust method for interpreting GQL-15 results in clinical trials.Glaucoma Symptom Scale (GSS): Measures ocular symptoms such as burning, tearing, and blurred vision. Focuses on symptom burden rather than functional disability.Symptom Impact Glaucoma (SIG) scale: Assesses the perceived impact of glaucoma symptoms, emphasizing subjective experience. It is used in quality-of-life research contexts.25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25): Broader vision-related quality of life instrument. It covers multiple eye diseases, not glaucoma-specific. It includes emotional and social vision-related domains.Additional Resources
Original study: LinkRash analysis of the GQL-15: LinkAccess the GQL-15 PDFFor inquiries and more information, contact Dr. Patricia Nelson: Patricia.Nelson@scotdb.comFrequently Asked Questions (FAQ)
Who can use the GQL-15?Clinicians and researchers use it for adults with glaucoma to assess vision-related quality of life.
How long does it take to complete the GQL-15?Approximately 5–10 minutes.
How is the GQL-15 administered?Paper, digital, or interview formats.
Is there any cost to using the GQL-15?Permission from the publisher is generally required for use or reproduction. For more inquiries, please contact Dr. Patricia Nelson at her email: Patricia.Nelson@scotdb.com
A Word from ResRef
The Glaucoma Quality of Life-15 (GQL-15) is a highly recommended, essential tool for both glaucoma research and clinical practice. It is praised for being robust, concise, and well-validated.
References
Nelson, P., Aspinall, P., Papasouliotis, O., Worton, B., & O'Brien, C. (2003). Quality of life in glaucoma and its relationship with visual function. Journal of glaucoma, 12(2), 139–150. LinkGoldberg, I., Clement, C. I., Chiang, T. H., Walt, J. G., Lee, L. J., Graham, S., & Healey, P. R. (2009). Assessing quality of life in patients with glaucoma using the Glaucoma Quality of Life-15 (GQL-15) questionnaire. Journal of glaucoma, 18(1), 6–12.LinkZhou, C., Yao, J., Qian, S., & Wu, P. (2013). Linguistic and psychometric validation of the Chinese version of the Glaucoma Quality of Life-15 (GQL-15-CHI): a cross-sectional study. Health and quality of life outcomes, 11, 188. LinkMaiouak, M., El Ouazzani Taybi, H., Benmaamar, S., El Harch, I., Jho Diagne, B., Berraho, M., Abdellaoui, M., Tachfouti, N., Benatiya Andaloussi, I., & El Fakir, S. (2023). Cross-cultural adaptation and validation of the Moroccan version of the Glaucoma Quality of Life-15 (GQL-15) questionnaire in patients with glaucoma. Journal Français d’Ophtalmologie, 46(6), 581–588. LinkKhadka, J., Pesudovs, K., McAlinden, C., Vogel, M., Kernt, M., & Hirneiss, C. (2011). Reengineering the glaucoma quality of life-15 questionnaire with Rasch analysis. Investigative ophthalmology & visual science, 52(9), 6971–6977. Link