Validation and Update of the Glaucoma Quality of Life (GQL)-15 Questionnaire for Spanish-Speaking Individuals

Abstract

Background and objective: Glaucoma, a leading cause of preventable blindness, significantly impacts patients' quality of life (QoL). The GQL-15 (1999) assesses functional disability due to glaucoma through 15 items across 4 domains. However, it has not been validated in Spanish. This study aimed to validate and update the GQL-15 for Spanish-speaking individuals.

Methods: We conducted a cross-sectional study with individuals diagnosed with glaucoma at 2 ophthalmological referral centers in Cali-Colombia. Researchers translated the GQL-15 into Spanish and modified it by replacing the 'reading newspaper' item with 'reading on a cellphone/mobile/smartphone' to modernize the questionnaire (GQL-15 m). The GQL-15 m was tested for validity and reliability using Cronbach's alpha (α) coefficient, exploratory factor analysis, and criterion validity. Reproducibility was assessed through a 2-week test-retest analysis.

Results: A total of 157 out of 468 eligible patients with glaucoma participated in the survey (33% response rate). The mean age was 67 ± 12 years (64%, women). The GQL-15 m showed a mean total score of 29.3 ± 7.31, suggesting good QoL. Internal consistency was high for both the GQL-15 (α = 0.97) and GQL-15 m (α = 0.96). Criterion validity was supported by significant correlations between the GQL-15 m scores and the National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ 25), World Health Organization Quality of Life-BREF (WHOQoL-BREF), Glaucoma Symptom Scale (GSS), Glaucoma Utility Index (GUI), and visual acuity. Reproducibility was high, with an intraclass correlation coefficient (ICC) of 0.89.

Conclusions: The GQL-15 m is a reliable and valid instrument for assessing QoL in Spanish-speaking individuals with glaucoma and has potential for broader application across various cultural contexts.

Keywords: Adaptación cultural; Calidad de vida; Cultural adaptation; Glaucoma; Quality of life; Traducción; Translation; Validación; Validation.