Development of the Glaucoma Visual Functioning Questionnaire-40 and Its Psychometric Properties

Glaucoma is the leading cause of irreversible blindness in the world. It is estimated that by 2040, the number of glaucoma patients in the world's population aged 40-80 will exceed 110 million [1]. As a chronic progressive blindness disease, glaucoma can seriously damage visual function such as visual acuity, visual field and contrast sensitivity, restrict patients' daily life activities and leads to a serious decline in vision-related quality of life (VRQOL) and health-related quality of life (HRQOL) [2-5]. Comprehensive evaluation of the visual function of glaucoma patients can not only educate the impact of glaucoma, but also reflect the effect of clinical treatment or rehabilitation interventions. However, the objective testing methods commonly used in clinic, such as visual acuity, visual field and contrast sensitivity, can only be used to evaluate part of the visual function of patients, which can not reflect the impact of disease and corresponding interventions from the point of view of patients. The use of patient defined measures of vision function in ophthalmic assessment and treatment evaluation is now well accepted and a number of questionnaires have been developed, such as NEI VFQ-25, LVQOL and SF-36, which mostly focus on investigating VRQOL or HRQOL[6-10]. There are comparatively few vision function questionnaires developed to measure the visual ability for glaucoma patients. The objective of this study is to develop and test the psychometric properties of a self-report questionaire, the Glaucoma Visual Functioning Questionnaire-40 (GVFQ-40), which was designed to measure the difficulty of daily activities of glaucoma patients and evaluate the effectiveness of clinical treatment or rehabilitation interventions.

The GVFQ-40 consists of 40 items and measures the impact of glaucoma on restriction of participation in daily activities in five domains of functioning (mobility, visual tracking, reading, identification and night vision ). Each item has six answer options, that is, no difficulty (score = 1), mild difficulty (score = 2), moderate difficulty (score = 3), extremely difficult (score = 4), completely unable to complete (score = 5), and do not performed for nonvisual reasons (no score).