[Measurement of glaucoma-specific functionality with the GQL-15 and correlation with parameters of visual function].

Introduction: Glaucoma is one of the leading causes of irreversible blindness worldwide and can have a significant impact on patient quality of life and vision-related functioning. The Glaucoma Quality of Life 15 (GQL-15) questionnaire is a disease-specific instrument to evaluate and quantify functional impairment of patients with glaucoma. This study evaluated the German version of the GQL-15 including correlations with perimetric parameters.
Methods: A German version of the GQL-15 containing 15 items was developed and evaluated in 98 patients with glaucoma in different stages of the disease. The GQL-15 results were correlated with the perimetric parameters mean deviation (MD) and pattern standard deviation (PSD) of the better and worse eye. Classical and probabilistic test analyses (Rasch model) were performed.
Results: The mean GQL-15 value was 77.3 ± 21.7 (SD) and most items of the GQL-15 correlated significantly with the MD of the worse eye (r = -0.416; p = 0.0014) and the better eye (r = -0.304; p = 0.02). There was also a highly significant correlation between glaucoma-specific QoL and visual acuity. A short version containing nine items yielding a higher psychometric performance can also be used.
Conclusions: The German version of the GQL-15 is a potent instrument to evaluate impairment in vision-specific functioning of patients with glaucoma. The GQL-15 values are better correlated with the sensitivity of the eye with the more severe glaucomatous damage. The data can help for a better understanding of individual patient impairment to improve medical advice and therapy of patients with glaucoma.