The influence of visual field defects and other clinical parameters on reading performance: A retrospective study in a low vision population

Purpose: To examine the influence of visual field defects and other parameters, such as age, diagnosis, visual acuity, and magnification need, on reading performance in a low vision population. Methods: A total of 223 low vision patients were fitted with the best visual aid for reading according to their magnification need. Reading performance was related to distance visual acuity, magnification need, diagnosis, and visual field status. The results of kinetic Tuebingen manual perimetry were categorized according to the location, size, shape, and density of the scotoma. The fixation locus during perimetry was determined by the location of the blind spot. The outcome variable was reading performance of newspaper print according to the following categories: 1, fluent; 2, struggling; and 3, no reading ability. Results: A total of 71% of the patients were fluent, 25% were struggling, and 4% were non-readers. The affiliation to a reading category was related to visual acuity, magnification need, and diagnosis, but not to age and type of field defect alone. In patients with absolute central scotoma, it was related to fixation stability, but not to fixation locus alone. In absolute central scotoma, stable and eccentric fixation were favorable. Conclusions: The categorization of visual field defects, which considers the two main visual preconditions for reading (resolution and size of the reading visual field), helps to understand reading difficulties and improves the judgement for rehabilitation in the individual patient. An integrative view of visual acuity, magnification need, and visual field status allows the determination of the preconditions necessary to improve the individual patient's reading performance.