Accommodation and visual discomfort: a laboratory, optometric and subjective analysis

Near-vision activities can induce visual discomfort, accompanied by symptoms that suggest accommodative dysfunction. However, results reported in the current literature are inconsistent regarding the link between visual discomfort and accommodation. This study aimed to analyse the accommodative response before and after various visual tasks designed to induce visual discomfort. Twelve volunteers (26 ± 3years) participated. Five visual tasks, varying in duration, viewing distance, and the congruence between accommodation and vergence, were performed in random order. Objective static and dynamic metrics of accommodation were systematically recorded before and after each task at far (0.20 D) and near (2.50D) distances. Optometric tests of accommodation and subjective assessments of visual discomfort were also performed. Among the five visual tasks, the two-hour task at 3.00 D accommodative demand (NV33) produced the greatest changes in subjective (visual discomfort) and objective (accommodation) measures. Following the NV33 task, variability of accommodation and the time constant of the accommodative response increased significantly (mean ± SE: +0.03 ± 0.01 D and + 140 ± 66 ms, respectively), while peak velocity of accommodation decreased significantly (-1.51 ± 0.63 D/s). Subjective visual discomfort also showed significant and systematic increases, while optometric tests results remained unchanged across all tasks. The variations in variability of accommodation, time constant and peak velocity may be associated with visual discomfort, although their clinical relevance remains unclear. Nevertheless, the NV33 task appears to be a useful experimental condition for studying visual discomfort.