An Empirical Study of the AGIS Visual Field Metric and Its Seasonal Variations

The severity of the glaucoma eye disease is usually measured by the Advanced Glaucoma Intervention Studies (AGIS) metric. The metric provides a value between zero and twenty inclusive, where the former represents no evidence of glaucoma and the latter the most advanced of measurements. In a previous study by Montolio et al., the season in which the test was undertaken was shown to affect the value of eye measurements; the lowest sensitivity was found in Summer and the highest sensitivity found in Winter and Spring. In this paper, we partially replicate that study with a different set of data from 2468 patients obtained from Moorfields Eye Hospital, London. We decomposed the data according to the four seasonal dates to determine if extra sensitivity meant that patients' results improved in Winter.