It is commonly believed that variability increases with eccentricity. Very few studies, however, quantified the effect of test location on the relationship between variability and sensitivity. Almost 35 years ago, Flammer et al.
42 examined patients with glaucoma, glaucoma suspects, and healthy subjects, and found that fluctuation was not related to the test location in the glaucoma suspects and healthy subjects, but was slightly increased in glaucoma patients in the upper hemifield, which is the most frequently affected area. Werner et al.
28 evaluated 67 glaucoma patients, and found that fluctuation increased with eccentricity, but the effect of test location disappeared with the correction for differences in sensitivity. These results were replicated by Boeglin and colleagues
29 in 93 clinically stable eyes of 67 glaucoma patients. In a group of healthy subjects, Heijl et al.
12 found contradictory results with increased fluctuation in the peripheral locations. In a subsequent study, Heijl and colleagues
33 evaluated a small cohort of glaucoma patients with a test–retest strategy, and found that an increase of variability with eccentricity is seen in patients with mild-to-moderate damage, but the difference was no longer detected for locations with worse glaucomatous damage, defined as total deviation values worse than −10 dB. In a recent study, Gardiner
5 tested the impact of eccentricity on variability through linear regression of large-scale longitudinal data and found an increased variability at the peripheral test locations only for sensitivity values above 28 dB. Surprisingly, we observed an increase of fluctuation related to eccentricity, as the variability was higher within 10° from fixation compared with more than 20°. Although these results are similar with those by Gardiner,
5 the explanation of these results is not straightforward. Differences in study design, sample size, test strategy, and degrees of VF test can justify discrepancies in the study by Heijl et al.
12 According to the hill of vision, central locations have normally higher threshold sensitivity values compared with peripheral locations, and the same sensitivity value may represent a more significant level of damage in the central area because sensitivity at central locations is normally higher than at peripheral locations. The results did not change when we repeated the analysis on the total deviation map, which accounts for deviation from normal age-matched values for each test location.