Sunglasses with thick temples and frame constrict temporal visual field.

PURPOSE: Our aim was to compare the impact of two types of sunglasses on visual field and glare: one ("thick sunglasses") with a thick plastic frame and wide temples and one ("thin sunglasses") with a thin metal frame and thin temples. METHODS: Using the Goldmann perimeter, visual field surface areas (cm²) were calculated as projections on a 30-cm virtual cupola. A V4 test object was used, from seen to unseen, in 15 healthy volunteers in the primary position of gaze ("base visual field"), then allowing eye motion ("eye motion visual field") without glasses, then with "thin sunglasses," followed by "thick sunglasses." Visual field surface area differences greater than the 14% reproducibility error of the method and having a p < 0.05 were considered significant. A glare test was done using a surgical lighting system pointed at the eye(s) at different incidence angles. RESULTS: No significant "base visual field" or "eye motion visual field" surface area variations were noted when comparing tests done without glasses and with the "thin sunglasses." In contrast, a 22% "eye motion visual field" surface area decrease (p < 0.001) was noted when comparing tests done without glasses and with "thick sunglasses." This decrease was most severe in the temporal quadrant (-33%; p < 0.001). All subjects reported less lateral glare with the "thick sunglasses" than with the "thin sunglasses" (p < 0.001). CONCLUSIONS: The better protection from lateral glare offered by "thick sunglasses" is offset by the much poorer ability to use lateral space exploration; this results in a loss of most, if not all, of the additional visual field gained through eye motion.

Eye motion increases temporal visual field extent.

PURPOSE: To study the impact of eye motion on visual field extent. METHODS: Visual fields were tested in 15 healthy volunteers with the Goldmann perimeter using a V4 test object, from seen to unseen, first in primary position of gaze, then allowing eye motion. Temporal points falling out of the cupola were tested again after a controlled nasal head rotation using a headband prototype fitted with a line-laser level having two orthogonal vial levels. Visual field surface areas (cm(2) ) were calculated as projections on a 30-cm virtual Goldmann cupola, whose extent would have been large enough to include all points. Reproducibility error of the method assessed by calculation of the relative difference between surface areas of 12 visual field tests and 12 visual field retests was estimated at 14%. Hertel exophthalmometry was recorded to study the influence of globe position on visual field extent. RESULTS: Binocular visual field surface area increased by 37% with eye motion (p-value=1.20·10(-9) ). This increase was highest (46%; p-value=1.2·10(-24) ) in the temporal quadrant. Median maximal visual field temporal eccentricity with eye motion was 128.3° (minimum: 109.5°; maximum: 137.7°) and more than 135° in four eyes of three subjects. Hertel exophthalmometry was positively linked to visual field temporal surface area with eye motion (p-value=0.013). CONCLUSIONS: Eye motion greatly expands the temporal visual field. This peculiarity is likely an adaptation to terrestrial life with upright bipedal locomotion and may save head movements through horizontal eyeball scanning.