Changes in plantar load distribution in legally blind subjects

Abstract

We investigated the impact of visual impairment on balance control. We measured the center of pressure (COP) between the two feet and plantar surface pressures on each foot in 18 normal-sighted participants and compared their data with measures from 18 legally blind participants, either acquired or congenital. Pressures were measured in open- and closed-eye conditions using a baropodometric resistive plate. In the eyes-open condition, there were no differences between the sighted and legally blind groups in COP displacement. However, participants with visual loss had significantly increased pressures in two metatarsal regions (M1 and M2 zones) of the plantar surface in both viewing conditions (p < 0.05). The differences in pressure measures between the normally sighted and legally blind groups could be attributed mainly to the subgroup of subjects with acquired impairment. Our findings suggest that subjects with visual impairment present increased metatarsal pressures (i.e. forefoot), not yet associated to anterior displacement of COP or impaired balance control.

Fig 1. Representation of the zones of the foot where plantar pressures were quantified.

Forefoot is represented by the T1 (first toe), T2-5 (2nd-5th toes), M1 (1st metacarpal), M2 (2nd metacarpal), M3 (3rd metacarpal), M4 (4th metacarpal), M5 (5th metacarpal) zones; Midfoot is represented by the MF zone; Hindfoot is represented by the medial (MH) and lateral zones (LH).

Fig 2. Statokinesiogram of one representative participant from the sighted group and one representative participant from the blind group.

Recordings from the sighted participant in the open-eye (A) and closed-eye condition (B), and from a visually impaired (blind) participant in the open-eye (C) and closed-eye (D) conditions.

Fig 3. Heatmap of the plantar pressure measurements obtained from the participants whose balance control data are shown in Fig 2.

(A) Sighted participant. The pressures are distributed from the hallux to mid-lateral foot and in the heel. (B) Visually impaired participant. The pressure distribution occurs mainly in the hallux, all the metatarsal region of the left foot and in the heel.