Body balance under ametropic conditions induced by spherical lenses in an upright position

[Purpose] To investigate the changes in body balance under ametropic conditions induced by spherical lenses in an upright position. [Subjects and Methods] Twenty subjects (10 males, 10 females) of average age 23.4 +/- 2.70 years participated and they were fully corrected by subjective refraction. To induce ametropic conditions (binocular myopia and hyperopia), lenses of +/- 0.50 D, +/- 1.00 D, +/- 1.50 D, +/- 2.00 D, +/- 3.00 D, +/- 4.00 D and +/- 5.00 D were used. General stability (ST), fall risk index (FI), and sway path (SP) were analyzed through changes in synchronization of left/right and toe/heel, as measured by the biofeedback system, TETRAX. Measurement was performed for 32 seconds for each condition. [Results] ST increased significantly from +0.50 D-induced myopia and from -1.00 D-induced hyperopia as compared with corrected emmetropia. FI increased significantly from +4.00 D-induced myopia and from -1.50 D-induced hyperopia as compared with corrected emmetropia. In SP, which means a change of body balance, toe/heel was significantly greater than left/right in all ametropic conditions. SP of right/left synchronization was not affected by the side of the dominant eye. [Conclusion] An uncorrected hyperope may cause subjects to have a higher risk of falling than an uncorrected myope. Therefore, clinical specialists should consider the refractive condition, especially hyperopia, when analyzing body balance.