Axial length, choroidal thickness, and anterior eye biometrics change significantly during accommodation in downward gaze as a function of time. These changes seem to be caused by the combined influence of biomechanical factors (i.e., extraocular muscle forces, ciliary muscle contraction) associated with near tasks in downward gaze.

The angle of gaze has a small but significant short-term effect on axial length, with greatest elongation occurring in inferonasal gaze. The elongation of the eye appears to be due to the influence of the extraocular muscles, in particular the oblique muscles.

Optical blur in the peripheral retina is known to be highly anisotropic due to nonrotationally symmetric wavefront aberrations such as astigmatism and coma. At the neural level, the visual system exhibits anisotropies in orientation sensitivity across the visual field. In the fovea, the visual system shows higher sensitivity for cardinal over diagonal orientations, which is referred to as the oblique effect. However, in the peripheral retina, the neural visual system becomes more sensitive to radially-oriented signals, a phenomenon known as the meridional effect. Here, we examined the relative contributions of optics and neural processing to the meridional effect in 10 participants at 0°, 10°, and 20° in the temporal retina. Optical anisotropy was quantified by measuring the eye's habitual wavefront aberrations. Alternatively, neural anisotropy was evaluated by measuring contrast sensitivity (at 2 and 4 cyc/deg) while correcting the eye's aberrations with an adaptive optics vision simulator, thus bypassing any optical factors. As eccentricity increased, optical and neural anisotropy increased in magnitude. The average ratio of horizontal to vertical optical MTF (at 2 and 4 cyc/deg) at 0°, 10°, and 20° was 0.96 ± 0.14, 1.41 ± 0.54 and 2.15 ± 1.38, respectively. Similarly, the average ratio of horizontal to vertical contrast sensitivity with full optical correction at 0°, 10°, and 20° was 0.99 ± 0.15, 1.28 ± 0.28 and 1.75 ± 0.80, respectively. These results indicate that the neural system's orientation sensitivity coincides with habitual blur orientation. These findings support the neural origin of the meridional effect and raise important questions regarding the role of peripheral anisotropic optical quality in developing the meridional effect and emmetropization.

Pulmonary functional capacities, vital capacity (VC) maximum voluntary ventilation (MVV), forced expiratory volume in 1 second and FEV 1.0 (per cent VC) of 168 sportsmen belonging to different sports activities and of 10 sedentary individuals have been studied. It was observed that all these pulmonary functional capacities of different groups of sportsmen were higher than those of the sedentary group. The mean VC of the basketball, boxing, cricket, football, hockey and the table tennis groups, the mean MVV of all the groups except the athletic, badminton and football groups, and the mean FEV 1.0 of football, hockey, swimming and volleyball groups were significantly higher than those of the sedentary group. The mean values of all the three pulmonary functional capacities of only the hockey group were found to be significantly higher than those of the sedentary individuals. The available reported pulmonary capacity values, except FEV 1.0 of a few groups of sportsmen studied abroad, were higher than those of their counterparts studied here. These might be due to the ethnic variation as well as the variation in age, body size and level of physical fitness which influence the different pulmonary capacities.

A Shack-Hartmann wavefront sensor was modified to allow measurement of ocular aberrations in downward gaze with binocular fixation. Subjects first performed a control task prior to four different trials involving a distance task or a near task (accommodative demand of 2.5 D) performed in primary and downward gaze (25°). Immediately after beginning and then again 5 and 10 min after the commencement of each trial, ocular aberrations were measured. To observe the recovery in ocular aberrations following each test condition, subjects again viewed a distance target in primary gaze and aberration measurements were taken at 0, 5, and 10 min. During the distance task, small but significant changes in refractive power and higher order aberrations were observed in downward gaze compared to primary gaze. The changes in ocular aberrations that occurred in downward gaze recovered almost immediately after shifting gaze from downward back to primary gaze. During the accommodation tasks, there was a significant influence of gaze for changes in primary spherical aberration C(4, 0) [p=0.004] and secondary spherical aberration C(6, 0) [p=0.02]. There was also a significant gaze by time interaction (p=0.04) for changes in C(6, 0). These findings show that ocular aberrations change from primary to downward gaze, particularly during accommodation.