Abstract:
A study was carried out to examine how the ranges of uncertainty of correcting cylinder axis and power were affected by Jackson Crossed Cylinder (JCC) lens power and by test chart design for low vision and normal vision patients. Twenty subjects were selected for Low Vision (LV), Older Normal (ON) and Young Normal (YN) groups. Subjects viewed either a Bailey-Lovie distance letter chart or a chart containing rings of dots of decreasing diameter in a Bull's eye pattern. Subjects were asked to choose the 'clearer and darker' view on each JCC flip. An 'equal' response was allowed when no difference between the two views was observed. Although neither chart type nor NCC lens power had a significant effect on the ranges of uncertainty for cylinder axis and cylinder power, there were significant differences in the results due to age and visual acuity (subject group).
