Table 1.

Trial conditions.

Trial	Measuring	Size	Curvature	Fading	Ambient light	No. of scans
1	Size	Varied in 0.5-mm increments between 5 mm and 9 mm	Flat	None	500 lux	9
2	Fading	7 mm	Flat	Varied in 10% increments between 0% and 90%	500 lux	10
3	Curvature	7 mm	0 mm (flat), 10 mm, 15 mm, 17 mm	None	500 lux	4
4	Ambient light	7 mm	Flat	None	5, 20, 150, 500 lux	4