Table 2. The frequency distribution for number of retinal images in an image set (N = 7905 image sets).

No. retinal images of any quality in image set	No. image sets (%)
1	34 (0.43)
2	48 (0.61)
3	152 (1.92)
4	339 (4.29)
5	7332 (92.8)
No. retinal images with acceptable quality among sets with at least 1 image	No. image sets (%)
0	57 (0.72)
1	104 (1.32)
2	167 (2.11)
3	408 (5.16)
4	1126 (14.2)
5	6043 (76.5)