In the higher orders the fluting tends to become obscured by flattening of the wing-membrane or the development of secondary curvatures imposed by mechanical considerations.

It is free of coma and spherical aberration at a nearly flat focal plane if the primary and secondary curvature are properly figured, making it well suited for wide field and photographic observations.

A consequence of the normal lordotic curvatures of the vertebral column, (also known as secondary curvatures) is that there are differences in thickness between the anterior and posterior part of the intervertebral disc.