W H CRISP

A further, very delicate test for astigmatic axis, using the cross cylinder with an astigmatic dial and without use of letter charts.

W H CRISP, G H STINE, W. Crisp, 1949, American journal of ophthalmology.

A device for group demonstration of astigmatism tests.

W H CRISP, 1946, American journal of ophthalmology.