One of the problems with the Cormack and Lehane classification is that very different views may be graded the same. For example, Grade 2 includes both a view of nearly 50% of the vocal cords (easy), and a view of only the tips of the arytenoids cartilages (pretty difficult).

Several modifications of this classification have been suggested. In one modification, described by Cook and Cranshaw, Grade 2 and 3 are subdivided (Table 1).

Grade 2a	Part of the vocal cords are visible
Grade 2b	Only posterior elements (arytenoids or of the posterior commisure) of glottis visible
Grade 3a	Only epiglottis seen, can be lifted from the posterior pharyngeal wall
Grade 3b	Only epiglottis seen, cannot be lifted from posterior pharyngeal wall

Table 1 Subdivions of Grades 2 and 3