 ### Description

The ONO angle (Outer canthus, Nasal, Outer canthus) is the angle subtended by 2 lines connecting the base of the nose to each outer canthus. It provides an estimate of spacing between the eyes and the upper facial height.

Patient selection: Data is available for children from 5 to 11 years of age

Technique:

(1) The child may either be sitting erect with the eyes pointing forward, or lying face up with eyes pointing vertically.

(2) The angle can be measured from a photograph of the child in the proper position.

 age +2 SD +1 SD mean -1 SD -2 SD 5 105 100 95 89.5 84 6 104.7 99.7 94.5 89 83.6 7 104.2 99.1 93.8 88.4 83 8 103.6 98.3 92.9 87.6 82.3 9 102.8 97.5 92 86.8 81.4 10 101.9 96.4 91.1 85.7 80.4 11 100.9 95.5 90.4 84.8 79.5

from Figure 7.91 based on the data of M Patton from 1987

This data can be approximated by second order equations derived in JMP.

+2 SD line=

= (-0.07024 * ((age in years)^2)) + (0.434524 * (age in years)) + 104.6

+1 SD line=

= (-0.065476 * ((age in years)^2)) + (0.27262 * (age in years)) + 100.34286

mean line=

= (-0.02381 * ((age in years)^2)) - (0.419048* (age in years)) + 97.785714

-1 SD line=

= (-0.053571 * ((age in years)^2)) + (0.0607143 * (age in years)) + 90.557143

-2 SD line=

= (-0.058333 * ((age in years)^2)) + (0.1654762 * (age in years)) + 84.671429

Interpretation - The angle may be abnormal in a child with:

(1) hypotelorism (decreased angle)

(2) hypertelorism (increased angle)

(3) reduced upper facial height (increased angle)

(4) increased upper facial height (decreased angle)