During transillumination of the antrums, it will be found that when the lower lids are pulled down some light is normally transmitted to the soft areolar tissue below the globe and behind the infraorbital ridge. This is especially likely to occur in cases in which transillumination is good enough to light the pupil, but the light under the globe appears in some cases in which the pupil is not illuminated.
This internal infraorbital light appears as a crescent. The horns of the crescent vary from short and rounded to long and sharp, according to how much light comes through the roof of the antrum. More minute differences can be determined by comparisons of these two fields than by ordinary facial comparisons of transillumination, and the results give some indication as to the condition of the roofs of the respective antrums. The status of the horns of the crescent, moreover, is