Observations of Normal Optic Foramen in Korean

ABSTRACT

The optic canal begins to be formed by the fusion of two roots of the lesser wing of sphenoid. It is a funnel shaped tube measuring about 4~9 mm long and 4~6 mm broad. But the canal shows considerable variations in its caliber. The optic canal attains its full size at 3 and 5 years of age. Since the radiograms of the optic canal was taken in the living human subject first by Rhese (1911), various radiographic methods have been revised by many other scholars. The development of the radiographic technique made it possible not only to evaluate the morphology (size, shape and its symmetry) of the canal but also to find its pathology such as fracture, fissure, callus formation and abnormal shadow. In the radiogram of the optic foramen the most shows a quadrant of a circle in shape, being more or less elliptical, circular or quadrangular. The two principal diameters were measured the A diameter, which is principal downward and outward at an angle, and the B diameter, which is at right angle to A (Goalwin, 1924). The average A diameter of normal adult optic foramen was reported to be 4.3 mm and the B 4.4 mm by Goalwin (1926, 1927). The average transverse diameter of normal optic foramen was said to be 5.5 mm by Harwood-Nash (1970). In Korea, normal Korean optic canal has never been surveyed roentgenologically. Theshape, size and symmetry of 312 normal optic foramen of 156 Korean were studied in the radiogram taken by Goalwin's method from January, 1974 to December, 1979. 1. The shape of the optic foramen was oval (42.4%), circular (28.4%), a quadrant of a circle (19.8%) and elliptical (9.4%). And 86% of the foramen showed symmetrical in shape. 2. The size of the optic foramen was as follows; A diameter is 4.73 mm (right), 4. 76mm (left); B diameter 5.00 mm (right), 5.06 mm (left); horizontal diameter 4.71 mm (right), 4.65 mm (left); vertical diameter 4.93 mm (right), 4.97 mm (left). Differnce between the diameters of the foramen measured by means of roentgenography and the actual diameter calculated by Goalwin's formula was 0.03~0.04 mm. 3. The diameter of optic foramen seemed to attain its full size at 5 years of age. The average size of each diameter before age 5 was shorter than that after age 5 by 0.44~0.96 mm (p<0.006). 4. There were no appreciable variations in size and shape depending on sex. 5. The optic foramen was same on the two sides (13.8%). Differences of 5% or less were noted in 41.8%; differences of 20% or less shown in 89.1%. 6. Differences between the diameters (A, B, vertical of the foramen of the right and that of the left were less in the symmetrical foramen than asymmetrical (p<0.04).