Table 2. Orbital anatomical structure mapping.

Specific level 3 orbital system			Related level 1 and 2 systems
Subdivisions	ID	Additional description	Code	Region	Subregions	Code
Orbital rims
Superior	1		Rs	Cranial vault	Frontal bone	94F
Medial	2		Rm	Cranial vault	Frontal bone	94F
Medial	3	Frontonasal maxillary processes	Rm	Midface	UCM	92U
Inferior	4	Part of ICM	Ri	Midface	ICM	92I
Inferior	5	Part of zygomatic body	Ri	Midface	Zygoma	92Z
Lateral	6	Part of zygoma but not zygomatic body	Rl	Midface	Zygoma	92Z
Lateral	7	Area of zygomaticofrontal suture	Rl	Midface	Zygoma	92Z
Orbital walls
Superior	8	Anterior section of orbita	W1s	Skull base	Anterior	93Os	93A
Medial	9	Anterior section of orbita (including the lacrimal bone)	W1m	Midface		92Om
Inferior	10	Anterior section of orbita	W1i	Midface		92Oi
Inferior	11	Anterior section of orbita (including part of zygoma)	W1i	Midface	Zygoma	92Oi	92Z
Lateral	12	Anterior section of orbita	W1l	Midface	Zygoma	92Ol	92Z
Lateral	13	Area of zygomaticosphenoidal suture (greater wing of sphenoid)	W1l	Midface	Zygoma	92Ol	92Z
Superior	14	Midorbitb	W2s	Skull base	Anterior	93Os	93A
Medial	15	Midorbitb	W2m	Midface		92Om
Inferior	16	Midorbitb (including the palatine bone)	W2i	Midface		92Oi
Lateral	17	Midorbitb (greater wing of sphenoid)	W2l	Midface		92Ol	93M
Orbital apexc
	18	Lateral wall (greater wing of sphenoid)	Al	Skull base	Middle	93Oa	93M
	19	Superior wall (lesser wing of sphenoid)	As	Skull base	Anterior	93Oa	93A
	20	Medial wall	Am	Skull base	Sphenoid bone	93Oa	93S

Abbreviations: ICM, intermediate central midface; UCM, upper central midface.

Note: ID (orbital structure ID as presented in Fig. 2).

^aCorresponding to “anterior third.”

^bCorresponding to “middle third.”

^cCorresponding to “posterior third.”