Orbital Anatomy (Questions)

When studying ophthalmology, it can be hard to know exactly what to spend time memorizing and what to ignore.  When I asked my senior residents for advice when studying, they provided the very unhelpful advice:  "learn everything."  Of course, it took a long while to realize that to some degree they were right - every detail we remember can be extremely helpful years down the road.  At the same time, to borrow from George Orwell, "all [ophthalmology information] is equal; but some are more equal than others."

For those people who prefer to study by answering questions, these articles will list questions you can use to guide your study.  Answers will be provided separately.  Where possible, I will try to provide a few real-world reasons for knowing this information.  For those who are interested in a book that is formatted in a very similar fashion, check out Tamesis' Ophthalmology Board Review: Pearls of Wisdom.

As a disclaimer, I am not intentionally copying questions directly from Tamesis or any other review resource, nor am I attempting to reproduce questions from the OKAP or Board exams - while there will most likely be many similar questions (since the whole point is to help remember all of the important aspects of ophthalmology), the organization, phrasing, and commentary are my personal take unless otherwise cited.

Orbital Anatomy

Orbital Dimensions

  • What is the volume of the orbit?
  • What is the height of the orbit?
  • What is the width of the orbit?
  • What is the depth of the orbit?
  • Where is the maximum orbital width located?
  • What is the intraorbital distance?

Orbital Bones

  • What are the bones of the orbit?
  • What bone(s) comprise the superior orbital margin?
  • What bone(s) comprise the medial orbital margin?
  • What bone(s) comprise the inferior orbital margin?
  • What bone(s) comprise the lateral orbital margin?
  • What bone(s) comprise the orbital roof?
  • What bone(s) comprise the lateral orbital wall?
  • What bone(s) comprise the orbital floor?
  • What bone(s) comprise the medial orbital wall?
  • What is the lamina papyracea?

Orbital Fossas

As you may recall from anatomy, a bony fossa is a part of the bone that is bowed in ("depression").  There are at least two questions that should be answered for each of the following structures:

  1. What bone(s) comprise the fossa?
  2. What structure(s) are contained within the fossa?

In no particular order:

  • Lacrimal gland fossa
  • Lacrimal (sac) fossa (yes, there is a big difference)
  • Trochlear fossa
    • Where is the trochlear fossa located, relative to the orbital margin?
  • Hypophyseal fossa
  • Pterygopalatine fossa

Orbital "Holes":  Foramina and Fissures

Foramina are holes in bones that specifically contain nerves and/or vessels.  They're different from fissures, which are grooves or spaces in-between bones.

I studied these holes by making sure I knew these three facts:

  1. What bone(s) contain the foramen?
  2. What structure(s) pass through it?
  3. Where is it located (i.e., could I identify it radiographically or during surgery)?

There are several foramina we need to know in orbital anatomy for various reasons:

  • Optic foramen
  • Supraorbital foramen (in some people this is a notch)
  • Anterior ethmoidal foramen
  • Posterior ethmoidal foramen
  • Zygomatic foramen
  • Foramen rotundum
  • Foramen ovale

There are two major orbital fissures that we need to know intimately.  Since many clinical applications are related to knowing these anatomical structures, this would probably be an important concept to master.

  • Superior orbital fissure
  • Inferior orbital fissure

Orbital "Holes":  Ducts and Canals

I categorized ducts and canals separately because they tend to be much smaller holes in the bone than the foramina and fissures.  Again, these holes tend to contain some pretty critical structures that you either want to intentionally avoid or find as part of your clinical evaluation or in surgery.

  • Nasolacrimal duct
  • Infraorbital canal
  • Pterygoid canal


While many of us probably won't be working within the sinus very often, we still need to know the anatomical relationship between the sinuses and the orbit.

  • Ethmoid sinus
  • Maxillary sinus
  • Sphenoid sinus
  • Frontal sinus

 References, Resources, and Additional Reading

  1. Basic and Clinical Science Course, Section 2:  Fundamentals and Principles of Ophthalmology, 2010-2011 Edition.  American Academy of Ophthalmology.  San Francisco:  2010.
  2. Tamesis R, ed. Ophthalmology Board Review: Pearls of Wisdom, 2nd ed. McGraw-Hill, 2005.

Did I miss any structures?  Do you have other questions you think should be added to this list?  Leave a comment!