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Lacrimal bone

The lacrimal bone is a small, thin, rectangular bone located in the anteromedial wall of the orbit. Despite being one of the smallest bones in the face, it plays an essential structural role in forming the lacrimal fossa, which houses the lacrimal sac, and contributes to the framework guiding tear drainage into the nasolacrimal duct.

It forms part of the orbit, nasal cavity, and lacrimal drainage system, making it a critical anatomical landmark in both ophthalmology and ENT surgery. Because of its thinness and proximity to the lacrimal sac, the bone is vulnerable to trauma, inflammatory extension, and surgical manipulation during dacryocystorhinostomy (DCR).

Synonyms

  • Os lacrimale

  • Medial orbital wall lamina

Location and Structure

  • Position: Anterior part of the medial orbital wall

  • Shape: Thin, rectangular plate with smooth orbital surface

  • Key features:

    • Lacrimal groove: A vertical depression housing the lacrimal sac

    • Posterior lacrimal crest: Sharp crest forming posterior boundary of lacrimal fossa

    • Anterior lacrimal crest (frontal process of maxilla): Lies just anterior, together forming the fossa

  • Articulations:

    • Maxilla (anterior and inferior)

    • Ethmoid bone (posterior)

    • Frontal bone (superior)

    • Inferior nasal concha (inferior)

Relations

  • Anteriorly: Frontal process of maxilla and anterior lacrimal crest

  • Posteriorly: Lamina papyracea (ethmoid bone)

  • Superiorly: Frontal bone forming part of orbit roof

  • Inferiorly: Maxilla and the nasolacrimal duct region

  • Medially: Nasal cavity (lateral nasal wall)

  • Laterally: Orbit and lacrimal sac fossa

Attachments

  • Contributes to the lacrimal fossa, anchoring the lacrimal sac

  • Supports lacrimal fascia and periosteum

  • Forms part of the bony canal for the nasolacrimal duct

Function

  • Provides bony framework for tear drainage pathway

  • Forms part of the medial orbital wall

  • Stabilizes lacrimal sac and duct

  • Contributes to structural integrity of the medial orbit

MRI Appearance

T1-weighted images:

  • Lacrimal bone appears as low signal (dark) due to dense cortical bone

  • Adjacent orbital fat is bright, providing contrast

  • Lacrimal sac: intermediate to mildly bright fluid signal

  • Nasolacrimal duct: intermediate signal depending on mucosa and secretions

T2-weighted images:

  • Bone: very low signal

  • Lacrimal sac fluid: bright hyperintense

  • Surrounding soft tissues: intermediate signal

  • Nasolacrimal duct: bright if fluid-filled; low-to-intermediate if mucosa-dominant

STIR:

  • Bone: dark

  • Adjacent fat suppressed

  • Soft tissues of lacrimal fossa and lacrimal sac appear intermediate

  • Fluid within sac or duct appears bright

3D T2 (SPACE / CISS):

  • Bone: sharply demarcated dark structure

  • Lacrimal sac and duct: very bright fluid signal, allowing high-resolution visualization

  • Excellent delineation of orbital and lacrimal pathways

  • Useful for detecting subtle anatomic variations

CT Appearance

Non-Contrast CT:

  • Lacrimal bone: high-attenuation, thin, sharply defined cortical plate

  • Lacrimal fossa structures clearly outlined

  • Excellent depiction of:

    • Fractures

    • Nasolacrimal canal

    • Ethmoid-lacrimal junction

    • Medial orbital wall thickness

  • Surrounding soft tissue: intermediate density

Post-Contrast CT:

  • Bone remains non-enhancing

  • Lacrimal sac and mucosa enhance mildly

MRI image

Lacrimal bone MRI axial image-img-00000-00000

CT image

Lacrimal bone

CT VRT 3D image

Lacrimal bone 3d