The lacrimal bone is the smallest bone in the human face, roughly the size of a fingernail. You have two of them, one on each side. Each sits at the inner corner of the eye socket, forming part of the wall between your eye and your nasal cavity. Despite its tiny size, the lacrimal bone plays a central role in your tear drainage system, giving tears a bony channel to flow from your eyes down into your nose.
Where the Lacrimal Bone Sits
Each lacrimal bone forms part of the medial wall of the orbit, which is the bony socket that houses and protects the eyeball. This inner wall is built from four bones arranged front to back: the maxillary bone (upper jaw), the lacrimal bone, the ethmoid bone, and the sphenoid bone. The lacrimal bone occupies the front portion of this wall, tucked right behind the bridge of your nose near the inner corner of the eye.
It’s a paper-thin, roughly rectangular plate of bone. Its neighbors matter: it connects to the frontal bone above, the ethmoid bone behind it, and the maxillary bone below and in front. These connections anchor it in place, but the bone itself is fragile. Of all the bones making up the eye socket wall, the lacrimal bone is the thinnest.
Key Landmarks on the Bone
For such a small bone, the lacrimal has several features that make it functionally important.
The posterior lacrimal crest is a vertical ridge running down the outer surface of the bone. This ridge serves as a dividing line. In front of it lies a shallow groove called the lacrimal sulcus, which cradles the lacrimal sac, a small pouch that collects tears before they drain downward.
At the bottom of the bone sits the lacrimal hamulus, a small hook-shaped projection that curves forward. This hook forms half of the bony rim surrounding the opening of the nasolacrimal canal, the passage that carries tears from the lacrimal sac down into the nasal cavity. The frontal process of the maxillary bone completes the other half of this opening. Together, these two structures create a complete bony ring that keeps the drainage channel stable and properly positioned.
How It Supports Tear Drainage
Every time you blink, a thin film of tears spreads across the surface of your eye. Those tears need somewhere to go, and the lacrimal bone provides the structural framework for their exit route. Tears flow from the eye’s surface into tiny openings at the inner corner of each eyelid, travel through small channels into the lacrimal sac (which sits in the groove on the lacrimal bone), and then pass through the nasolacrimal canal into the nose. This is why your nose runs when you cry.
The lacrimal hamulus at the base of the bone is particularly important here. By forming a semicircular edge around the top of the nasolacrimal canal, it directs tears from the sac into the canal with minimal resistance. Without this bony scaffolding, the soft tissue of the drainage system would lack the structural support it needs to keep tears flowing in the right direction.
What Happens When It’s Fractured
Because the lacrimal bone is so thin, it’s vulnerable to fractures, especially in injuries that involve the middle of the face. The most relevant injuries are fractures of the naso-orbito-ethmoid (NOE) complex, the cluster of delicate bones around the bridge of the nose and inner eye socket. These fractures can crush or displace the lacrimal bone and damage the tear drainage structures it supports.
The most common consequence is epiphora, a persistent overflow of tears down the face. When a fracture disrupts the lacrimal sac or the nasolacrimal duct, tears can no longer drain properly and instead spill onto the cheek. Depending on the study, somewhere between 12% and 29% of people with NOE fractures develop symptomatic blockage of the tear drainage system. Simpler nasal fractures carry a much lower risk (about 0.2%), while certain midface fractures fall in between at around 3%.
In cases where the medial orbital wall is fractured in a way that compresses or fragments the lacrimal bone, bone fragments can get pushed into the lacrimal sac itself. This can cause not only constant tearing but also repeated infections of the sac, a condition called dacryocystitis, where the affected eye produces mucus-filled discharge alongside the excess tears.
The Lacrimal Bone in Surgery
The lacrimal bone’s thinness, while a vulnerability in trauma, is actually an advantage in one common surgical procedure: dacryocystorhinostomy, or DCR. This surgery is performed when the tear drainage pathway becomes chronically blocked, whether from injury, infection, or age-related narrowing.
During the procedure, a surgeon creates a new opening between the lacrimal sac and the inside of the nasal cavity, essentially bypassing the blocked duct. To do this, bone needs to be removed. Surgeons typically start by perforating the bone at the junction where the thicker frontal process of the maxilla meets the much thinner lacrimal bone, because the lacrimal bone is far easier to work through. From there, they widen the opening using specialized instruments or a high-speed drill, removing enough bone to expose the lacrimal sac and create a clear pathway for tears to drain directly into the nose.
The fact that the lacrimal bone is so thin makes this step relatively straightforward compared to working through thicker surrounding bones. It’s one of the rare cases in anatomy where a bone’s fragility is a clinical benefit rather than a liability.