Tiny Bones Bearing Tear Ducts: A Guide to Lacrimal Bones and Their Functions

Introduction

Lacrimal bones, situated in the medial wall of each eye's orbit, are the smallest and most fragile bones in the human skeleton. These tiny, plate-like structures play a crucial role in draining tears from the surface of the eye into the nasal cavity. This process, known as lacrimation, is essential for maintaining eye health and comfort.

Anatomy of Lacrimal Bones

Size and Shape: Lacrimal bones are approximately 15-20 mm tall and 10-12 mm wide. They are thin, triangular or rectangular in shape, with a somewhat concave posterior surface.

Location: Lacrimal bones are located in the anteromedial angle of the orbit, between the frontal bone superiorly and the maxilla laterally. They articulate with these two bones, as well as with the ethmoid bone posteriorly.

Lacrimal Crest and Groove: The anterior surface of the lacrimal bone features a vertical ridge known as the lacrimal crest. This crest, along with the adjacent lacrimal groove on the frontal bone, forms a channel for the nasolacrimal duct. The nasolacrimal duct is a narrow passageway through which tears drain from the eye into the nasal cavity.

Lacrimal Fossa: The posterior surface of the lacrimal bone contains a shallow depression called the lacrimal fossa. This fossa is the site of attachment for the lacrimal sac, a thin-walled sac that collects tears before they enter the nasolacrimal duct.

Functions of Lacrimal Bones

Lacrimal bones primarily serve two functions:

1. Draining Tears: The lacrimal crest and groove, along with the nasolacrimal duct, facilitate the drainage of tears from the eye. Tears are produced by the lacrimal glands, located above the outer corner of each eye. They wash over the surface of the eye, lubricating it and removing foreign particles. The tears then drain through the lacrimal ducts, which empty into the lacrimal sac, and finally into the nasolacrimal duct.

   

2. Protecting the Lacrimal Sac: Lacrimal bones provide protection for the lacrimal sac, which is a vulnerable structure. The bones shield the sac from external trauma and help maintain its integrity.

Clinical Significance

While lacrimal bones are typically not associated with major medical issues, they can be involved in certain conditions:

• Dacryocystitis: Inflammation of the lacrimal sac can lead to pain, swelling, and difficulty draining tears. Dacryocystitis can be caused by infections, blockages, or other underlying conditions.
• Lacrimal Bone Fractures: Lacrimal bones, being fragile, can be susceptible to fractures due to trauma. Fractures of these bones can affect the drainage of tears and may require surgical intervention.
• Lacrimal Gland Prolapse: The lacrimal gland can protrude forward, resulting in a bulging or sagging of the eyelid. This condition can be caused by age, injury, or certain systemic diseases.

Table 1: Dimensions of Lacrimal Bones

Table 2: Articulations of Lacrimal Bones

Table 3: Structures Associated with Lacrimal Bones

Effective Strategies for Lacrimal Bone Fractures

In cases of lacrimal bone fractures, the following strategies may be employed:

• Observation: Minor fractures may not require active treatment and can be managed with observation and pain relief.
• Closed Reduction: If the fracture is displaced, it may be repositioned using a closed reduction procedure. This involves manipulating the bone fragments back into place under anesthesia.
• Open Reduction and Internal Fixation: In more severe cases, open surgery may be necessary to directly repair the fracture. This involves making an incision to access the bone and using screws or plates to secure the fragments.

How to Step-by-Step Approach for Lacrimal Sac Surgery

Surgery to address conditions affecting the lacrimal sac may involve the following steps:

1. Incision: An incision is made in the skin near the inner corner of the eye.
2. Exposure: The lacrimal sac is identified and carefully dissected from surrounding tissues.
3. Dacryocystorhinostomy: A new opening is created in the nasal cavity to connect the lacrimal sac with the nose. This allows tears to drain more easily.
4. Stent Placement: A small stent may be inserted into the newly created opening to keep it open during the healing process.
5. Closure: The incision is closed with sutures.

Pros and Cons of Lacrimal Surgery

Pros:

• Can resolve blockages and improve drainage of tears.
• May alleviate symptoms of dacryocystitis, such as pain, swelling, and tearing.
• Can be performed on an outpatient basis with minimal recovery time.

Cons:

• May not be effective in all cases.
• Can carry a risk of infection, bleeding, or other complications.
• May leave a small scar near the inner corner of the eye.

FAQs

1. What are the symptoms of lacrimal bone fractures?
Symptoms may include pain, swelling, bruising, and difficulty moving the eye.

2. How are lacrimal bone fractures diagnosed?
Diagnosis typically involves a physical examination and X-rays or CT scans.

3. How long does it take for lacrimal bone fractures to heal?
Healing time varies, but minor fractures usually heal within a few weeks. More severe fractures may take longer.

4. What is the purpose of the lacrimal crest?
The lacrimal crest forms a channel for the nasolacrimal duct, which drains tears from the eye.

5. Can lacrimal bone fractures affect vision?
In severe cases, lacrimal bone fractures can cause double vision or other vision problems.

6. Is lacrimal surgery a common procedure?
Lacrimal surgery is relatively uncommon but may be necessary to address blockages or other conditions affecting the lacrimal system.

Conclusion

Lacrimal bones, the tiny bones bearing tear ducts, play an important role in the proper drainage of tears and the maintenance of eye health. While they are typically not associated with major medical issues, understanding their anatomy and functions can assist in diagnosing and treating conditions that may arise. If you experience any abnormalities related to tear drainage or the inner corner of your eye, it is advisable to consult with an ophthalmologist for further evaluation.