Limbus

 

🌟 What Is the Limbus?

The limbus (or corneoscleral limbus) is the border area between the cornea and the sclera. It's also the junction where the conjunctiva, corneal epithelium, and sclera meet.

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📚 Anatomical Features of the Limbus:

1. Location:

   • Forms a ring around the cornea (about 1–2 mm wide)

   • Lies between:

     • Transparent cornea (centrally)

     • Opaque sclera (peripherally)

2. Structures Found in the Limbus:

   🧬 Palisades of Vogt

   • Radial ridges in the limbal area

   • Contain limbal stem cells, which are essential for corneal epithelial regeneration

   • More prominent in the superior and inferior limbus

   💧 Canal of Schlemm

   • Located in the deep limbal region, just inside the sclera

   • Drains aqueous humor from the anterior chamber to the venous system—critical for intraocular pressure (IOP) regulation

   🌀 Trabecular Meshwork

   • Lies just anterior to the canal of Schlemm

   • Filters aqueous humor before it exits through Schlemm’s canal

   🧱 Conjunctival and Tenon’s Capsule Insertion

   • The conjunctiva and Tenon’s capsule insert into the limbus and help support ocular surface integrity

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🔌 Blood and Nerve Supply:

• Supplied by anterior ciliary arteries forming a superficial and deep limbal arcades

• Rich sensory innervation from the long ciliary nerves (branch of the ophthalmic division of CN V)

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🔎 Functions of the Limbus:

• Serves as a stem cell reservoir for corneal epithelium

• Acts as a barrier to prevent conjunctival overgrowth onto the cornea

• Regulates aqueous humor outflow through Schlemm’s canal and trabecular meshwork

• Plays a role in immune surveillance at the ocular surface

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🧾 Clinical Relevance:

• Limbal Stem Cell Deficiency (LSCD): Leads to corneal opacification, neovascularization, and vision loss

• Pterygium: Abnormal growth of conjunctiva over the limbus and onto the cornea

• Surgical Landmark: Important in trabeculectomy, LASIK, and pterygium excision