Uvea

 

🌈 What Is the Uvea?

The uvea lies between the sclera (outer fibrous layer) and the retina (inner neural layer). It consists of three major components, from front to back:

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📚 Anatomy of the Uveal Tract:

1. Iris

• Location: Anterior portion of the uvea; visible colored part of the eye

• Function: Regulates light entry by adjusting pupil size (via sphincter and dilator muscles)

• Key Parts:

  • Pupil (central aperture)

  • Stroma (contains pigment cells and blood vessels)

  • Sphincter pupillae (parasympathetic control – constriction)

  • Dilator pupillae (sympathetic control – dilation)

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2. Ciliary Body

• Location: Continuous with the iris; lies behind it and forms a ring around the lens

• Function:

  • Produces aqueous humor

  • Anchors zonules (suspensory ligaments of the lens)

  • Contains ciliary muscle (for accommodation—focus adjustment)

• Key Parts:

  • Pars plicata (anterior, folded part – active in aqueous humor production)

  • Pars plana (posterior, flat part – often used for surgical access)

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3. Choroid

• Location: Between the sclera and retina, extending from the ora serrata to the optic disc

• Function:

  • Supplies oxygen and nutrients to the outer retina

  • Contains melanin to absorb stray light

• Key Features:

  • Highly vascular

  • Contains Bruch’s membrane (inner barrier with retina)

  • Rich in melanocytes and blood vessels

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🧬 Functions of the Uvea:

• Provides nutrition to eye tissues (especially retina and lens)

• Controls light entry (via iris)

• Involved in accommodation (via ciliary muscle)

• Regulates intraocular pressure (through aqueous humor dynamics)

• Plays a major role in ocular immune responses