• The pigmented middle layer is called

Uvea Structure

  • The uvea is the pigmented middle layer of the eye.

  • It has three distinct regions:

    • Choroid

      • Forms the posterior part of the uvea.

      • Supplies blood to all layers of the eyeball.

      • Contains brown pigment that absorbs light to prevent visual confusion.

    • Ciliary Body

      • Forms a ring surrounding the lens.

      • Contains smooth muscle fibers (ciliary muscle) that regulate tension in the ciliary zonule, which holds the lens in place.

      • Houses ciliary processes that secrete aqueous humor into the intraocular cavity.

    • Iris

      • The visible colored part of the eye.

      • The central opening is the pupil, which regulates light intake.

      • Pupil size changes with ambient light and emotional state (dilates when frightened or excited).

Retina

  • The retina is the innermost, sensory layer of the eye.

  • Consists of a delicate two-layered membrane:

    • Outer Pigmented Layer

      • Absorbs light and stores vitamin A.

    • Inner Neural Layer

      • Contains photoreceptors that react to light energy.

      • Photoreceptor axons form the optic nerve.

  • Optic Disc (Blind Spot)

    • The point where the optic nerve leaves the eyeball; lacks photoreceptors.

  • Macula Lutea

    • The optic axis of the eye runs through it.

    • Contains the Fovea Centralis which has the highest concentration of photoreceptors for color vision.

    • Disorders affecting the macula significantly impact vision.

Intraocular Cavity

  • The lens and ciliary zonule subdivide the intraocular cavity into an anterior and posterior segment.

Posterior Segment

  • Contains Vitreous Humor:

    • Jelly-like substance surrounded by a thin capsule.

    • Lets light pass through to the retina.

    • Supports the posterior lens surface and holds the retina in place.

    • Contributes to intraocular pressure.

Anterior Segment

  • Filled with Aqueous Humor:

    • Thin, watery liquid formed by the ciliary processes.

    • Released into the posterior chamber behind the iris, travels through the pupil to the anterior chamber.

    • Drained through the scleral venous sinus (canal of Schlemm).

    • Provides waste removal, and supplies nutrients and oxygen mainly to the lens and cornea, and also to the retina.

Lens

  • A biconvex, transparent, flexible, elastic, and avascular structure.

  • Helps focus light onto the retina.

  • Composed of lens fibers filled with a transparent protein called crystalline.