Updated: 2/2/2021

Eye Anatomy

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Topic
Introduction
  • The structures of the eye
    • cornea
      • a transparent structure that allows light to enter the eye
    • pupil
    • iris
      • covered by the conjunctiva, a transparent mucous membrane
        • remember that the conjunctiva lines the inside of the eyelids as well, up to the limbus
        • clinical correlate
          • conjunctivitis
            • which describes inflammation of the conjunctiva
    • sclera
    • limbus  
      • which is the border of the cornea and sclera
    • medial and lateral canthus
  • Light enters the eye through the cornea and lens which results in
    • an image (inverted and reversed) being formed in the retina  
      • the area on the retina with the highest visual acuity is the fovea, which is surrounded by the macula
      • medial (nasal) to the fovea is the optic disc, which  
        • is where axons exit forming the optic nerve (cranial nerve II)
          • note that the optic nerve does not have photoreceptors over it, resulting in a small blind spot
      • photoreceptors
        • there are two classes
          • rods
            • provides vision in a low-level light environment
            • does not detect color
          • cones
            • highly represented in the fovea
            • detect color
      • choroid
        • is a vascular layer of the eye
      • ciliary body
        • is found between the choroid and the iris and is composed of the
          • ciliary muscle
            • which is controlled by the parasympathetic fibers in the oculomotor nerve in order to
              • contract, resulting in miosis
          • ciliary processes
            • which have zonular fibers extending from this structure to the lens forming
              • the suspensory ligament
  • Anterior chamber
    • describes the area behind (posterior) to the cornea and in front (anterior) to the iris
  • Posterior chamber
    • describes the area posterior to the iris and anterior chamber
  • Aqueous humor pathway 
    • the ciliary body produces aqueous humor into the posterior chamber which
      • flows through the space between the lens and iris into the
        • anterior chamber and finally drains into the
          • trabecular meshwork and then canal of Schlemm
          • uveoscleral pathway
  • Blood supply
    • an arterial source is from
      • the short posterior, long posterior, and anterior ciliary arteries
      • the central retinal artery which supplies the optic nerve
    • venous drainage is from
      • the vorticose veins
      • central retinal veins

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Questions (1)

(M3.OP.16.33) A 32-year-old construction worker presents to the emergency room with severe right eye pain. He states that the pain started two days ago while he was drilling. He has been experiencing severe pain, redness, and watering of the right eye since then. His eye is shown in Figure A. Bacterial culture will most likely reveal which organism?

QID: 102787
FIGURES:
1

Streptococcus viridans

12%

(1/8)

2

Coagulase-negative staphylococcus

0%

(0/8)

3

Neisseria gonorrhoeae

0%

(0/8)

4

Staphylococcus aureus

62%

(5/8)

5

Streptococcus epidermidis

0%

(0/8)

M 10 E

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