Histology of the Eye - SRS Flashcards
The eye is comprised of two compartments divided by the lens, suspensory ligaments and ciliary body into Anterior and Posterior compartments. Describe the contents of these compartments.
•Anterior compartment
–Filled with aqueous humor
–Contains anterior and posterior chambers separated by the iris
•Posterior compartment
–Filled with vitreous humor
What are the three tissues of the eye?
Corneo-scleral layer (fibrous tunic)
Uveal Layer (Vascular tunic)
Retinal Layer ( Neural Tunic)
What does the corneo-scleral layer make up?
Sclera in posterior (5/6) wall of eye
Cornea in anterior 1/6 of the eye (transparent)
What does the Uveal layer make up?
Choroid in the posterior (5/6) wall of the eye
What are the accessory structures of the eye? (3)
Conjunctiva
Lacrimal Gland
Eyelid
The sclera is the opaque white posterior 5/6 of the eye.
What is it composed of?
Describe the vascularity of the sclera.
Composed of collagen and elastin
Nearly avascular
The cornea is the transparent layer in the anterior 1/6 of the eye. Describe its vascularity and innervation levels.
Avascular
Highly innervated
What are the five layers of the cornea?
- Outer epithelium
- Bowman’s Membrane
- Substantia Propria
- Descemet’s Membrane
- Corneal Endothelium
What structure is shown here?
What are the indicated layers?
Cornea
- Outer epithelium
- Bowman’s Membrane
- Substantia Propria
- Descemet’s Membrane
- Corneal Endothelium
What cell types make up the outer epithelium of the cornea?
Nonkeratinized squamous
What is Bowman’s Membrane?
Thin basal lamina of the cornea
Describe the substantia propria of the cornea
Dense collagenous tissue with sparse keratinocytes
What is descemet’s membrane?
Thick basal lamina of the cornea
What is the role of the corneal endothelium?
- active transport of fluid out of SP
- allowing diffusion of metabolites from aqueous humor
What are the types of refractive error?
Myopia
Hyperopia
What is myopia?
Nearsightedness
What causes myopia?
–Light rays are focused in front of the retina
»Cornea is too curved or
»lens is too powerful for length of globe
What is hyperopia?
Farsightedness
What causes hyperopia?
–Light rays are focused behind the retina
»Lens and cornea too weak for length of globe
LASIK stands for Laser Assisted In-Situ Keratomieusis. What conditions can be treated with this?
Hyperopia and myopia
Describe the procedure for LASIK
- •A corneal flap is raised using a microkeratome
- –About 160 microns thick
- •An ultraviolet or “cool laser” is used to ablate a precise amount of the exposed corneal stroma
- •The flap is irrigated and replaced
- •NO sutures are applied
- –The flap remains in place due to the dehydration pump action of the corneal endothelium
- •Corneal epithelial cells are replaced by mitotic cells found in the periphery, which migrate into the wound
The uveal layer contains the Choroid, which is the posterior pigmented portion of the vascular layer. What are the histological components of the Choroid?
–Loose connective tissue
–Fibroblasts
–Melanocytes