Download Eye Notes

Eye Notes
I.
II.
Accessory Structures of the eye:
a. Eyelids – aka. Palpebral
i. Meets at medial and lateral canthus
b. Eyelashes
i. Meibomian glands – modified sebacious glands produce an
oily secretion to lubricate the eye
1. Chalazion - inflammation
ii. Ciliary glands – modified sweat glands between the
eyelashes
1. Sty - inflammation
c. Conjunctiva: membrane that lines the eyelids
i. Connects to the surface of the eye
ii. Secretes mucus to lubricate the eye
1. Conjunctivitis – inflammation of – sometimes known as “pink eye”
d. Lacrimal apparatus
i. Lacrimal gland – produces lacrimal fluid
ii. Lacrimal canals – drains lacrimal fluid from eyes
iii. Lacrimal sac – provides passage of lacrimal fluid towards
nasal cavity
iv. Nasolacrimal duct – empties fluid the nasal cavity
v. Functions:
1. Dilute salt solution (tears)
2. Contains antibodies and lysozyme
3. Protects, moistens, and lubricates the eye
4. Empties into the nasal cavity
e. Extrinsic Eye muscles
i. Six eye muscles attach to the outer surface of the eye
ii. Produce gross eye movements
iii. Rectus muscles: lateral, medial, superior, inferior
iv. Oblique muscles: inferior, superior
Structure of Eye
a. The wall is composed of three tunics
i. Fibrous tunic – Outer layer (Sclera)
ii. Vascular tunic (uvea) – middle layer (Choroid)
iii. Sensory tunic – inside layer (Retina)
b. The Fibrous Tunic
i. Sclera: White connective tissue layer
1. Seen anteriorly as the “white of the eye”
ii. Cornea: Transparent, central anterior portion
1. Allows for light to pass through
2. Repairs itself easily
3. The only human tissue that can be transplanted without fear of rejection
c. Vascular Tunic:
d.
e.
f.
g.
i. Choroid – posterior portion
1. Blood-rich nutritive tunic
2. Dark pigment prevents light from
scattering
ii. Ciliary body – anterior
1. Smooth muscle
2. Attached to lens
iii. Iris: Pigmented layer that gives eye color
1. Pupil – rounded opening in the iris
for light passage
2. Circular & radial fibers regulate opening
Sensory Tunic (Retina)
i. Contains receptor cells (photoreceptors)
1. Rods & Cones
ii. Leave the retina toward the brain through the optic nerve
iii. Rods:
1. Allow dim light vision and peripheral vision
2. Edges of Retina
3. Perception is all in gray tones
iv. Cones:
1. Allow for detailed color vision
2. Densest in the center of the retina
v. Fovea centralis
1. Area of the retina with only cones
2. Area of greatest visual acuity
vi. Optic disk (Blind Spot)
1. No photoreceptor cells,
2. Site of optic nerve leaving eyeball
Lens
i. Biconvex crystal-like structure
ii. Held in place by a suspensory ligament attached to the ciliary body
iii. Cataracts: clouding of lens
Aqueous humor in Anterior Segment
i. Watery fluid found in chamber between the lens and cornea
ii. Similar to blood plasma
iii. Helps maintain intraocular pressure
iv. Provides nutrients for the lens and
cornea
v. Reabsorbed into venous blood
1. Blocked drainage = glaucoma
Vitreous humor: Gel-like substance behind the
lens
i. Keeps the eye from collapsing
ii. Lasts a lifetime and is not replaced
iii. Keeps retina firmly against wall of
eyeball