1. Anatomy of the Eyeball

2. Cavities of the Eyeball
separated by the lens
anterior
posterior

3. Anterior Cavity between lens and cornea
filled with aqueous humor (watery fluid)
Divided into:
- anterior chamber (anterior to iris)
- posterior chamber (posterior to iris)

4. Posterior Cavity between lens and retina
filled with vitreous body (jelly-like substance)
also called vitreous chamber

5. Lens elastic, transparent, biconcave structure
separates anterior and posterior cavities of eyeball
suspended from ciliary body by suspensory ligaments
tension on suspensory ligaments controls shape of lens

6. Layers of Eyeball (tunics)
fibrous - outer
- sclera
- cornea
vascular - middle
- choroid
- ciliary body
- iris
retina - inner nervous

7. Layers of Eyeball
iris
sclera
cornea
pupil
choroid
ciliary body
retina

9. Sclera - outer fibrous “white of the eye” outermost protects eye
thick, tough connective tissue
capsule that maintains shape of eye
serves as point of attachment for extrinsic muscles
makes up 5/6 of sclera

10. Cornea - outer fibrous
anterior 1/6 of fibrous tunic; continuous with sclera
bulges forward, forming convex surface
- refracts light rays as they enters eye
transparent - allows light rays to pass
lacks blood vessels
receives nutrition from lymph
has five layers

11. Cornea - outer fibrous (cont.)
has touch and pain receptors
injury causes scarring
most exposed part of eye
great ability to repair itself
only tissue that can be transplanted from person to person without rejection

12. Scleral Venous Sinus also called canal of Schlemm
junction of sclera and cornea
drains aqueous humor from eyeball

13. Choroid - middle vascular layer
vascular layer; blood rich
contains dark pigment produced by melanocytes
- absorbs pigment and prevents scatter of light after it passes through retina
anterior portion becomes ciliary body and iris

14. Ciliary Body - middle vascular layer
thickest part of vascular tunic
forms internal ring in anterior part of eyeball
within are projections or folds called ciliary muscles
- secrete aqueous humor into anterior cavity
lens is attached via suspensory ligaments

15. Iris - middle vascular layer
extends out from ciliary body
anterior to lens
thin diaphragm of connective tissue
seen from outside as colored portion of eye
has rounded opening called pupil
regulates amount of light entering posterior cavity of eyeball through pupil

16. Pupils bright light or close up - pupils constrict
dim light or distance - pupils dilate

17. suspensory ligaments
anterior
chamber
lens
cornea
posterior
chamber
pupil
iris

18. Retina - inner nervous layer
light sensitive
is where light rays form an image
image travels via optic nerve to cerebral cortex
if image is not focused correctly, corrective glasses or lenses are required
contains photoreceptors
- rods and cones

19. Photoreceptors rods - 20 million - recognize gray tones and dim light
cones
- 6 million - recognize primary colors
together they interpret intermediary colors
in moonlight only rods are functioning; therefore we cannot see colors

20. Fovea Centralis depressed area in center of macula lutea
- yellowish spot just lateral to optic axis of eyeball
has highest concentration of cones in retina
produces sharpest vision and best color perception

21. Optic Disc also called blind spot medial to optic axis
fibers from ganglion cells exit eyeball to form optic nerve
no photoreceptors; light striking this area produces no image

22. Color Blindness inability to distinguish colors
caused by a lack or deficiency in one of the three cone photopigments
most common type is red-green color blindness
inherited condition affecting males more often than females - sex-linked

23. Intraocular Pressure
caused when scleral venous sinus is obstructed and reabsorption of aqueous humor cannot keep up with its secretion
pressure in chambers pushes lens back and puts pressure on vitreous body which in turn presses on retina which obstructs blood supply

24. Intraocular Pressure (cont.)
retinal cells die and optic nerve may atrophy causing blindness (glaucoma)
symptoms usually go unnoticed until damage is irreversible
disease can be detected by use of tonometer used to measure intraocular pressure

25. Glaucoma group of eye diseases
characterized by an increase in intraocular pressure
pressure causes pathological changes in optic disk and visual field defects

26. Normal Flow of Intraocular Fluid

27. Abnormal Flow of Intraocular Fluid (most common type)
egress is partially blocked causing increased accumulation of fluid causing increase pressure and eventual blindness

28. Acute Closed-Angle Abnormal Flow of Intraocular Fluid
egress is totally blocked causing permanent blindness suddenly

29. Accessory Structures eyelids lacrimal apparatus extrinsic muscles
cranial nerves

30. Eyelid Composed of: - skin covers outer surface
- conjunctiva covers inner surface of eyelid and anterior surface of eyeball (except cornea)

31. Eyelid (cont.) Composed of: - tarsal glands
modified sebaceous gland (oil)
open at edge of each eyelid
also called Meibomian glands
- muscles
orbicularis oculi - surrounds eye
levator palpebrae - in upper eyelid

32. Lacrimal Apparatus lacrimal gland superior and inferior canaliculi
lacrimal sac
nasolacrimal duct

33. Lacrimal Gland located in upper portion of each orbit
secretes constant flow of tears
- wash anterior surface of eyeball
- maintain moist and clean environment for cornea and conjunctiva
- contain antibacterial enzyme lysozyme that helps prevent eye infections

34. Superior and Inferior Canaliculi
collect tears after they have washed over eyeball
Lacrimal Sac
collects tears from canaliculi
Nasolacrimal Duct
connects lacrimal sac to nasal cavity where tears are swallowed

35. Extrinsic Muscles arise from bones of the orbit
inserted into broad tendons on sclera
Six extrinsic eyeball muscles:
lateral rectus medial rectus
superior rectus inferior oblique
inferior rectus superior oblique

36. superior oblique
superior rectus
trochlea
inferior
oblique
lateral
rectus
(cut)
medial rectus
inferior
rectus

37. Primary Actions of the Eye Muscles
abduction
adduction
elevation
depression

38. Abduction
contraction of lateral rectus moves pupil away from nose
Adduction
contraction of medial rectus moves pupil towards nose

39. Elevation
contraction of superior rectus or inferior oblique muscles moves pupil upward
Depression
contraction of inferior rectus or superior oblique muscles moves the pupil downward

40. Cranial Nerves of Eyeball Innervation
oculomotor (III)
- branches innervate superior rectus, medial rectus, inferior oblique, and inferior rectus
trochlear (IV)
- innervates superior oblique
abducens (VI)
- innervates the lateral rectus