1. The Eye and its Appendages
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2. The Eyeball
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3. - the peripheral organ of
vision, is situated in a skeletal
cavity, the orbit
- 1 inch in diameter, 8g. in
weight
- The eyeball is embedded in
orbital fat, separated from it
by a thin fascial sheath
(capsule of Tenon)
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4. Cavities of the Eyeball
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5. 1. Anterior Cavity
- further divided into
anterior chamber and
posterior chamber due to
the position of the iris.
- contains the acqueous
humor produced by the
ciliary process.
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6. 2. Posterior Cavity
- located behind the lens
- contains the vitreous
humor enclosed in
hyaloid membrane
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7. Layers of the Eyeball
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8. The Layers of the Eyeball
1. Fibrous coat - sclera and cornea
2. Vascular coat - choroid, ciliary body and the
iris
3. Neural coat - retina
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9. Sclera
1. The Fibrous Coat
Cornea
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10. A. The Sclera
- relatively hard consistency, is a dense layer which, when
distended by intraocular pressure, maintains the shape of
the eyeball
- external surface is white and smooth and is in contact
with the inner surface of the fascial sheath of the eyeball
- provides passage for nerves of the cornea and vascular
autonomic nerves and attachment for extrinsic eye muscles
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11. B. The Cornea
- is the anterior, projecting transparent part of the
external tunic, and
- its tear film cover is the major site of refraction of
light entering the eye.
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12. Choroid
The Vascular Coat
Ciliary Body
Iris
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13. a. The Choroid
- The choroid is a thin, highly
vascular, dark brown tissue
which lines almost the
posterior five-sixths of the eye;
- it is pierced behind by the
optic nerve and is firmly
adherent to the sclera;
- it is thicker posteriorly;
- internally it is firmly attached
to the retinal pigmented layer.
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14. b. The Ciliary Body
- The ciliary body is directly
continuous with the choroid
behind and with the iris in front
- Internally it shows a scalloped
periphery where it is continuous
with the choroid and retina,
termed the ora serrata.
- The ciliary body is concerned
with the suspension of the lens
and with accommodation
- It is also a major source of
aqueous fluid for the anterior
segment of the eye
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15. c. The Iris
- is an adjustable
diaphragm around a
central aperture
- the pupil, which
controls the amount of
light entering the eye
- The concentration of
melanocytes is the main
factor determining the
hue of the iris.
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16. Muscles of the Iris
1. Sphincter Pupillae
- This is a flat annulus of smooth
muscle about 0.75 mm wide and
0.15 mm thick.
- Its densely packed fusiform
myocytes are often arranged in
small bundles, as in the ciliary
muscle, and pass
circumferentially around the
pupil.
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17. Muscles of the Iris
2. Dilator Pupillae
- A thin stratum lying
immediately anterior to the
epithelium of the posterior iridial
surface,
- its fibers are in fact the
muscular processes of the
anterior layer of this epithelium,
- their apical processes form the
epithelium itself.
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18. Retina
The Neural Coat
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19. The Retina
- is the neural, sensory stratum of the eyeball
- It is thin, being thickest near the optic disc
- contains a variety of cell types. They include the
photoreceptors (rod and cone cells),
- Near the centre of the retina is an oval, yellowish area, the
macula lutea which has a central depression, the fovea
centralis, where visual resolution is highest.
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20. Optic Disc
- This region, where retinal
tissues meet the neural
elements of the optic nerve
- Besides being the exit
point for the optic nerve
fibres, it also provides a
point of entry and exit for
the retinal circulation.
- superomedial to the
posterior pole of the eye
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21. Rods and Cones
Cone cells
- chiefly responsible for high spatial resolution and colour
vision in good lighting conditions (photopic vision),
- highly concentrated at the fovea centralis, but they
populate the whole retina, intermingled with rods
Three types according to their maximum spectral sensitivities:
red, green and blue
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22. Rods and Cones
Rods
- provide high monochromatic sensitivity to a much wider
range of illumination down to much lower intensities
(scotopic vision) although with relatively low spatial
discrimination because of their different neural connections.
- Rods are excluded from the fovea.
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23. The Refractive of the eye which
The components Media
transmit and refract light
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24. Composed of:
1. Cornea,
2. Acqueous humor,
3. Lens,
4. Vitreous humor.
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25. Aqueous Humour
- The total quantity of aqueous humour is small, filling the
anterior and posterior chambers.
- The ciliary processes are responsible for its production
- is an avenue for nutrients, and metabolic exchange for the
avascular tissues of the cornea and lens.
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26. Vitreous Body
- fills the vitreous chamber, occupying about four-fifths of the
eyeball.
- It is colourless, consisting of approximately 99% water, and
although apparently structureless, a sparse but organized
cellular and fibrous content is present.
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27. Lens
- is a transparent, encapsulated,
biconvex body, placed between
the iris and the vitreous body.
- encircled by the ciliary processes,
to which it is attached by the
zonular fibres collectively forming
the zonule holding the lens in
place and transmitting the forces
stretching the lens except in
visual accommodation.
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28. CONDITIONS OF THE EYE
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29. Emmetropia
• Ideal state of the eye in
which no refractive
error is present
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30. Myopia
• Also known as
nearsightedness, is a
condition in which a person
can see near objects more
clearly than distant objects.
• Light focusses in front of the
retina
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31. Hyperopia
• Also known as
farsightedness, is a
condition in which a person
can see distant objects more
clearly than near objects.
• light focusses behind the
retina
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32. Presbyopia
• Normal part of aging.
• It develops as the lens of the eye becomes less flexible and
loses its ability to focus on near objects.
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33. Lens become thicker when viewing near objects
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34. The lens in the presbyopic eye cannot change shape to
focus on near objects
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35. Astigmatism
• A condition in which objects, both near and
far, appear blurred.
• Often occurs in combination with myopia nad
hyperopia.
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36. Cataract
• Is a cloudiness or
opacificationin the
normally clear and
transparent lens of the
eye.
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37. THE ACCESSORY STRUCTURES
OF THE EYE
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38. • 1. The Eyelids
• 2. The Lacrimal Apparatus
• 3. The Eye Muscles
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39. Functions:
1. provide protection,
2. lubrication, and
3. support
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40. The Eyelids
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41. - 2 movable folds, with the upper being more larger and
movable, due to the presence of the levator palpebra
superioris.
- covered by skin, externally, and mucous membrane (palpebral
conjunctiva) in the deep aspect.
Functions :
1. provide protection when firmly closed
2. keep the surface of the eyeball lubricated with its continual
blinking.
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42. Layers of the Eyelid
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43. Layers of the Eyelid
1. Skin
2. Loose subcutaneous tissue
3. Muscular layer
4. Submuscular layer
5. Tarsal plates
6. Conjunctiva
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44. 1. Skin
- eyelashes
- sebaceous glands (glands of Zeis)
Sty - infection of the glands of Zeis
- sweat glands (glands of Moll)
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45. 2. Loose subcutaneous tissue
- extremely loose and easily
distended by blood and
fluid
3. Muscular layer
- orbicularis oculi muscle
4. Submuscular layer
- contains sensory nerves
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46. 5. Tarsal plates
- 2 thin plates of dense connective tissue
- forms and supports the eyelid
- presence of lateral and medial tarsal ligaments
- receives the levator palpebra superioris
6. Conjunctiva
- mucous membrane that attaches the eyeball to
the eyelid ( palpebral and bulbar)
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47. STRUCTURES PRESENT IN THE EYELIDS
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48. 1. Palpebral fissure
2. Palpebral commissures (canthi)
a. lateral - more acute, placed
directly against the globe
b. medial - lacrimal lake, lacrimal
caruncle, lacrimal papilla, lacrimal
punctum
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49. The Lacrimal Apparatus
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50. Composed of the following
structures:
1. lacrimal gland, which
secretes a complex fluid
(tears) and whose excretory
ducts convey fluid to the
surface of the eye,
2. the paired lacrimal
canaliculi,
3. the lacrimal sac and
4. the nasolacrimal duct, by
which the fluid is collected
and conveyed into the nasal
cavity.
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51. 1. Lacrimal Gland
- located superolaterally
along the orbit
- secretion empties in
the pocket between
the eyeball and the
eyelid
- secretes tears which are
alkalinic, watery, and
contain lysozyme
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52. 2. Lacrimal Canaliculi
- superior and
inferior
- conducts the
tears to the
lacrimal sac
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53. 3. Lacrimal Sac
- located in the
lacrimal fossa
- presents a fundus
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54. 4. Nasolacrimal Duct
- 3/4 of an inch in
length
- drains into the
inferior nasal
meatus
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55. The Orbit
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56. The Orbit
- contains the eyeball in its
anterior part and the
posterior part is filled
with fat, fascia, muscles,
blood vessels and nerves
- Capsule of Tenon
separates the anterior
and posterior
- Periorbita lines the orbit
and is continuous with
the dura mater of the
brain
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57. The Eye Muscles
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58. The Eye Muscles
- Composed of the 7 muscles of the eye
- Lateral rectus is supplied by the Abducent N.
- Superior oblique is supplied by the Trochlear N.
- The rest is supplied by the Oculomotor N.
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