Exam 1 - 001 Overview of the Eye

Question 1

What are the dimensions of the eye?

Answer 1

o Vertical: ~23 mm (superior to inferior)
o Horizontal: ~23.5 mm (Nasal to temporal)
o Antero-posterior diameter: ~24 mm
o Anterior sphere radius (cornea sphere): 7.8 mm
o Posterior sphere radius (whole eye): 11.5 mm

Question 2

Limbus

Answer 2

 Junction where the cornea and sclera are continuous with each other

Question 3

Anterior Pole

Answer 3

 found at the center of curvature of the cornea

Question 4

Posterior pole

Answer 4

 center of the posterior curvature of the eyeball

Question 5

Optic Axis

Answer 5

 line connecting the anterior and posterior poles

Question 6

Visual axis

Answer 6

 line passing through the fovea (NOT the same as the optic axis)

Question 7

Equator of the eyeball

Answer 7

 lies midway between the anterior and posterior pole of the eye
 located about 12 mm from the anterior pole
 vertical circle

Question 8

Optic Disc

Answer 8

 the anterior surface of the optic nerve that is visible during direct ophthalmoscopy

Question 9

Optic nerve

Answer 9

 formed by the axons of the ganglion cells in the retina

 exits the back of the eye slightly nasal to the posterior pole of the eyeball

Question 10

Lamina cribrosa

Answer 10

 the part of the sclera the ganglion cell axons pass through to exit the eyeball
 This region of the sclera is full of “holes” and the ganglion cell axons exit the eyeball through these holes

Question 11

Zonules

Answer 11

 thin connective tissue strands that extend from the pars plana of the ciliary body (near the ora serrata) to the lens capsule
 composed of a glycoprotein arranged as microfibrils (that are related to but not the same as typical elastic fibers

Question 12

Lens

Answer 12

 biconcave disk located posterior to the iris and anterior to the vitreous
 enclosed within a capsule
 focuses light onto the retina

Question 13

Vitreous

Answer 13

 clear, gelatinous material that fills the space between the lens and the retina and has the consistency of raw egg whites

Question 14

Functions of the Vitreous

Answer 14

• transmit light
• hold the retina in the proper position in relation to the choroid
• act as a shock absorber to protect the retina during quick eye movements and physical activities
• acts as a reservoir of metabolites for the retina and lens

Question 15

Hyaloid membrane

Answer 15

 encloses the vitreous body

 a condensation of collagen fibrils at the outer edge of the vitreous

Question 16

Fovea

Answer 16

 specialized region of the retina where a person has the highest visual acuity
 lies in the temporal retina
 formed by the peripheral displacement of the inner retinal layers, while leaving the outer, photoreceptive layers of the retina
 Serves to allow incoming light to have greater, more direct access to the photoreceptors than elsewhere
 The fovea contains the outer layers of the retina

Question 17

Ora serrata

Answer 17

 anterior termination of the retina

 forms as the retina thins until it ends and the ciliary body begins

Question 18

Anterior Chamber

Answer 18

 Connected to the posterior chamber by the pupil

 The small space lying behind the cornea that contains the aqueous humor (about 0.2 mL)

Question 19

Boundaries of the Anterior Chamber

Answer 19

• Anterior – posterior surface of the cornea
• Peripheral – trabecular meshwork and anterior surface of ciliary body
• Posterior – iris and anterior surface of the lens that lies by the pupil

Question 20

Posterior Chamber

Answer 20

 Connected to the anterior chamber via the pupil
 Slit-like space lying behind the iris
 Zonules pass through to attach to the lens capsule
 Filled with aqueous humor (volume is about 0.06 mL)

Question 21

Boundaries of the posterior chamber

Answer 21

• Anterior: posterior surface of the iris
• Lateral/peripheral: pars plicata of ciliary body
• Medial: equatorial zone of the lens
• Posterior: anterior surface of the vitreous (anterior hyaloid membrane)

Question 22

Cornea

Answer 22

 part of the outer layer of the eye
 clear fibrous layer
 forms the anterior 1/6 of the eye

Question 23

Sclera

Answer 23

 part of the outer layer of the eye
 opaque white fibrous layer
 composed of collagen
 covers 5/6 of the eyeball

Question 24

Iris

Answer 24

 part of uveal layer (middle layer)
 sheet like circular diaphragm anterior to the lens
 has a central hole called pupil
 Sphincter and dilator pupillae muscle of the iris regulates the pupil size

Question 25

Ciliary Body

Answer 25

-part of uveal layer (middle layer)
-posterior to the iris
-continuous anteriorly with the iris and posteriorly with the choroid
-extends from the iris to the anterior edge of the retina
-The posterior border of the ciliary body is approximately at the point of insertion of the rectus muscles into the sclera
-The anterior termination of the ciliary body is approximately located at the limbus of the eye
-Contains smooth muscle (ciliary body muscle)
•Allows for accommodation
-Wider laterally (~6.9 mm) than medially (~5.5 mm)

Question 26

Parts of the ciliary body

Answer 26

• Pars plicata – anterior folded region (ciliary processes)

* Pars plana – posterior, flat region

Question 27

Choroid

Answer 27

 part of uveal layer (middle layer)
 lies adjacent to the retina (directly external)
•helps to supply nutrients to the outer layer of the retina
 posterior to ciliary body
 extends from the ciliary body anteriorly to the optic nerve posteriorly
 Contains many blood vessels and a capillary bed
 Highly vascularized and pigmented

Question 28

Retina

Answer 28

 innermost layer
 thin (0.1-0.5 mm
 transparent
 photosensitive
 layer of neural tissue
 Function
• Transforms light stimuli into nerve impulse to form an image in the brain
 Extends from the ciliary body (anteriorly) to the optic nerve (posteriorly)
 Lies directly internal to the choroid
 Composed of layers
• Retinal pigmented epithelium (RPE)
o Outer pigmented layer is a single layer that lies adjacent to the choroid
• 9 inner sensory layers
o Lie closer to the vitreous
o These are the layers to detach during a retinal detachment
• Hisologically composed of alternating pink and blue bands
o Blue layers – contain the nuclei of various cells
o Pink layers – synaptic areas between denrites and axons of cells in adjacent layers

Question 29

Bulbar Conjunctiva

Answer 29

 externally the anterior part of the sclera covering
 transparent layer
 begins at the limbus
 at the fornix it is reflected onto the posterior surface of the eyelid as the palpebral conjunctiva

Question 30

Fornix

Answer 30

 region where the palpebral conj and bulbar conj meet

Question 31

Palpebral Conjunctiva

Answer 31

 Transparent layer lying on the posterior part of the eyelid

Question 32

Anterior Segment

Answer 32

o Anterior Segment

 Portion of the eyeball between the cornea and the posterior surface of the lens

Question 33

Contents of the anterior segment

Answer 33

• Cornea
• Iris
• Ciliary Body
• Lens and its zonules
• Anterior and posterior chambers

Question 34

Posterior Segment

Answer 34

 Portion of the eyeball posterior to the lens

Question 35

Contents of the posterior segment

Answer 35

• Retina
• Choroid
• Optic nerve
• Vitreous

Question 36

Three layers of the eyeball

Answer 36

Outer layer
Uveal Layer (Middle)
Inner Layer

Question 37

What is the outer layer of the eyeball?

Answer 37

Sclera and cornea

Question 38

What is the uveal layer of the eyeball?

Answer 38

Iris
Choroid
CIliary body
Contains blood vessels
Highly pigmented due to melanocytes that are present in ALL three layers
Also have pigment granules that are in epithelial cells and ciliary body

Question 39

What is the inner layer of the eyeball

Answer 39

The retina

Question 40

Position of the ciliary body

Answer 40

Circular and wraps around the iris

Question 41

What structures of the eye form an annulus?

Answer 41

Annulus=ring
Ciliary Body
Iris
Limbus