Anatomy and Physiology of vision I

Question 1

What are the main functions of the eye?

Answer 1

To transmit light to the retina
To refract light so that it is focused on the retina
To transduce light into an electrical signal
To process the electrical signal before it is transmitted to the CNS

Question 2

What are the two eye segments? What are they composed of?

Answer 2

Anterior segment (Anterior and posterior chambers)
Posterior Segment (vitreous, retina, choroid and optic nerve)

Question 3

What is the part of sclera covering the optic nerve?

Answer 3

Lamina cribosa

Question 4

What are the 3 components of the conjunctiva ?

Answer 4

Palpebral
Forniceal
Bulbar

Question 5

What is episclera and what are its two layers?

Answer 5

Vascular plexus between the conjunctiva and the sclera

Superficial episcleral vessels
Deep episcleral vessels

Question 6

What are the relative refractive powers of the cornea and the lens?

Answer 6

Cornea: 2/3 refractive power (fixed)

Lens ~1/3 refractive power (variable)

Question 7

Why is the cornea transparent?

Answer 7

A-vascularity
Unifrom structure
Deturgescence

Question 8

what are the 5 layers of the cornea?

Answer 8

Epithelium, bowman’s membrane, stroma, Descemet’s membrane, endothelium

Question 9

What is the function of corneal epithelium?

Answer 9

Acts as a barrier to trauma and infection (5-8 cells thickness)

Question 10

What are two important characteristics of the stroma?

Answer 10

1- comprises 90% of the corneal thickness

2- does not regenerate

Question 11

What is the function of the endothelium?

Answer 11

maintains corneal hydration

Question 12

What is the structural difference between the sclera and the cornea?

Answer 12

Same structure, but the collagen in the sclera is coarse and irregularly distributed

Question 13

What are the components of a lens?

Answer 13

capsule, cortex, nucleus, epithelium

Question 14

What are the major classes of cataracts?

Answer 14

Cortical
Nuclear sclerosis (aging)
Posterior subcapsular (Steroids, diabetes)

Question 15

Where can the intra ocular lens be inserted?

Answer 15

Posterior chamber (inside the capsule)
Anterior chamber

Question 16

What are the components of the Uvea?

Answer 16

Iris
Cilliary body
Choroid

Question 17

What is the significance of the stroma in the iris?

Answer 17

Contains the following:
1- Muscles: a) shincter constricting muscles (CNIII) b) dialator muscles
2- Melanocytes
3- Blood vessels

Question 18

What is a common finding associated with congenital horner’s syndrome?

Answer 18

Heterochromia

Question 19

What are the main parts of the ciliary body?

Answer 19

Pars plicata

Pars plana

Question 20

What are the functions of the ciliary body?

Answer 20

1- Production of aqueous humour

2- Accomodation

Question 21

Where is the aqueous humour produced?

Answer 21

Produced by the two layered epithelium in the ciliary body to nourish avascular structures (cornea and lens)

Question 22

How is the aqueous humour drained from the anterior chamber?

Answer 22

Drained by tubercular meshwork to canal of schlem and via uveascleral outflow to episcleral venous vessels

Question 23

What two structures form the angle?

Answer 23

The cornea and the iris

Question 24

What causes glaucoma?

Answer 24

Obstruction of the aqueous drainage which leads to increased intraocular pressure (IOP)

Question 25

What effect does increased IOP have on the optic nerve?

Answer 25

Could result in glaucomatous damage to the optic nerve | Appears as a reduced rim in fundoscopy

Question 26

How is glaucomatous increased IOP treated?

Answer 26

Either by decreasing aqueous production by the ciliary body or by increasing aqueous outflow through the trabecular meshwork and uveouscleral outflow pathways

Question 27

What is the accommodation process for near sight? (near Triad)

Answer 27

1- Ciliary body contracts and moves anteriorly which leads to relaxation of the zonules which allows the lens to round up in shape 2- Convergence of the eyes 3- Pupillary constriction to decrease spherical aberration

Question 28

What makes up the vitreous?

Answer 28

99% water, 1% collagen, HCL

Question 29

What changes to the vitreous occur with age?

Answer 29

The vitreous liquifies and condenses

Question 30

What is the centre of the retina? What is the centre of that centre? (yes for real)

Answer 30

Macula and fovea

Question 31

What constitutes the retinal blood barrier? What is its function?

Answer 31

The retinal pigment epithelium (RPE) that supports the metabolism of photoreceptors

Question 32

What is the function of the choroid?

Answer 32

Highly vascular part of the Uvea that provides the retina with much of its metabolic requirements

Question 33

What makes the choroid essential to the fovea?

Answer 33

The fovea is avascular and its support is dependent on the choroid

Question 34

What is the pathway of the optic nerve?

Answer 34

Intraocular (1mm), intraorbital (25mm), intracannalicular (9mm), intracraneal (16 mm)

Question 35

What constitute the adnexal structures?

Answer 35

Bony orbits, lacrimal ducts, eyelids, and extraocular muscles

Question 36

What makes up the roof of the orbit?

Answer 36

Frontal bone and lesser wing of the sphenoid

Question 37

What makes up the floor of the orbit?

Answer 37

Zygomatic bone, maxillary bone, palantine bone

Question 38

What makes up the medial wall of the orbit?

Answer 38

Ethmoid bone, maxillary bone, lacrimal,` and sphenoid

Question 39

What makes up the lateral wall of the orbit?

Answer 39

Greater wing of the sphenoid, and zygomatic bone

Question 40

What is the first bone to break following an orbital trauma (ex punch to the eye)?

Answer 40

Floor (weakest)

Question 41

What passes through optic foramen?

Answer 41

Optic nerve and artery (through sphenoid bone)

Question 42

What passes through SOF?

Answer 42

CNIII, IV, V1, VI, and vessels (between greater and lesser wings of sphenoid)

Question 43

What passes through IOF?

Answer 43

Sympathetics and vessels

Question 44

What muscles originate at the orbital apex?

Answer 44

All but Inferior oblique

Question 45

What muscles are responsible for lid opening?

Answer 45

Levator palpebrae superioris (CNIII) and Mullers muscles (Sympathetics )

Question 46

What muscles are responsible for lid closing?

Answer 46

Obircularis oculi (CNVII)

Question 47

What is contained within the eyelid?

Answer 47

Muscles, glands, tarsal plate, site of attachment of orbital plate

Question 48

What is the tear film composed of?

Answer 48

1- Mucin layer 2- Aqueous layer 3- Lipid layer

Question 49

Where is the mucin layer produced and what is its function?

Answer 49

Produced by conjunctival goblet cells | Aids tear adherence to the cornea

Question 50

Where is the aqueous layer produced and what is its function?

Answer 50

Produced by the accessory lacrimal glands (glands of Krau and Wolfring) Forms bulk of tear film

Question 51

Where is the lipid layer produced and what is its function?

Answer 51

Produced by meibomian gland in lid margin | Reduced tear evaporation

Question 52

What is the function of the tear film?

Answer 52

Maintains refractive function | Nourishes cornea

Question 53

What could cause dry eye?

Answer 53

Loss of lipid layer (tear evaporation) loss of aqueous layer, loss of mucin layer (tear slides off)

Question 54

Where is the lacrimal gland located?

Answer 54

Lateral superior orbit

Question 55

What causes the lacrimal gland to secrete?

Answer 55

In reflex to bright light, emotion, and irritation (CN II, V)

Question 56

What glands provide basal secretions? Where are the located?

Answer 56

Kraus and Wolfring | Located in conjunctival fornix

Question 57

How are tears drained? List the components of the pathway

Answer 57

Punctum, canaliculi, lacrimal sac, naso-lacrimal duct (valve of Hasner under inferior concha)