Biology 489- Vision Class

The ancient Egyptians made use of urine to treat what condition?

Mist before the eye. Probably bacterial conjunctivitis

What Greek scientist explained that vision occurred when objects shed their atoms into space?

Democritus

Who was the first to describe the ray theory of light?

Empedocles

Who described the visual ray theory using geometry?

Euclid

Who was the greatest Islamic investigator of the eye?

Alhazen

Who respected Greek thought, defended Euclid’s visual ray theory, and tried to prove it with optics?

Al-Kindi

Who was the first scientist to explain the process of vision by refraction within the eye?

Kepler

Who was the first scientist to demonstrate Huygens wave theory of light using a double-slit interference experiment?

Young

This German physician and professor of physics developed the ophthalmoscope for clinical applications:

Von Helmholtz

Who said “It has not yet been 20 years since there was discovered the art of making eyeglasses”, thereby placing the invention of spectacles around 1285?

Da Rivalto

Who patented the first meniscus lens in 1804?

Wollaston

What year do we associate with the invention of the first contact lens?

1888

In 1947, the first all-plastic corneal lens was developed by which contact lens pioneer?

Touhy

Who performed the first documented cataract procedure in 750 BCE?

Susruta

What procedure was used by medieval physicians to remove cataracts?

Couching

What are the three layers of the eye and their contents?

• Outer fibrous – Connective tissue, Cornea, Sclera

• Middle vascular – Uvea (Iris, Ciliary body, Choroid)

• Inner neural – Retina

List the three spaces (chambers) in the globe

Anterior, posterior, vitreous

Differentiate fossa, fissure, and foramen

• Fossa - Hollow depressed area

• Fissure - Narrow opening

• Foramen - Opening, perforation, orifice

Cranial bones provide what function?

Enclose and protect brain, eyes, and ears

What are the joints between cranial bones called?

Sutures

List the orbital contents

• The globes

• The EOM’s

• Orbital nerves

• Blood vessels

• Connective tissue

Name the seven orbital bones

1.Frontal

2.Zygomatic

3. Maxilla

4.Lacrimal

5.Ethmoid

6.Sphenoid

7.Palatine

Which bones are common to both orbits?

Frontal, Sphenoid, Ethmoid

A blow-out fracture typically affects which orbital bone?

Maxilla

List the paranasal sinuses

Sphenoidal, Ethmoidal, Maxillary, Frontal

The periorbita acts as an attachment site for which structures?

Muscles, Tendons, Ligaments

What is a circular dense connective tissue sheet that helps to prevent facial infections from entering the orbit?

Orbital septum

Describe Tenon’s capsule

• Dense connective tissue that encases the globe

• Lies between the conjunctiva and the episclera

• Acts as barrier to prevent the spread of orbital infections into the globe

What are the three eyebrow muscles and their associated functions?

• Frontalis – Surprise

• Procerus – Aggression

• Corrugator – Concentration

When you hear, or see, the term “palpebrae”, which ocular structure do we automatically think of?

eyelid

List the four functions of the eyelids

1. Cover the globe for protection

2. Contain structures that produce tears

3. On opening, they spread tears over the anterior surface of the eye

4. On closure, they move tears to drainage areas near medial canthus

Where can you find the lateral canthus and the medial canthus?

Palpebral fissure

What do we call a highly vascularized, crescent-shaped fold of conjunctiva?

Plica semilunaris

Name the structures found in the caruncle

• Accessory lacrimal glands

• Fine hairs

• Sebaceous and sweat glands

List four facts about the cilia (lashes)

• Arranged at lid margin in double or triple rows

• ~150 upper / ~75 lower

• Replacement lashes grow to full size in 10 weeks

• Each lash is replaced every 5 months

What is the main function of the orbicularis oculi muscle, and which cranial nerve provides innervation for this function?

• Closes the eyelid

• CN VII

Name three things that can make you blink involuntarily

• Loud noise

• Corneal, conjunctival, or ciliary touch

• Sudden approach of object

What is the main function of the levator muscle, and which cranial nerve provides innervation for this function?

• Opens the eyelid

• CN III

The tarsal muscle of Müller is what type of muscle tissue?

• Smooth

• Involuntary

Meibomian glands are embedded in which structure?

Tarsal plate

What structure is the thinnest skin in the body, covers the front of the lid, and ends at the mucocutaneous junction of the lid margin?

Lid epidermis

Name the thin translucent membrane that begins at the mucocutaneous junction.

Conjunctiva

Name the two tear production structures found in the conjunctiva

• Goblet cells

• Accessory lacrimal glands (Krause, Wolfring)

List the functions of the tear film:

• Keeps surface of eye moist and lubricates the area between globe and eyelids

• Traps debris and removes old cells

• Primary source of atmospheric oxygen for the cornea

• Smooth refractive surface for best optical function

• Contains antibacterial substances to prevent infection:

o Lysozyme

o β-Lysine

o Lactoferrin

o Immunoglobulins

• Keeps cornea hydrated through change in tonicity

• Contains growth factors and peptides to regulate ocular surface wound repair

Name the three tear layers and the structures that secrete them

• Mucin – Goblet cells

• Aqueous – Main lacrimal gland, accessory lacrimal glands

• Lipid – Meibomian glands

Name the structures of the lacrimal secretory system

• Main lacrimal gland

• Acc. Lacrimal glands

• Meibomian glands

• Goblet cells

• Zeis glands

Describe the route that a single aqueous tear takes starting in the main lacrimal gland and ending in a Kleenex tissue

• Main lacrimal gland

• Eye

• Lacrimal lake

• Puncta

• Canaliculi

• Nasolacrimal sac

• Nasolacrimal duct

• Tissue

List the six types of eye movements that a normal human eye is capable of…

1. Adduction

2. Elevation

3. Intorsion

4. Extortion

5. Depression

6. Abduction

List the six EOM’s

1. SUPERIOR RECTUS

2. INFERIOR RECTUS

3. MEDIAL RECTUS

4. LATERAL RECTUS

5. SUPERIOR OBLIQUE

6. INFERIOR OBLIQUE

Five of the six EOM’s are attached to an annular cartilaginous tissue located in the posterior orbit. Name this structure.

Common tendinous ring

List the four requirements needed to satisfy the definition of “Primary Position of Gaze.”

1. Head erect

2. Eye located in sagittal plane

3. Eye located in horizontal plane lined up with centers of rotation of both eyes

4. Viewing optical infinity

Create a table of the six EOM’s, their origin, insertion, and primary action:

What is considered the principal refracting component of the eye?

Cornea

From external to internal, list the five layers of the cornea.

1. Epithelium

2. Bowman’s layer

3. Stroma

4. Descemet’s membrane

5. Endothelium

Describe the surface cells of the corneal epithelium

Approximately 2 layers of non-keratinized squamous cells

In which layer of the corneal epithelium do we find the wing cells?

Middle

The basal layer is the most internal layer of the corneal epithelium. This single layer of cells is responsible for producing what substance?

Basement membrane

Bowman’s layer consists of dense collagen fibrils randomly arranged in a ground substance. Where is this layer produced? Can it regenerate?

Epithelium and No

What type of cells produce collagen fibrils in the corneal stroma? What fact about the collagen fibrils accounts for corneal transparency?

1. Keratocytes

2. Regular spacing of the fibrils accounts for the cornea’s transparency

Can Descemet’s membrane regenerate?

Yes

Disruption of the corneal endothelium leads to these two conditions.

• Pleomorphism: Change in cell shape

• Polymegathism: Change in cell size

What two factors affect the cornea’s ability to function properly?

1. Refraction of light

2. Transmission of light

What three factors are needed for corneal light transmission?

• Smooth optical surface created by epithelium and tear film

• Absence of blood vessels

• Correct spatial arrangement of collagen fibrils

What structures restrict fluid from the tear film into the corneal epithelium?

Zonular junctions

Name the endothelial pump that is important to maintain proper hydration.

Na+/K+ ATPase pump

What physiological activity occurs in the corneal stroma when it swells?

Pumps remove excess fluid to maintain homeostasis

During corneal wound healing, which two corneal layers are neither regenerated nor replaced?

• Bowman’s layer

• Endothelium

Name three ways in which the cornea receives O2

• Diffusion of O2 from aqueous humor in the anterior chamber

• Conjunctival and episcleral capillary networks located in the limbus

• Atmospheric O2 through the tear film

What are the 5 structures responsible for corneal innervation?

• Cranial nerve V

• Ophthalmic division

• Nasociliary nerve

• Long and short ciliary nerves

• Corneal plexus

How is the sclera associated with the EOM’s?

The sclera provides attachment for the EOM’s

What type of tissue is episclera?

Loose vascularized connective tissue

What fact contributes to the sclera’s strength and flexibility?

Random arrangement and interweaving of collagen fibrils

The scleral spur is used as a reference point for which clinical procedure?

Gonioscopy, which helps to diagnose glaucoma

What structure can be found in the anterior scleral foramen?

Cornea

What two structures are found in the posterior scleral foramen?

• Optic nerve

• Lamina cribrosa

These vessels are found in the middle canals of the sclera

Vortex veins

Where is the limbus located?

Corneoscleral junction

What characteristic allows the ciliary body to change the shape of the lens?

Lenticular malleability

The change in dioptric lens power is known as what?

Accommodation

What is the transparent envelope that surrounds the lens?

Lens capsule

What structures attach the ciliary processes to the lens capsule?

Zonules

In the lens, what do we call the area responsible for cell mitosis?

Germinal zone

What lens structure is created from the epithelium when an elongated cell loses all of its organelles?

Lens fiber

What protein structures are found in high concentrations in the lens fiber cytoplasm?

Crystallins

Where do the Zonules of Zinn attach to the lens capsule?

At the pre and post equatorial regions

Describe the accommodative process when a far distant object is being viewed

• The ciliary muscle is relaxed, and located in a more posterior position

• The zonules are tight, and pulling on the crystalline lens

• The lens is less convex

Describe the accommodative process when a near object is being viewed

• The ciliary muscle is constricted, and located in a more anterior position

• The zonules are loose, and decrease their tension on the crystalline lens

• The lens is more convex

List four facts about the antioxidant glutathione

• High concentration in lens tissue

• Detoxifies free radicals in the young lens

• With age, glutathione movement into lens nucleus slows down

• Can create nuclear sclerosis (Cataract)

What three structures make up the filtration apparatus of the anterior chamber?

•Scleral spur

• Trabecular meshwork

• Schlemm’s canal

Name the outer region of the trabecular meshwork

Corneoscleral meshwork

Name the inner region of the trabecular meshwork

Uveal meshwork

What structure is a circular venous vessel containing aqueous humor, not blood?

Canal of Schlemm

List the four structures that bound the posterior chamber

1. Anterior vitreous

2. Equatorial zone of lens

3. Ciliary body

4. Posterior iris

What structure is responsible for aqueous humor production?

Epithelium of the ciliary pars plicata

List the structures involved when aqueous humor exits the anterior chamber

• Trabecular meshwork

i. Uveal meshwork

ii. Corneoscleral meshwork

• Canal of Schlemm

• Deep scleral plexus of veins

• Episcleral and conjunctival veins

What is the vitreous body composed of?

• 99% water

• Collagen

• Hyaluronic acid

• Hyalocytes

To what structures do we find the vitreous attached?

• Vitreous base

• Posterior lens

• Optic disc

• Macula

• Retinal vessels

Name the three vitreous zones

• Vitreous cortex

• Intermediate zone

• Cloquet’s canal

List four facts concerning the physiology of the vitreous

1. Stores metabolites for retina and posterior lens

2. Provides vehicle for movement of substances

3. “shock absorber” protecting retinal tissue during rapid changes in movement

4. Low concentration of particles allows transmission and refraction of light

Corneal Transplant Video Questions

Capybara!