Ocular A+P Lids, Lashes, Conjunctiva, EOMs, Cornea, Uvea, Lens

What structures make up the fibrous tunic of the eye?
What structures make up the vascular tunic of the eye?

What structures make up the neural tunic of the eye?

Fibrous - Cornea and sclera

Vascular - Iris, CB, and choroid

Neural - retina

What type of cells make up the corneal epithelium?

a. Stratified squamous

b. Columnar

A

The corneal endothelium facilitates nutrient flow from what to what? It facilitates oxygen flow from what to what?

Nutrient: Anterior chamber to cornea

Oxygen: Cornea to AC

What are the layers of the corneal epithelium?

Anterior Epithelium

Bowman’s

Corneal stroma

Descemet’s

Endothelium

What is osteogenesis imperfecta?

Blueish sclera due to thinning of the sclera

What structures make up the anterior uvea?

Iris and CB

What are 2 common problems of the eyelashes?

Blepharitis and mites

What 3 muscles are responsble for eyelid elevation?

Levator palpebrae superioris, Muellers, and Frontalis

List the innervation, origin, and insertion of the levator.

CN III

Origin: Sphenoid Bone

Insertion: Superior Tarsal Plate

List the innervation, origin, and insertion of Muellers

Sympathetic nervous system

Origin: Base of levator

Insertion: Superior tarsal plate

List the innervation, origin, and insertion of the frontalis muscle.

CN VII

Origin: Frontal bone

Insertion: Superior obital rim

What muscle is responsible for eyelid closing?

Orbicularis oculi

There is a palpebral and orbital portion of the orbicularis oculi. The palpebral portion contains what 2 types of muscles?

Muscle of Riolan and Horner’s Muscle

What is the role of the Muscle of Riolan?

Keep eyelid against globe and controls oil excretion of Meibomian glands

What muscle is responsible for frowning? What is innervated by? What is its origin?

Corrugator supercilii

Innervated by CN VII

Origin is frontal bone

What 3 CNs are responsible for reflex blinking?

CN II, V, VIII (2,5,8 - optic, trigeminal, auditory)

Which CN is responsible for the corneal and facial reflex? The dazzle, menace, and glare reflex? The auditory reflex?

Corneal facial - CN V

Dazzle menace glare - CN II

Auditory - CN VIII

What is the corneal reflex latency in ms?

160 ms

What type of tumor results in a loss of the corneal reflex?

Cerebellar pontine tumor

Myerson’s sign is when patient’s with parkinson’s disease cannot withhold a reflex when something touches the skin near the eye. What type of reflex are we talking about?

Facial reflex

What is a dazzle reflex? Glare reflex? Menace reflex?

Dazzle - bright light

Glare - light shining off something

Menace - approaching foreign object

In unconscious blnking, what is the total blink duration in ms?

250 ms

What divisions of the trigeminal nerve provided sensory innervation to the eyelids? 

Ophthlamic V1 and Maxillary V2

The sensory innervation of the upper eyelid was supplied by what branches of the ophthalmic nerve?

Supratrochlear, Supraorbital, and Lacrimal

The sensory innervation of the lower eyelid was supplied by what branches of the maxillary nerve?

Infratrochlear, infraorbital, and zygomatico facial nerve

The medial artery branches off of what artery? The lateral artery branches off of what artery?

Medial - ophthalmic

Lateral - lacrimal

What is the pathway of the medial palpebral arteries? What is the pathway for the lateral palpebral arteries?

Medial: ICA —> Ophthalmic —> Medial palpebral

Lateral: ICA —> Ophthalmic —> Lacrimal —> Lateral palpebral

What are the normal dimensions of the palpebral fissure length and width?

Length: 27-30mm

Width: 10-12mm

What is a common cause of increased fissure width?

Thyroid associated orbitopathy

What is a bitot spot? What are 2 common causes?

Dry spot on the conjunctiva

Causes: pinguecula and pterygium

What are 2 accessory oil glands?

Glands of Zeiss and Moll

What are 2 accessory aqueous glands?

Glands of Kraus and Wolfring

What are the 3 most common microorganisms found near the eyelids? List them from most common to least.

Staph epidermidis > Staph aureus > Demodex

An external hordeolum is an inflammation of what? What about internal hordeolum?

External: inflammation of Zeiss and Moll

Internal: inflammation/blockage of Meibomian

What eyelid condition is described as bilateral inflammation of the lid margins and is common for kids and older individuals?

Marginal blepharitis

What eyelid condition is described as bilateral inflammation of the meibomian glands and is chronic and painful

Meibomitis

What anatomical deformity of the eyelid is described as a loss of skin elasticity with age?

Dermatochalasis

Which anatomical deformation of the lid is described as a result of repeated edema of the lid tissue resulting in very thin skin

Blepharochalasis

Congenital ptosis is due to the developmental failure of what?

LPS

What type of conjunctivitis results from an allergic reaction to pollen, pollution, and CLs?

Giant papillary conjunctivitis

What are 4 components in the tear film that aids in protection?

Lysozymes, beta-lysin, secretory IgA, and Mucin

What are the 4 layers of the tear film?

Lipid, aqueous, mucin, glycocalyx

The lacrimal gland supplies what percentage of the aqueous layer? What about the accessory lacrimal gland?

95% ; 5%

Does the aqueous layer provide bacteriostatic or bacteriocidal protection?

Bacteriostatic from lysozymes, beta lysin, and lactoferrin

What type of vitamin deficiency leads to a decrease in goblet cells and therefore results in dry eye?

Vitamin A

What is the thickness of the tear film? What is the average tear volume?

7-8 uM ; 8 uL

What are 5 methods to assess aqueous production rate? Which is the most accurate?

1. Tear meniscus height (0.1-0.3 mm)

2. Schirmer tear strip (>10mm)

3. Coated threads

4. Sponge

5. Fluorophotometry

What are 4 drugs that decrease tear production?

HTN drugs, Antiulcers, Decongestants, and antihistamines

T/F Basal tears are from lacrimal and accessory lacrimal gland whereas stimulated tears are completely from lacrimal gland.

True

What are the neurotransmitters that are secreted in parasympathetic control of tears?

Acetylcholine and VIP

Which NT is released in sympathetic control of tear production? Which receptors increase tear production? Which ones decrease?

Norepinephrine

Increase: Alpha 1 receptors

Decrease: Beta adrenergic receptors

The acinus-intercalated duct region secretes _______ similar to plasma while the later ductal segments secrete ___ and___.

Acinus-intercalated: isotonic ultrafiltrate

Later ductal regions: K+ and Cl-

Detail how there is a production of isotonic ultrafiltrate from the acinar regions? (What are the ions involved and the overall ionic change in the cells).

At the base of the cell, there is a Na+/K+ active pump that pumps Na+ outside. This allows the Na/Cl cotransporter to transport those two ions into the cell. This results in an overall increase [Cl-] in the cell which leads to secretion of Cl- into the lumen. The increased negative charge in the lumen draws Na+ out and therefore results in water being pulled into the lumen, producing the isotonic ultrafiltrate of plasma.

What are 3 common protein in tears? Which protein controls osmolarity?

Albumin, globulin, and lysozymes

Rank the following from highest to lowest concentration for: unstimulated tears and stimulated tears

Unstimulated: albumin>globulin>lysozyme

Stimulated: globulin>lysozyme>albumin

What are the 4 general functions of tear proteins? (Hint: CARD)

1. Control infection

2. Act as pH buffer

3. Regulate osmolarity

4. Decrease surface tension

What are 3 methods of tear removal?

Drainage, evaporation, and absorption

What is the term used to describe the phenomenon in which tears flow from low temp areas (cornea) to areas of high temp (lid margins) and higher surfactant concentration?

Marangoni Flow

When we are awake, what percentage of our tears are eliminated through absorption and what percentage is eliminated with evaporation? What about when we are asleep?

Awake: 75% abs, 25% evap

Asleep: 100% abs

What are the 3 layers of connective tissue?

Epimysium, perimysium, and endomysium

What are unique characteristics about EOMs?

• Fast and precise

• Fatigue resistant

• More blood vessels and flow (2nd to cardiac)

• Resistant to injury and oxidative stress

What are en plaque motor nerve endings? En grappe motor nerve endings?

En plaque - large diameter with single nerve ending

En grappe - small with multiple nerve endings

Which muscle zones/bands get shorter with contraction? Whivh band does not change in length with contraction?

H zone and I band gets shorter

A band does not change

Which nervous system innervates Sherring’s Law?

CNS

What is the insertion point of the recti muscles called? List the muscles from closest to furthest from limbus.

Spiral of Tillaux - medial, inferior, lateral, superior

What is the origin of all the recti muscles?

Common Tendinous ring (annulus of Zinn)

What nerves are protected by the CTR?

CN II, CN III, CN V specifically nasociliary of ophthalmic VI, CN VI

What is the ligament that connects the sheaths of IO and IR?

Suspensory ligament of Lockwood

Which EOMs does the inferior division of the oculomotor nerve innervate?

MR, IR, IO

T/F All EOMs are supplied by ophthalmic artery and vein but LR is also supplied by infraorbital artery and IR is also supplied by lacrimal artery.

False - All EOMs are supplied by ophthalmic artery and vein but LR is also supplied by lacrimal artery and IR is also supplied by infraorbital artery.

1. Which is the thinnest and weakest of the 4 recti

2. Which is the widest, heaviest, and strongest EOM?

3. Which EOM is the longest and thinnest?

4. Which EOM is the shortest?

5. Which EOM is the shortest of the recti?

6. Which EOM is the longest of the recti?

1. LR

2. MR

3. SO

4. IO

5. IR

6. SR

What is the average axial length of the cornea?

24 mm

What is the central thickness range of the cornea?

500-700 uM

The cornea provides UV protection. How much UVC does it block? How about UVB? How about UVA?

UVC: 100%

UVB: 92%

UVA: Most blocked

Only 1% of UV light ever reaches the cornea

What are 4 mechanisms that the cornea has for UV protection?

1. High levels of Vit C

2. High levels of glutathione

3. Crystallins in cornea

4. Cellular repair system that reverse damage to DNA

What are the 3 layers of the corneal epithelium?

1. Strat epithelium

2. Wing cells

3. Basal cells

There are 6 components of the stratified epithelium that aids in barrier action. List the role of each component.

1. Tight junction

2. Adherens jxn

3. Desmosomes

4. Gap jxn

5. Actin linked cell matrix jxn

6. Hemidesmosomes

1. Deals hap between epi cells

2. Connects actin filament between cells

3. Connects intermediate filament between cells

4. Allows small water soluble molecules to pass between cells

5. Anchors actin filaments in cell to E

   CM

6. Anchors intermediate filaments in cell to ECM

Which layer of the epithelium is responsible for regeneration/mitosis and is a heavy anchor to hold onto the basement layer?

Basal cell layer

Which corneal layer is acellular, non regenerative and absorbs primarily UV-B?

Bowman’s Layer

Which layer of the cornea is also known as the substantia propria and gives strength to resist intraocular pressure?

Corneal stroma

What are 5 components of the stroma?

Collagen fibrils, keratocytes, ground substance, blood cells, and stromal stem cells

Which corneal layer can be regenerated when damaged and is more attached to the endothelium than to the stroma?

Descemet’s Membrane

Which of the two layers of Descemet;s (anterior or posterior lamina) is secreted by the endothelium throughout our lifetime and becomes thicker?

Posterior

Schwalbe’s line represents the termination of which layer of the cornea?

Descemet’s membrane

What is the average endothelial count in children? How about in 80 year olds?

Children: 2000-4000 cells/mm2
80 year olds: 1000-2000 cells/mm2

Hassal Henle bodies and guttata represent mounds of thickened Descemet’s that is bulging into the endothelium but HH bodies usually are seen in the (periphery/center) whereas guttata are found in the other. 

Periphery

Destructive interference in the cornea allows for clarity and occurs when there is a change in the index of refraction that occurs in a distance less than ___ the wavelength of visible light (400-700nm).

Less than ½ the wavelength

There are a total of 12 aquaporins in the cornea. Which ones are made to exclusively transport water? What about the ones that can transport both water and glycerol (these ones are called aquaglycoporins)?

Exclusively water; AQP 0,1,2,4,5

Water and glycoproteins: AQP 3,7,9,10

Ground substance is a filler found in the corneal stroma and attracts water due to the presence of what?

Glycosaminoglycans (GAGs)

Imbibition pressure is the negative pressure drawing fluid into the cornea. The IP of the cornea is approximately ___mmHg. 
Swelling pressure represents the stroma’s force to expand. SP of corneal stroma is ___mmHg.

IP: -40mmHg

SP: +55mmHg

Imibition pressure is equal to what?

IOP - Swelling pressure

Oxygen delivery to the cornea when the eyes are open is mainly from what? What about when the eyes are closed?

Open: atmospheric oxygen diffusion

Closed: palpebral capillaries

What are two ways for nutrients to be delivered to the cornea?

Leaky endothelium and limbal capillaries

Is glucose metabolism at the cornea mainly aerobic or anaerobic?

Anaerobic (85%) 

Which layer of the cornea maintains the shape of the anterior cornea when there is edema?

Bowman’s

What are the 3 players in the repair cascade for corneal regeneration?

Integrins, cytokines, and growth factors

The 3 players for corneal regeneration are integrins, cytokines, and GF. Match each one with their proper role.

1. Membrane glycoproteins that facilitate cell adhesion and formation of intercellular jxns

2. Signaling molecules for cell to cell communication

3. Moderate cell proliferation and differentiation

Integrins: adhesion

Cytokines: cell to cell communication

GF: cell proliferation

List the following steps of epithelial healing in order.

a. Pause mitosis

b. GF and cytokines released from damaged cells

c. Hemidesmosomes disassembled along edge of wound

d. Cell migration

e. Cell to cell jxns form

f. Mitosis resumes leading to increase in protein synthesis

In order

T/F In Bowman’s healing, there is regeneration and there will be no scar left.

False - does not regenerate and will scar

T/F There is a scar that is left after the corneal stroma heals

True