HEENT 01: Eye/Head Anatomy

Question 1

What is the sclera?

Answer 1

white outer protective layer

Question 2

What is the choroid?

Answer 2

vascular layer that provides oxygen and nutrients to eye

Question 3

What is the retina?

Answer 3

neural tissue containing photoreceptors

Question 4

What is the bulbar conjunctiva?

Answer 4

clear mucous membrane that covers sclera up to cornea

Question 5

What is the palpebral conjunctiva?

Answer 5

lines inside of eyelids

Question 6

What is the cornea?

Answer 6

modified transparent sclera that allows light to enter eye

• not covered by conjunctiva

Question 7

What is the optic disk?

Answer 7

where optic nerve leaves eye

• does not respond to light (known as blind spot)

Question 8

What is the macula?

Answer 8

yellowish pigmented spot at back of eye that contains fovea

Question 9

What is the fovea?

Answer 9

thinned-out, cone-only portion of retina where visual acuity is greatest

• rods predominate outside fovea
• eyes are normally moved so that light rays coming from object fall on fovea

Question 10

What are the layers of the retinal epithelium? (6)

Answer 10

• pigmented epithelium: absorbs light
• outer nuclear layer: contains photoreceptors, rods, and cones
• outer plexiform layer
• inner nuclear layer: contains cell bodies of various types of excitatory and inhibitory interneurons including bipolar cells, horizontal cells, and amacrine cells
• inner plexiform layer
• inner limiting membrane: boundary between retina and vitreous chamber

Question 11

What is age-related macular degeneration?

Answer 11

progressive, chronic disease of central retina that results in rapid vision loss if untreated

Question 12

What are the 2 processes of age-related macular degeneration?

Answer 12

• dry: geographic atrophy
• wet: exudative

Question 13

What is dry age-related macular degeneration?

Answer 13

(geographic atrophy)

• yellow lipid deposits (drusen) form under retinal epithelium
• loss of retinal epithelium, capillaries, and photoreceptors

Question 14

What is wet age-related macular degeneration?

Answer 14

(exudative)

• neovascularization of choroidal blood vessels into retina, leaking fluid, lipids and blood, leads to fibrous scarring
• treatable at certain stage, but permanent atrophic damage to fovea with loss of central vision (scotoma) can occur

Question 15

What are the risk factors for age-related macular degeneration? (4)

Answer 15

• cigarette smoking
• obesity
• low intake vitamin A, C, E, and zinc, lutein, omega-3 fatty acids
• cardiovasular risk factors – hypertension, hyperlipidemia, hypercholesterolemia

Question 16

What are some non-pharmacological/lifestyle measures for age-related macular degeneration? (4)

Answer 16

• stop smoking
• weight loss
• antihypertensive and lipid/cholesterol lowering therapies (if indicated)
• dietary supplements containing vitamins C and E, β-carotene, and zinc may delay progression

Question 17

What is the treatment for wet age-related macular degeneration?

MOA

Answer 17

suppress action of vascular endothelial growth factor (VEGF) – key regulator of neovascularization pathogenesis (angiogenesis and vascular permeability)

Question 18

What is the treatment for wet age-related macular degeneration?

Drugs (3)

Answer 18

• ranibizumab – antibody fragment that binds VEGF isoforms
• bevacizumab – antibody against VEGF (off-label)
• aflibercept – acts like VEGF receptor

Question 19

What is the pathogenesis of hydroxychloroquine-induced retinal toxicity?

Answer 19

• bilateral, ‘bulls eye’ pattern of retinal damage
• central, concentric, parafoveal
• progresses centrally towards fovea

Question 20

What are the risk factors for hydroxychloroquine-induced retinal toxicity? (4)

Answer 20

• duration of use (> 5 years, high cumulative dose > 1 kg)
• concomitant treatment with tamoxifen
• significant renal disease (> 50% decline in GFR)
• pre-existing retinal and macular disease

Question 21

How does hydroxychloroquine induce retinal toxicity?

Answer 21

• hydroxychloroquine inhibits uptake of all-trans-retinol (vitamin A) by retinal pigment epithelium cells (RPECs)
• photoreceptors contain rhodopsin (rods) or photopsin (cones) – GPCR that contains retinal
• vitamin A is precursor of retinal, therefore this depletes retinal in RPECs

Question 22

What is the management strategy for hydroxychloroquine-induced retinal toxicity?

Answer 22

screen for retinal toxicity initially during first year of treatment, and annually after 5 years of therapy

• no relationship between blood levels and retinal toxicity established, but hydroxychloroquine tends to accumulate in tissues
• hydroxychloroquine has very long half life (40-50 days) – after stopping therapy, negative effects on retina can continue for months
• dose should be < 5 mg/kg to maximum daily dose of 400 mg to limit retinal toxicity

Question 23

What is the lacrimal gland?

Answer 23

secretes tears spread over eyeball by blinking, and remove dust and foreign particles

• parasympathetic innervation – VII nerve via pterygopalatine ganglion
• drains via nasolacrimal duct

Question 24

What is dacryostenosis?

Answer 24

obstruction of nasolacrimal duct

Question 25

What is dacryocystitis?

Answer 25

infection of lacrimal sac - S. aureus - S. pneumonia - H. influenzae - S. marcessans - P. aeruginosa

Question 26

What are the symptoms of dry eyes (xerophthalmia)?

Answer 26

- discomfort – redness, burning, stinging, foreign body sensation, pruritus - visual disturbances – photophobia

Question 27

What is the pathological changes contributing to dry eyes (xerophthalmia)? (40

Answer 27

- dry eye with reduced tear production (aqueous deficient) - dry eye with ↑ evaporation of tear film (hyperevaporative) due to dysfunction of meibomiam glands - combination of the above - late stage associated with conjunctival scarring and corneal complications (kerastitis)

Question 28

Describe the muscarinic receptors of lacrimal glands.

Answer 28

parasympathetic nerve activate M3 receptor on secretory globular acinar cell to stimulate tear secretion

Question 29

Describe the muscarinic receptors of conjunctiva.

Answer 29

parasympathetic nerves acting on M3 receptors cause goblet cells in conjunctival epithelium to release mucin and other protein secretion into tear for eye lubrication

Question 30

What drugs can cause dry eyes and how?

Answer 30

anticholinergics (muscarinic receptor antagonists) - block activation of M3 receptor - ie. antihistamines

Question 31

What is Sjogren's syndrome?

Answer 31

incurable autoimmune disorder of mucous membranes that leads to dryness of eyes, mouth, skin, nasal, and vaginal passages - mostly in women - can have antibodies to M3 receptor – thought to disrupt lacrimal and salivary gland function, leading to dry mouth (xerostomia) and dry eyes (xerophthalmia) - symptoms may be treated with muscarinic receptor agonists (along with artificial tears, saliva)

Question 32

What is conjunctivitis (pink eye)?

Answer 32

inflammation of transparent lubricating mucous membrane that covers globe of eye and under surface of eyelid

Question 33

What are the symptoms of conjunctiva? (3)

Answer 33

- discharge – purulent, mucopurulent, or watery - erythema - pruritis

Question 34

What causes conjunctivitis? (3)

Answer 34

- allergic conjunctivitis: seasonal allergies (most frequent) - viral: adenovirus - bacterial: H. influenzae in infants and toddlers, S. aureus in older children and adults

Question 35

What is external hordeolum (stye)?

Answer 35

staphylococcal infection of hair follicle of (upper) eyelid - produces pimple-like abscess that can swell and reddening eyelid that can be painful

Question 36

What causes external hordeolum (stye)?

Answer 36

blocking of zeis gland (secrete sebum) and moll gland (produce IgA, mucin, lysosomes) due to thickening, drying, or stasis of their secretions promotes infection

Question 37

What is internal hordeolum?

Answer 37

infection of meibomiam gland (sebaceous gland that produce oily layer to help with lubrication) in conjunctiva - more painful

Question 38

What is chalazion?

Answer 38

cyst-like nodules that remain after hordeolum heals - normally red, but not painful

Question 39

What is blepharitis?

Answer 39

inflammation of eyelids, often at base of eyelashes - erythematous, pruritic eyelids, conjunctival injection, crusting or matting of eyelids, and occasionally flaking of eyelid skin