optho anatomy

Question 1

what are the 3 layers of the eye?

Answer 1

1) innermost retinal layer: nueral retina + retinal pigment epithelium
2) choroid layer: middle vascular layer, contains choroid, iris, ciliary body
3) corneoscleral layer: outer fibrous layer contains sclera and cornea

Question 2

What are the 3 chambers of the eye?

Answer 2

1) anterior chamber: cornea, iris, lens; aqueous humor
2) posterior chamber: iris, lens, zonule fibers, ciliary body; aqueous humor
3) vitreous humor: lens, zonule fibers, retina; gelatinous vitreous humor

Question 3

the retina develops from what structure?

Answer 3

primitive diencephalon–>optic vesicle–>optic cup

• inner layer optic cup: neural retina
• outer layer of optic cup: retinal pigment epithelium

Question 4

what primitive layer does the cornea develop from?

Answer 4

ectoderm

Question 5

retinal pigment epithelium

Answer 5

nutritional support for photoreceptors; absorbs stray light; phagocytoses shed membrane material from outer segments of photoreceptors

Question 6

photoreceptors

Answer 6

carry out phototransduction to convert light into neural activity

Question 7

interneurons of retina

Answer 7

process signals from photoreceptors

Question 8

ganglion cells of retina

Answer 8

transmit signals from interneurons to the brain via the optic nerve

Question 9

fovea/macula

Answer 9

contains all cones, no blood vessels and cell spreading to form a pit
-maximize high acuity color vision

Question 10

optic disk/optic papilla

Answer 10

origination of optic nerve; no photoreceptors=functional blind spot

Question 11

ora serrata

Answer 11

multilayered neural retina simplifies into single layer columnar epithelium that is not photoreceptive

Question 12

choroid

Answer 12

highly vascularized, pigmented loss CT layer

Question 13

ciliary body

Answer 13

regulates fine focus by adjusting shape of lens
contains ciliary muscle (smooth muscle) with parasympathetic innervation
zonule fibers connect ciliary body to lens

Question 14

what is the source of aqueous humor?

Answer 14

ciliary processes

Question 15

Iris

Answer 15

adjusts the amount of light entering the eye by changing the size of the pupils

• contains 2 sets of muscles:
  1) dilator pupillae (myoepithelial cells): sympathetic innervation; dilate pupil
  2) constrictor pupillae (smooth muscle): parasympathetic innervation, constrict pupil

Question 16

sclera

Answer 16

covers posterior 5/6 of eye
dense opaque connective tissue
point of insertion of extraocular muscles

Question 17

cornea

Answer 17

• covers anterior 1/6 of eye
• transparent, avascular
• major refractive element of the eye w/ 5 layers

Question 18

limbus

Answer 18

point of transition from sclera to cornea

• location of canal of schlemm which drains aqueous humor
• if drainage is blocked–>glaucoma

Question 19

opacification of lens

Answer 19

cataracts

Question 20

conjunctiva

Answer 20

lines inner surface of eyelid

-composed of stratified columnar epithelium with goblet cells

Question 21

lacrimal gland

Answer 21

• tubuloalveolar serous gland that secretes tears; large lumens and few ducts
• looks like pancreas w/o islets

Question 22

myopia

Answer 22

• light rays from distant objects are focused in front of the retina
• causes: eyeball is too long, refraction is too strong
• presents as blurred distance vision, near vision is usually good
• tx: concave lens, refractive surgery

Question 23

hyperopia

Answer 23

• Light rays from distant objects are focused behind retina
• Overcome in early life by great ability for accommodation
• Vision problems start occurring as accommodation weakens

Causes:
• Eyeball is too short
• Refraction is too weak

clinical:
• Presents later in life
• Youth: no symptoms (accommodation)
• Adulthood: blurred near +/- distance vision

tx:
• Convex lens (+)
• Refractive surgery

Question 24

astigmatism

Answer 24

-light rays are not refracted uniformly–>multiple points of focus
Causes: non-spherical cornea (egg shaped), non-spherical lens
-clinical: blurry vision
-tx: cylindrical lens, refractive surgery

Question 25

presbyopia

Answer 25

part of normal aging process - decreased accomodative ability-->cant bring near objects into focus - patients hold reading material far away - tx: convex lens

Question 26

aphakia

Answer 26

Absence of the lens, which results in the eye being short 20 diopters of refracting power -can be corrected by things that offer convex power: thick glasses, contact lens, lens implant

Question 27

esotropia

Answer 27

eye turned in

Question 28

exotropia

Answer 28

eye turned out

Question 29

hypertropia

Answer 29

one eye higher than the other

Question 30

hypotropia

Answer 30

one eye lower than the other

Question 31

strabismus

Answer 31

misalignment of the visual axes of the eyes due to the eyes not working together

Question 32

comitant strabismus

Answer 32

- deviation is consistent regardless of gaze - NO known neuromuscular etiology - Common in children

Question 33

incomitant strabismus

Answer 33

- Deviation size increases when the gaze is in the direction of the involved muscle - Causes include CN palsy, thyroid eye disease, MG and mechanical obstruction - Less common than comitant strabismus

Question 34

congential esotropia

Answer 34

- comitant strabismus - Seen in infants in the first few months of life - Amblyopia is common - Treatment is surgery

Question 35

accommodative esotropia

Answer 35

- comitant strabismus - Develops between ages 1-4 - Occurs in children who are very hyperopic (farsighted) - Intermittent at first, but increases over time - Amblyopia is common - Excess accommodation → excess convergence (esotropia) - Treatment is glasses (reduces excess accommodation) - Many children can wean off of glasses by teenage years - Outcome is extremely good

Question 36

sensory esotropia or exotropia

Answer 36

- comitant strabismus - Occurs in eye with poor vision - Treatment is with surgery - Surgery straightens eye, but does NOT improve vision - Surgery often needs to be repeated within 15 years

Question 37

idiopathic exotropia

Answer 37

- comitant strabismus - Begins intermittently, but increases in frequency and duration - Usually more severe at distance - Amblyopia is common - Treatment is observation +/- eventual strabismus surgery

Question 38

CN 3 palsy

Answer 38

- incomitant strabismus - Patient presents with ptosis, eye pointed down and out and dilated pupil - Levator muscle weakness → ptosis (droopy eyelid) - CN3-innervated EOM weakness → eye pointed “down and out” - Pupillary fibers weakness → dilated pupil - Mechanism may be congenital, trauma or aneurysm - Very difficult to treat, but some patients do well with surgery

Question 39

CN4 palsy

Answer 39

- incomitant strabismus - Patient presents with vertical diplopia and a head-tilt away from bad side - Involves the superior oblique muscle - Mechanism may be congenital or trauma - Treatment for mild vertical diplopia is glasses with a prism - Treatment for severe vertical diplopia is surgery

Question 40

definition of amblyopia

Answer 40

impairment of vision without any detectable organic lesion of the eye

Question 41

causes of amblyopia

Answer 41

* Refractive (49%): one eye has more far-sightedness, more near-sightedness or more astigmatism than the other eye (rarely, the cause may be bilateral abnormalities) * Strabismus (49%): alignment of the eyes such that the image does not fall on one (or both) of the maculas * Ocular Pathology (2%): cataract, glaucoma or corneal anomaly

Question 42

What do you correct before you correct strabismus?

Answer 42

amblyopia!

Question 43

development of amblyopia

Answer 43

o Until the age of 7, poor vision will result if a clear image is not focused onto the fovea of each eye o This is a CNS problem, and will occur even if the eye is structurally completely normal o The earlier the onset of amblyopia, the worse the prognosis

Question 44

when do you patch a child's eye

Answer 44

before the age of 7! -patch the strong eye to force the child to use the weaker eye and improve the amblyopia * Must be a sticky, bandaid-like patch * Amount of time patient needs to wear patch to improve vision is related to two things: * Degree of initial visual impairment * Age at time of first noticing amblyopia (the younger the age, the less patch time needed) * Once vision is improved, patient must continue to wear patch 1 hour per day until age 8-9 When patches absolutely do not work you can dilate the good eye with atropine