OS 212 - Ophtha Flashcards
orbit shape
pear
orbit volume in adults
30 cc
barrier between eyelid and orbit
orbital septum
bones forming roof of orbit
frontal, sphenoid (lesser wing)
bones forming lateral wall of orbit
sphenoid (greater wing), zygomatic
bones forming floor of orbit
maxillary, zygomatic, palatine
bones forming medial wall of orbit
ethmoid, lacrimal, frontal, maxillary, sphenoid
wall of the orbit comprised of the most bones
medial wall
entry site of all nerves and blood vessels to the eye
orbital apex
structures passing through lateral SOF
superior ophthalmic vein, lacrimal, frontal, trochlear nerves
structures passing through medial SOF
superior and inferior oculomotor nerve, abduscens and nasociliary nerves
structures passing through optic canal
optic nerve, ophthalmic artery
supplies retina
central retinal artery
supplies lacrimal gland
lacrimal artery
supplies upper eyelid
lacrimal artery
supplies ciliary body
long posterior ciliary arteries
supplies sclera, episclera
anterior ciliary arteries
supplies limbus
anterior ciliary arteries
supplies conjunctiva
anterior ciliary arteries
supplies choroid
short posterior ciliary arteries
supplies eyelids
medial palpebral arteries
drainage of the eye
superior and inferior ophthalmic veins
drains into ophthalmic veins
vortex veins, anterior ciliary veins, central retinal vein
analogue of nictitating membrane
semilunar fold of bulbar conjunctiva
location of accessory lacrimal glands
fibrous layer of conjunctival stroma
accessory lacrimal glands
glands of Krause and Wolfring
layer of the conjunctival stroma not present at birth
adenoid layer
source of conjunctival arteries
anterior ciliary and palpebral arteries
innervation of conjunctiva
CN V1
fibrous membrane covering globe from limbus to optic nerve
Tenon’s capsule
parts of Tenon’s capsule at limbus
conjunctiva, Tenon’s capsule, episclera
suspensory ligament of Lockwood
IR + IO + Tenon’s capsule
thinnest portion of sclera
at insertion of recti muscles, 0.3mm (half as thick)
contains BV that nourish sclera
episclera
T/F: The cornea is thicker at the periphery
T
T/F: The cornea is wider vertically
F, wider horizontally (11.75mm)
five layers of the cornea
epithelium, Bowman’s membrane, stroma, Descemet’s membrane, endothelium
comprises 90% of corneal thickness
stroma
modified corneal stroma
Bowman’s membrane
basal lamina of corneal epithelium
Descemet’s membrane
maintains corneal deturgescence
endothelium
effect of disruption of corneal endothelium
corneal edema
T/F: Corneal endothelium is highly mitotic
F, has minimal capacity for cell division
mechanism of corneal endothelial repair
hypertrophy and sliding, NO mitosis
innervation of cornea
CN V1
attributed to corneal transparency
deturgescence, uniform structure, avascularity
comprises uveal tract
iris, ciliary body, choroid
middle vascular layer of eye
uvea
characteristic of iris capillaries
non-fenestrated
controls amount of light entering eye
pupil (dilates and constricts accordingly)
responsible for pupillary constriction
parasympathetic CN III
innervation of iris
fibers of ciliary nerve
2 zones of ciliary body
pars plicata, pars plana
part of ciliary body with ciliary processes
pars plicata
produces aqueous humor
ciliary processes in pars plicata of ciliary body
types of fibers of ciliary muscles
longitudinal, circular, radial
internal portion of choroid
choriocapillaries
nourishes outer portion of retina
choroid/choriocapillaries
structure/shape of lens
biconvex, avascular
normal lens thickness
4 mm
normal lens diameter
9 mm
connects lens to ciliary body
zonules
liquid compartment anterior to lens
aqueous humor
liquid compartment posterior to lens
vitreous humor
T/F: Lens cortex is harder than the nucleus
F
T/F: Lamellar fibers of the lens are poorly mitotic, thus leading to poor eyesight in old age
F, its continuous production causes the lens to become larger and less elastic
water content of lens
65%
T/F: The lens can feel pain
F, there are no pain nerve fibers on the lens
volume of aqueous humor
230 uL
rate of aqueous humor production
2.5 uL/min (subject to diurnal variation)
aqueous humor pathway
ciliary processes -> posterior chamber -> pupil -> anterior chamber -> trabecular drainage -> Schlemm’s canal -> venous system
main anatomic structures of anterior chamber angle
Schwalbe’s line, trabecular meshwork, scleral spur
demarcated by Schwalbe’s line
end of corneal endothelium
anterior extensions of retina
ora serrata
parts of retina without subretinal space
disc, ora serrata (other areas prone to retinal detachment)
10 layers of the retina
retinal pigment epithelium (inner layer of ciliary Bruch’s membrane), photoreceptor layer, external limiting membrane, outer nuclear layer (photoreceptor bodies), outer plexiform layer (photoreceptors to bipolar and horizontal cells), inner nuclear layer (bipolar, amacrine, horizontal cell bodies), inner plexiform layer (amacrine and bipolar cells to ganglia), ganglion cell layer, nerve fiber layer, internal limiting membrane
T/F: Retina is thicker at the posterior pole than anterior (ora serrata)
T, 0.56mm thick posteriorly and 0.1 mm thick anteriorly
location of macula
center of posterior retina
location of fovea
center of macula
retinal avascular zone in fluoroscein angiography
foveal reflex
photoreceptors in foveola
cones only
blood supply of retina
outer 1/3 - choriocapillaries, inner 2/3 - central retinal artery
sole blood supply of fovea
choriocapillaries
T/F: The fovea is able to repair itself after macular detachment
F, damage is irreparable
characteristic of retinal blood vessels
non-fenestrated, forms inner BRB
location of outer BRB
level of RPE
location of macula with respect to OD
temporal
part of retina first hit by light
inner limiting membrane
comprises 2/3 eye volume and mass
vitreous humor
outer surface of vitreous
hyaloid membrane
attachment of vitreous base
pars plana, immediately behind ora serrata
T/F: Vitreous attachment to optic nerve and lens capsule persists throughout life
F, formed early in life but soon disappears
origin of recti muscles
annulus of Zinn
longest and thinnest EOM
SO
only EOM not originating from orbital apex
IO
spiral of Tillaux
connects recti insertions to sclera (MILS)
blood supply of EOM
branches of ophthalmic artery
additional blood supply to LR
branch of lacrimal artery
additional blood supply to IO
branch of infraorbital artery
hairless prominence between eyebrows
glabella
layers of the eyelid
skin, orbicularis oculi muscle, areolar tissue, tarsal plates, palpebral conjunctiva
main support of eyelid
tarsal plates
closes eyelid
orbicularis oculi (palpebral)
innervation of orbicularis oculi
CN VII
length of lid margin
25-30 mm
width of lid margin
2 mm
parts of anterior lid margin
eyelashes, glands of Zeis (modified sebaceous glands), glands of Moll (modified sweat glands)
contains meibomian glands
posterior lid margin
passage of tears for drainage
lacrimal punctum (medial end of posterior lid margin)
number of lacrimal punctum per eye
2 (superior and inferior)
opens upper eyelids
levator palpebrae superioris, Muller’s muscle (superior tarsal)
opens lower eyelids
inferior rectus, inferior tarsal
innervation of lacrimal gland
lacrimal nerve (CN V1 – sensory), great superficial petrosal nerve (secretory), sympathetic nerves
drains lacrimal gland
ophthalmic vein
tear drainage pathway
lacrimal gland -> lacrimal puncta -> canaliculi -> common canaliculus -> lacrimal sac -> nasolacrimal duct -> nasal meatus
number of axons in optic nerve trunk
1.2M from ganglia of retina
types of optic nerve fibers
80% visual, 20% pupillary
visual fibers vs. pupillary fibers
pupillary fibers bypass lateral geniculate body towards pretectal area
T/F: Ganglial cells are capable of regeneration
F, being part of CNS, they can’t
color with shortest wavelength
violet (380 microns)
color with longest wavelength
red (760 microns)
visible spectrum
380-760 microns
change in speed of light from air to water (increasing refractive index)
slows down
direction of light deviation in a prism
towards base
structure of diverging lens
> < (-)
structure of converging lens
<> (+)
unit of measurement of lens power
diopter (D), 1/focal length
factors affecting lens power
lens curvature, difference in refractive indices
total converging power of human eye
60D - 40D cornea, 20D lens
parallel light rays dall into pinpoint focus on retina
emmetropia
types of ammetropia
myopia, hyperopia, astigmatism
focus point in myopia
in front of retina
focus point in hyperopia
behind retina
causes of myopia/hyperopia
axial (eyeball length), refractive (corneal curvature)
correction of myopia
divergent lenses (negative)
correction of hyperopia
convergent lenses (positive)
astigmatism
uneven curvature of cornea/lens at different meridians
correction of astigmatism
cylindrical lenses
types of astigmatism
simple (myopic/hyperopic), compound (myopic/hyperopic), mixed
physiologic changes in accommodation
pupils constrict, eyes converge, lenses thicken
presbyopia
loss of focusing/accommodating power in old age (>40 yo)
correction of presbyopia
convergent lenses (positive)
number of photoreceptors in mature retina
120M rods, 6M cones
senses perceived by retina
light, form, color
components of visual pigments
Vit A + opsin
components of rhodopsin
cis-retinal Vit A + opsin
mechanism of conversion of light to impulses
light -> rhodopsin cleavage -> hyperpolarzation (Ca permeability); energy released through cis->trans conversion of retinene
minimum visual angle of Snellen big “E”
5 minutes
minimum visual angle of arms of Snellen big “E”
1 minute
determinant of visual acuity
form sense
color blindness: ‘prot(o)-‘
red
color blindness: ‘deuter(o)-‘
green
color blindness: ‘tri-‘
blue
color blindness: ‘-anomaly’
deficiency in color
color blindness: ‘-anopia’
loss of color
cone monochromats
only one color
rod monochromats
achromats, totally color blind
pattern of inheritance of color blindness
sex-linked, recessive
monocular vs. binocular vision
monocular - complete decussation; binocular - partial decussation
visual relay pathway
retina -> CN II -> optic chiasm (partial decussation) -> optic tracts -> LGN -> optic radiations (temporal/parietal) -> strial cortex (occipital)
images received by occipital lobe
C/L images; (e.g. left lobe receives right hemi-field images)
decussating images at optic chiasm
images from temporal hemi-fields (images from nasal half of retina)
images relayed by optic tract
C/L images; (e.g. left tract relays right hemi-field images)
visual field defect: optic nerve
I/L anopia
visual field defect: optic chiasm
bitemporal hemianopia
visual field defect: optic tract
C/L homonymous hemianopia
visual field defect: temporal optic radiation
C/L superior homonymous hemianopia (pie in the sky)
visual field defect: parietal optic radiation
C/L inferior homonymous hemianopia (pie on the floor)
visual field defect: occipital lobe
C/L homonymous hemianopia
types of eye symptoms
abnormalities of vision, abnormalities of ocular appearance, abnormalities of ocular sensation
abnormalities of vision
vision loss, visual distortion, flashing/flickering lights, floaters, oscillopsia, diplopia
abnormalities of ocular appearance
red eye, color abnormalities, miosis, focal mass, proptosis, strabismus, abnormal size
abnormalities of ocular sensation
pain, irritation, headache
BOV algorithm
sudden/gradual? mild/severe?; sudden mild - suspect dry eye; sudden severe - suspect CRAO; gradual mild - suspect error of refraction; gradual severe - suspect cataract or glaucoma
DDx: BOV
refractive error, ptosis, ocular media disturbance, retinal dx, CN II dx, visual pathway abnormalities
DDx: glare/photophobia
corneal edema, cataracts; irritation, foreign bodies, acute inflammation, error of refraction, mydriasis, scratches on glasses, hazy ocular media
DDx: visual distortion
CSCR, ARMD; migraine, strong correction, macular and CN II lesions
DDx: flashing/flickering
retinal detachment, posterior vitreous detachment; retinal traction, posterior vitreous detachment, migrainous scintillations/aura
DDx: floaters
vitreous condensations; normal vitreous strands, pathologic pigments, blood, inflammatory cells
DDx: oscillopsia (shaking vision)
nystagmus; lid twitching (myokymia), nystagmus
DDx: diplopia
monocular (error of refraction, media abnormalities, corneal irregularities, lens dislocation)
DDx: red eye with swelling
preseptal cellulitis, orbital cellulitis, external hordeolum
DDx: red eye without swelling
conjunctivitis, iritis, acute glaucoma, scleritis, pterygium, subconjunctival hemorrhage
DDx: periocular pain
lid, tear sac, sinuses, temporal artery tenderness
DDx: retrobulbar pain
orbital inflammation, orbital myositis, optic neuritis
DDx: ocular pain
corneal abrasion, corneal foreign body, glaucoma, corneal ulcer, endophthalmitis
DDx: nonspecific pain
accommodation fatigue, binocular fusion, tension/fatigue referred discomfort
DDx: itching
allergic sensitivity
DDx: dryness
dry eye, mild corneal irritation
DDx: tearing
ocular surface irritation, (with edema) abnormal lacrimal drainage
DDx: watery secretion
allergy
DDx: mucoid discharge
allergy, viral conjunctivitis
DDx: ropy/stringy discharge
allergy
DDx: mucopurulent secretion
bacterial/viral conjunctivitis
DDx: copious purulent secretion
gonococcal conjunctivitis
DDx: bloody discharge
viral conjunctivitis, SJS
DDx: dried crusts on lashes
blepharitis
DDx: headache
errors of refraction, presbyopia, migraine, sinusitis, high and low BPs, intracranial pressure, closure glaucoma
DDx: headache + nausea + vomiting
increased intracranial pressure
DDx: U/L headache from I/L eye + nausea + vomiting
closure glaucoma
parts of basic eye exam
VA, gross (eye and adnexae, pupil), EOM, IOP, fundoscopy
methods of measuring decreased vision
move closer to 1 m -> finger counting -> hand movement -> light projection -> light perception -> NLP
parts of gross examination
eye position, eyelids and eyelashes, conjunctiva and sclera, cornea and iris, pupil
parts of pupul examination
size and shape, light reflex, swinging flashlight
normal pupil size
2-4mm
affected part if (-) consensual and direct pupillary responses
efferent arm of involved eye (given vision is normal)
affected part if (+) RAPD
optic nerve of dilating eye (consensual > direct response); I/L lesion
purpose of swinging flashlight test
r/o U/L CN II lesion or asymmetry
normal IOP
10-21 mmHg (with both eyes at least within 2 mmHg of each other)
c/i of tension tonometry
suspected globe perforation
used for indentation tonometry
Schiotz tonometer
cons of Schiotz tonometer
affected by scleral rigidity, patients must be supine
findings in tension tonometry
soft, hypotonic, firm
gold standard for IOP measurement
applanation tonometry
used for applanation tonometry
Goldman Applanation tonometer
c/i of applanation tonometry
patients with corneal abnormalities (e.g. scars)
cons of applanation tonometry
needs special equipment, needs ophthalmologist, affected by corneal thickness and irregular corneal curvatures
used for mass measurement of IOP
air puff noncontact tonometer
structures to observe in fundoscopy
ocular media (ROR), optic disc (ddb, CDR), retinal vasculature (AVR), retinal background (h/e, color) , macular area (foveal reflex, h/e)
normal CDR
< 0.5
cause of increased CDR
glaucoma -> death of ganglion cells
forms optic cup
aggregation of ganglion cells from retina
course of retinal BV temporally
arching
course of retinal BV nasally
radial
retinal structure with light reflex stripe
retinal arteries
normal AVR
2:3-4:5
DDx: Drusen lesions
ARMD
DDx: dot hemorrhages
diabetes
DDx: submacular hemorrhage
ARMD
DDx: hard exudates
HTN, DM, vHLD, radiation
DDx: soft exudates
HTN, DM, CTdx, HIV
DDx: boat hemorrhage
trauma, blood dyscrasia, sudden increase in IOP
DDx: flame hemorrhage
HTN, RVO, blood dyscrasia, trauma
DDx: vitreous hemorrhage
HTN, DM, trauma
