ophtho 1/17/17 Flashcards
eyelid anatomical structures
skin (thin, no subq fat)
eyelashes/follicles
tarsal plate (fibrous layer for shape and muscle attachment)
meibomian glands on underside of tarsal plate - secrete oil so tears resist evaporation
conjunctiva underside
tf
chalazion = stye
F
chalazion is granulomatous inflammation of meibomian gland (underside of tarsal plate for oil secretion to resist tear evaporation), not painful
stye is pimple-like infection of sebaceous gland or eyelash follicle, superficial to tarsal plate and painful
eyelid movement
muscles
innervation
orbicularis occuli closes, cn 7 (facial) like a fish hook (7)
levator palpebrae opens, cn III (occulomotor) like a pillar (III)
how will bell’s palsy affect the eyelid
inability to close - orbicularis occuli, cn7
how will occulomotor nerve palsy affect eyelid
ptosis (drooping, inability to open) levator palpebrae cn III
define
optic cup
optic disc
cup to disk ratio
where optic nerve and blood vessels enter retina
cup is center white pit w no nerve fibers
disk is entire thing including cup, pink rim is location of nerve fibers
ratio of .3 ish is normal (cup is 3/10 total diameter) ratio increases (empty cup expands) w increased pressure eg glaucoma
define conjunctiva
mucus membrane starts at edge of cornea (the limbus), covers sclera, loops to underside of eyelid
place at border of cornea where conjunctiva starts is called the
limbus
what structure prevents things like eyelashes and contact lenses from traveling behind eye
conjunctiva
covers scleral surface and continuous loop to inderside of eyelid
“pink eye”
aka
tissue of eye affected
conjunctivitis
conjunctiva
semilunar fold of the eye refers to…
thickened fold of conjunctiva at medial canthus
thickened fold of conjunctiva at medial canthus is called
semilunar fold
majority of tears produced by…
accessory tear glands located within eyelid and conjunctiva
Lacrimal gland (superolateral) is really only responsible for reflexive tearing
describe flow of tears
accessory tear glands in eyelid and conjunctiva mostly
lacrimal gland superomedially reflexively
down front of eye
out lacrimal punctum -2 small pores on superior and inferior medial canthus
down lacrimal tubing and into nose at inferior turbinate
% of lacrimal tubing (lacrimal puncta to inferior turbinate) non-patency in newborns
sx
tx
2-5% newborns
excessive tearing
often resolves spontaneously
sometimes metal probe to force open
how do eye drops meant for local effect achieve impressive unintentional systemic side effects, and how to avoid
via nasal mucosa when draining via tear duct into inferior turbinate
-direct route to circulatory system, skips liver
so watch out w beta blockers
-can squeeze medial canthus after dropping and close eyes for a few minutes to limit drainage into nose
the only nerve visible in vivo
optic nerve
(w ophthalmoscope)
-eye is direct extension of brain
sclera is composed of
collagen
tf
cornea is an extension of the sclera
t
but it is clear instead of white because it is dehydrated
the sclera is continuous with the…
cornea (clear because dehydrated)
optic sheath
chambers of the eye
anterior chamber - cornea-iris
posterior chamber - iris-lens
vitreous chamber - lens-retina
fluids of eye
vitreous humor - jello-like in vitreous chamber lens-retina
aqueous humor - watery w nutrients that fills post and ant chambers in front of lens and nourish avascular cornea and lens
define posterior vitreous detachment and risk
jelly vitreous humor can liquefy and fall in upon itself… normally benign but can tug on retina and create small retinal tears
majority of eye’s refractory power from…
air/cornea interface (2/3)
only 1/3ish refraction from lens
nutrient supply to cornea
tears
aqueous humor
peripheral limbus blood vessels
(cornea is avascular)
5 layers of cornea
epithelium - heals quickly, no scar bowman's layer (basement membrane of epithelium?) stroma - scars descemet's membrane (bm of endothelium) endothelium - don't regenerate
bowman's bell tower (high) descement deep (deep)
why is corneal endothelial cell count important?
do not regenerate, cells just spread to cover more area
-if count too low, spread not good enough, aqueous can get in faster than endothelium can pump it out, cloud cornea with edema
uvea components
iris
ciliary body
choroid plexus
(all continuous with each other)
iris primary function
control amount of light in
sns dilates
psns constricts
define anterior chamber angle
between inner cornea and root of iris
-trabecular meshwork and schlemm’s canal for aqueous drainage
function of ciliary body
secrete aqueous humor
contract to relax zonula fibers and relax lens
define the choroid of the eye
bed of blood vessles that lies under retina, supplying outer one-third of retina (rods and cones), which can die off if separated by retinal detachment
nutrition to lens
aqueous humor
highest protein concentration of any tissue of body
lens]
35% protein, 65% water
3 layers of lens
capsule - shell of mm
cortex - chocolate of mm
nucleus - peanut of mm
consistency of lens capsule
saran wrap
consistency of lens nucleus
hard
contraction of ciliary body causes zonule ligaments to..
relax (sphincter shrinks)
lens rounds out for more refracting power eg for reading
define presbyopia
age-related hardening of lens so it does not round out so well for reading – starts after age 40 and almost everyone over 50 needs reading glasses
which are deeper, in retina, ganglion nerves or photoreceptors
photoreceptors are deeper
light must pass through ganglion layer to get to them
fovea nourished by
choroid
so susceptible to injury in retinal detachments
bones of orbit
frontal - roof zygomatic - lateral maxillary - floor lacrimal ethmoid - medial greater sphenoid (and little palatine bone) - posterolateral
thinnest bone of orbit
lamina papyracea of ethmoid bone medially (paper-thin)
-sinus infections can erode thru and cause orbital cellulitis
orbital bone that breaks most often in trauma
maxillary bone floor
-blowout fracture, enopthalmia (sunken eyeball), entrapment of inferior rectus muscle
(medial wall thinnest but buttressed by surrounding structures…)
define orbital apex
bony entry point for all nerves and vessels supplying orbit
- to superior orbital fissure between wings of sphenoid bones
- annulus of zinn is a muscular band that tops the superior orbital fissure and serves as origin of four rectus muscles w optic nerve passing right through
nutrition to retina
deep 2/3s from retinal vessel
superficial 1/3 (closest to light) from choroid plexus
which muscle does not originate at the orbital apex?
inferior oblique
originates from orbital floor
Which full-thickness eyelid laceration is more dangerous – medial or lateral lacerations? Why?
You worry about the canalicular tear-drainage system involvement with medial lacerations. You want to repair this system as soon as possible, to avoid chronic epiphora.
How does the water content of the cornea differ from the rest of the eye?
The cornea is relatively dehydrated, which helps with clarity. If water gets into the cornea, via a disrupted endothelium or a high pressure gradient from acute glaucoma, the cornea turns hazy and white.
A pseudophakic (i.e. implanted lens) patient is found to have excellent far vision, but reading is terrible. What’s going on?
As we get older, our natural lenses harden and do not change shape very well making it hard to accommodate and see near objects. This phenomenon is called presbyopia and is a normal finding in people over 40 years of age. A PROSTHETIC LENS IS NOT ABLE TO CHANGE SHAPE at all, so all patients (including small children) with implanted plastic lenses require reading glasses to read.
densest tissue in the body
lens
highest protein conc lowest water conc
how do funglasses improve vision
yellow tint blocks blue
eliminates chromatic aberration (diff colors diff wavelengths refract differently strike retina differently so can’t focus at all perfectly at once)
phakic
pseudophakic
aphakik eye
phakic - natural lens
pseudophakic - artificial lens
aphakik eye - no lens
define lens accomodation
lens rounding for increased refraction for near-sight
-ciliary body contraction relaxes zonula fibers
most common type of cataract
nuclear sclerotic cataract
lens, especially the dense nucleus, becomes larger and brunescent (yellow/brown), obstructive opacity and glare problems, eventually push iris forward, angle closure glaucoma
define morgagnian cataract
far-advanced nuclear sclerotic cataract liquifies cortical layer and hard nucleus falls to bottom of capsular bag
difficult to remove at surgery
rare in developed countries
“second sight” from cataracts
inflexible aged presbyopic lens resistant to accomodation, but then developing nuclear sclerotic cataract causes outward bulge with better refraction so older pt can read better again, working like weak bifocal
define posterior subcapsular cataract and risk factors
opacity on back of lens on surface of posterior capsule bag - significant vision problem despite innocuous slit-lamp appearance because posterior location closer to nodal point of lens with more rays passing thru
- steroids, dm, ocular inflammation
- often occure with some nuclear sclerotic cataract
which are more significant, posterior or anterior cataracts of similar size
small posterior more sig than large anterior
posterior location closer to nodal point of lens with more rays passing thru
mgmt of congenital cataract
get it out quickly, usually within 2 mos of life, to avoid amblyopia
-wait a few years to implant prosthesis because eye still growing – powerful aphakic glasses or contact lenses till child old enough for lens implants
pathogenesis of traumatic cataract
outer lens capsule breaks
inner lens swells with water and opacifies
innervation and blood supply to adult lens of eye
none
nutrition from aqueous humor
pathogenesis of episodic blurring vision in diabetic
prescribe glasses?
lens survives on glycolysis because low O2 tension because nutrition from aqueous, no blood supply or innervation
- high glucose, lens metabolisims shunts down sorbitol pathway (via aldose reductase), sorbitol buildup, osmotic swelling of lens, increased refraction, temporarily near-sighted
- check recent glucose, get under control, don’t prescribe glasses because may be transient
basics of cataract surgery
suck out cortex and nucleus
stick a prosthetic in the capsular bag
posterior capsular opacification
define
treat
not a true cataract
happens w cataract surg after sucking out nucleus and cortex and implanting prosthetic in capsular bag
-residual lens epithelial cells get confused and lonely and can migrate along back surface of implant and opacify the posterior capsular bag
-easily treated in clinic w YAG laser capsulotomy to blast away excess epithelial cells
name types of cataracts
nuclear sclerotic cataract
posterior subcapsular cataract
congenital cataract
traumatic cataract…
causes of lens dislocations
trauma
inherited dz affects zonular strength (marfan, homocystinuria)
marfan dz inheritance pattern protein appearance eye effects
autosomal dominant
fibrillin
tall body habitus, arachnodactyly
UPWARD lens subluxation (zonula fibers weak)
-astigmatism (distorted images from looking thru angulated lens)
astigmatism
a deviation from spherical curvature of eye or lens
results in distorted images, as light rays are prevented from meeting at a common focus.
homocystinurea inheritance pattern protein appearance eye effects systemic effects
autosomal recessive
nonfunctional cystathionine b-synthetase
(can’t convert homocysteine to cystathionine)
marfanoid habitus, 50% mental retardation
brittle breaking zonules without good cysteine
(largely composed of cysteine)
DOWNWARD lens dislocations usually
poor peripheral circulation and thromboembolic risk under general anesthesia
when is a cataract “ripe” for surgery
when vision a major problem
-no objective cataract size or metric… diff people experience different sx w diff cataract characteristics… eg wimpy cataract can cause big problem, big cataract can cause minimal problem
-20/50 a guideline - driving vision in most states
(but needs different for airline pilot…)
-also underlying retinal disease that needs to be examined, like diabetic retinopathy - no good if cataract prevents exam
presentation of glare problems from cataract
stopped driving at night
test glare in clinic
check vision while shining a light
or formally w brightness acuity tester device
(illuminated hemisphere w vision hole in the middle… looks kind of like a hand mirror a bit curved w light and a hole in the middle - induces glare)
why not cataract surgery when vision drops to 20/25
surgical risks…
evolution of cataract surgery
egyptians dislocate lens and let fall to bottom of eye, basic outlines better than cloud
british ww2 pilots eyes tolerated penetrating plexiglas fragments
how to choose cataract implant power
must know
corneal curvature - larger curve, need more power
and depth of eye - shorter eye, need more power
perform cataract surgery
- anesthesia - topical tetravaine vs retrobulbar V1 CN3 CN6 block w lidocaine/bupivicaine (CN4 outside muscle cone, not blocked)
- enter eye via cornea or scleral tunnel (slower but easier to extend if complications)
- capsulorhexis - hole in capsule
- phacoemulsify - carve up lens nucleus
- remove cortex w suction - remnants may cause inlammation and “after cataracts” posterior capsule opacification
- insert the lens into capsular bag, or on top of capsule or behind iris or on top of iris depending on how bad things went wrong
- close eye - small self-closing vs 10-0 biodegradable nylon
- postop - abx (cipro vs moxi) and steroid drops
how many operations for basic cataract surgery proficiency
over 100
tough procedure
how can a cataract cause glaucoma?
bulk can push iris forward - angle closure
also end-stage cataracts can leak proteins into aqueous humor and inlammatory cells (macs) can clog trabecular meshwork
“after cataract”
posterior capsular opacification
from epithelial migration to posterior capsule after successful cataract surgery
YAG laser to treat
what is the “sulcus” of the eye?
between iris and lens capsule
e.g. can place prosthetic lens here if posterior capsule torn during surgery
drops to give after cataract surgery
abx (cipro vs moxi (vigamox)
steroid to decrease inflammation
common systemic disease that can be first detected with eye exam
diabetes
specific HPI ROS for ophtho
- floaters and flashing lights - retinal detachment, retinal tears… floaters more important if new or worsening
- transient vision loss - migraine vessel spasm in young, microemboli in elderly, curtain ischemia or detachment
- blurry vision - when reading or watching tv not blinking dry, glare at night cataracts, dm poor control lens swelling
- redness pain - scratchy achy photophobic discharge
- headaches, scalp tenderness - temporal giant cell arteritis… jaw claudication, polymyalgias, weight loss, night sweats
focus of family history in ophtho pt
glaucoma (make sure pt not confusing for cataracts)
blindness
allergy alert in glaucoma pt
sulfa allergy
sometimes give Diamox to control eye pressure
Diamox
generic
moa
acetazolamide reversible inhib of carbonic anhydrase dec H+ secretion into renal tubule inc renal excretion of Na K HCO3 H2O -Dec production of aqueous humor -inhib in cns to retard abnormal and excessive discharge from cns neurons...
focus of meds in optho pt
eye drops
beta blocker
“vital signs” of eye exam
-vision
(snellen, if can’t - count fingers at distances, if can’t - hand motion and light… also pinhole - if no improvement start thinking visual impediments like cataracts or other media opacities))
-pupils (reaction, consensual response, accomodation cross eyed, swinging light test for APD)
-pressure (tonometer - measures force to flatten predetermined area of corneal surface)
how does pinhole vision work
improves vision (unless eg cataract or other media opacity) by decreasing refractory variation from different rays at different angles, so only straight on pinhole ray gets thru and easy to focus on retina
check for afferent pupillary defect APD aka
Marcus Gunn Pupil
swinging light test
should constrict (dilate a bit while passing over nose) and constrict again
-positive APD if constrict one side dilate other side because afferent defect (partially blind so does not constrict as much, appears to dilate… eg retinal issue… nerve issue distal to optic chiasm…)
older presbyopic pts need a (+ or - ?) power lense to help them read
+ power lens
eg +2.50
for more refractive power
because presbyopic lens stuck flat
describe fluorescence, eg fluorescein for eye
absorbs one specific wavelength and emits another
e.g. fluorescein absorbs blue light and emits green
beyond eye “vitals” - vision pupils pressure… what else in eye exam?
peripheral fields
EOM
if diplopia
-monocular - refractive error (astigmatism, cataract, corneal surface wrinkling… not neurologic)
-binocular - misalignment between eyes (neuromuscular paralysis or muscle entrapment) - determine which gaze direction improves vs worsens doubling
8 components of slit-lamp exam
EXT external - symmetry ptosis proptosis conjunctivitis - preauricular submandibular submental nodes
LL lids and lacrimation - infection irritation
CS conjunctiva and sclera - icteric, injected (blanch w epi?)
K cornea
AC anterior chamber - cell and flare (protein smoke), depth
I iris - flat and pupil round, neovascularization
L lens
V vitreous
conjunctival injection signifies
red inflamed conjunctival blood vessels
fundus exam comments
M macula - flat? good light reflex?
V vessels - av nicking? attenuation?
P periphery - lattice, cobble-stoning, tears?
D disk - cup:disk ratio, rims pink and healthy?
ways to view fundus of eye
direct ophthalmosocope - typical practitioner
indirect ophthalmoscope - head-set w more powerful hand lens
slit-lamp - best most powerful
tips for direct ophthalmoscope fundus exam
very dark
get close
dilate eye if possible
five “vital signs” of ophthalmology
vision pupil pressure confrontational fields eom
most common cause of marcus gunn pupil
optic nerve/tract lesion or infarct
afferent pupillary defect - swinging light test
describe “cell and flare” in ophtho
inflammation in anterior chamber
flare - like projector thru smoke, protein smoke
cell - dust specks in smoke, cells
before starting beta blocker eyedrops to control eye pressure in glaucoma pt, ask about these medical conditions
asthma
heart problems
define glaucoma
death of optic nerve
several theories - assoc if not entirely due to intraocular pressure… stretching, sheer forces, vascular compromise, hormone dysregulation..)
most common type of glaucoma in usa
open angle (80%) (microscopic or idiopathic clogging of trabecular meshwork)
“acute” glaucoma aka
closed angle glaucoma
opthho emergency, can lose vision in horu’s
rate of vision loss
open vs closed angle glaucoma
open - over many years, from chronically elevated IOP from microscopic or idiopathic clog of trabecular meshwork
closed - within hours, from irido-corneal angle closure
risks for chronic open angle glaucoma
FH age (^40) race (af am) high IOP large vertical optic nerve cupping thin corneas - mechanism not understood but we check corneal thickness because they seem predisposed to optic nerve damage
open angle glaucoma mechanism
(idiopathic usually)degeneration of trabecular meshwork filter, Impaired drainage (vs complete block in acute closed angle),
aqueous humor backup
chronically elevated IOP
progressive destruction of ganglion nerves in the retina
(possible mechanisms include stretching, vascular compromise, glutmate transmisison issues)
loss of vision
why is open-angle glaucoma a “sneaky thief of sight”
gradual vision loss so pts don’t realize till far advanced
so screen pressure and/or peripheral vision loss
classic physical exam for open angle glaucoma
elevated eye pressure
optic disk changes
repeatable visual field loss patterns
normal intraocular pressure
8 - 22 mmHg
device for measuring IOP
and by what principles does it work
this is analagous to…
tonometer
force applied to distort cornea a standard amount
aka resistance of the cornea
like pressing bike tire to check air inside
tf
IOP fluctiates throughout the day
t
highest in morning
variable to consider when using tonometer to measure IOP
corneal thickness
-calibrate pressure reading accordingly
id ganglion atrophy caused by chronic open angle glaucoma on physical exam
cup to disk ratio ^.5
or asymmetry between of disks between eyes
is suggestive
on fundoscopic exam
tf
cup sits directly in the middle of the optic disk
f
slightly off-center
beacuse optic nerve enters at an angle
which rim of optic disk is thickest
ISNT Inferior - thickest superior nasal temporal - thinnest
ISNT rule deviation in open angle glaucoma
normally inferior rim of disk is thickest and temporal is thinnest
-in glaucoma often vertical thinning and notching of inferior and superior rims (blood vessels dive out of view of rim edge)
how to map vision loss from chronic open angle glaucoma
automated perimetry (machine maps out peripheral vision)
what vision is lost first in open angle glaucoma
peripheral
central typically spared
(late stage mayhave 20/20 central but legally blind because no peripheral)
primary treatment strategy for open angle glaucoma
decrease eye pressure
because it is the only risk factor we can treat
medical treatment of chronic open angle glaucoma
eyedrops
- beta-blockers dec aqueous humor production (most traditional therapy, but systemic se’s if nasally absorbed so ask re asthma copd cardiac problems)
- alpha-agonists
- carbonic anhydrase inhibitors dec aq hum production
- prostaglandins (newest, increase aqueous humor OUTflow, se’s eyelash growth (some like it) may darken iris color blue or green to brown)
surgical treatment for chronic open angle glaucoma
shunt vs laser
trabeculectomy - alternate drainage pathway from superior limbus (cornea meets iris) incision to subconjunctival space - antimetabolites like mitomyocin-c to site to prevent rapid healing… or plastic tube-shunt from anterior chamber to plate under conjunctiva more posteriorly
-ALT argon laser trabeculoplasty to burn and scar open trabecular meshwork, or burn ciliary body to dec aqueous humor production
most common mechanism of acute glaucoma
pupillary block (lens plasters up agains iris blocking aqueous flow thru pupil -pressure gradient across iris forces lens and iris forward and closes irido-corneal angle, blocking trabecular meshwork, inc pressure w more aqueous, retinal damage from stretching and decreased blood supply
does tobramycin cover pseudomonas?
y
Vigamox
generic
moxifloxacin
tf
acute glaucoma is a medical emergency
t
define hyperope
far-sighted person w small eye
race predisposed to developing angle closure glaucoma
asians
typical inciting condition of acute glaucoma
pupil dilation
-eg in dark, movie theater, stressful situation (SNS), antihistamines and cold medications that may dilate the eye
iris gets thicker and irido-corneal angle gets smaller
acute glaucoma presentation
- setting of pupil dilation -eg in dark, movie theater, stressful situation (SNS), antihistamines and cold medications that may dilate the eye (iris gets thicker and irido-corneal angle gets smaller)
- extremely red painful eye, often nausea / vomiting, halos around lights (corneal stroma edema from pressure forcing in fluid)
- pupil sluggish and MID-DILATED, pressures very high (often 60mmhg or higher) - can palpate pressure difference
key exam in acute glaucoma
measure pressure
asess anterior chamber angle (shine pen light across and see shadow if iris pushed forward, vs gonioscopy - anterior chamber viewing w lens w mirrors on sides placed directly onto cornea)
why is gonioscopy needed to view anterior angle
can’t be viewed w raw microscope because total internal reflection (air-cornea interface creates complete mirror for light at that angle so light from angle can’t get out of cornea (like fiber-optic cable or flying fish escape strategy)
-gonioscope is lens w glass sides placed directly on cornea to break cornea-air interface and mirrors provide angle to see acute angle
treat acute glaucoma
decrease pressure in eye asap
- topical timolol b block diamox ca inhib dec aqueous humor production
- systemic glycerin iv mannitol (or even ethanol in a bind)
- miotic pilocarpine to constrict pupil open outflow angle
- topical glycerin to transiently dehydrate cornea for better exam
if recurrent
-laser iridotomy to open flow bewteen post and ant chamber, relieve pressure gradient, let iris go back to normal position, open trabecular meshwork (usually performed bilaterally because predisposed in both eyes)
neovascular glaucoma
path
tx
dm or retinal vein occlusion
produces VEGF for ischemic retina neovascularization
VEGF can float thru eye and stim neovascularization of iris, fibrous membrane at iris-corneal angle blocks outflow and forms open-angle glaucoma… eventually neovascularization can pull iris forward and cause essentially irreversible closed-angle glaucoma
-laser peripheral retina to dec ischemic demand for angiogenic VEGF… eventually probably need surg like tube-shunt..
pigment dispersion synrome
path
pres
dx
pigmented back surface of iris rubs against radial zonules supporting lens, pigment flecks shed into aqueous and clog trabecular meshwork drain, may also stick to inner-corneal surface in a vertical line (Krukenberg spindle) due to convection currents in aqueous
- typically young white males w myopic eyes eg after exercise inc iop
- gonioscopic visualization of trabecular meshwork, even trans-illumination defects of iris on slit-lamp
pseudoexfoliation syndrome of eye
path
systemic condition where basement-membrane material deposited throughout body… adheres to anterior capsule of lens, creates rough surface and when iris moves over it pigment rubs off and clogs trabecular drain
(zonular instability too, makes cataract operations difficult)
fundamental difference open vs closed angle glaucoma
open is common, chronic, IMPAIRED not completely blocked aqueous humor drainage
closd is acute irido-corneal angle closure blocking ALL aqueous drainage – an ophtho emergency that can lead to blindness
monitor progression of glaucoma
pressure disk fields
iop
optic disk changes
visual fields
how will thin cornea affect iop measurement
iop will be underestimated…
what kind of vision loss in glaucoma?
mid-periphery to start usually
central vision typically spared till late
