Cataract Flashcards
(160 cards)
1
Q
What conditions are associated with weakened zonules?
A
• PXF
• Prior vitreoretinal surgery
• Trauma
• High myopia
• Connective tissue disorders (Marfan’s, homocystinuria,
hyperlysinemia Ehler Danlos, scleroderma,
Weil-Marchesani)
• Uveitis
• Retinitis pigmentosa
2
Q
What are the absolute contraindications for LASIK?
A
• Asymmetric bowtie
• Areas of superior or inferior thinning
• Ectatic disorder: keratoconus, pellucid marginal
degeneration, keratoglobus
• Thin central cornea
• Residual stromal bed <300 μm
• High preoperative potassium values
• Young age
3
Q
What refractive change can occur after scleral buckle?
A
• Myopic shift secondary to axial elongation
4
Q
What are the 3 main sources of error when calculating IOL power in post-refractive surgery eyes?
A
- Radius error (true central K is flatter than K reading
obtained from instruments) - Keratometer index error (index of refraction assumes a
certain ratio between the radii of curvature of anterior
and posterior corneal surface) - Formula error
All of these lead to hyperopic surprise
5
Q
What are the types of topographic maps and what types of corneal power do they measure?
A
• Axial power map/sagittal curvature map: based upon
reference axis through line of sight and better
estimation of central corneal power
• Instantaneous/tangential or meridional map: gives
corneal power based on best fit spherical
approximation at corneal point measured and is better
estimation of peripheral corneal power
6
Q
What is photoablation?
A
• Use high-energy ultraviolet photons to break covalent
chemical bond, no heat is produced
• Excimer laser (193 nm)
• Used in keratorefractive procedure
7
Q
What is photocoagulation?
A
• Head generated by absorption of light denatures
protein
• Used in retinal photocoagulation (PRP)
• Laser thermokeratoplasty (LTK) treat hyperopia
8
Q
What is photodisruption?
A
• Wavelength produced by the Nd-YAG laser. This type of
laser is pulsed, so the energy it produces is released in
a very short time, producing a large amount of
momentary power
• The laser beam is focused into a small area. In the
vicinity of the focus, electrons are stripped from their
atoms by ionization, but they quickly recombine, which
produces a spark and an acoustic wave
• During a photodisruption procedure, it is the
mechanical (acoustic) wave and not the laser light itself
that breaks the capsule.
9
Q
What is photoactivation?
A
• The conversion of chemical from one form to another
by light
• Clinical application includes verteporfin used in PDT
10
Q
What type of cataract is associated with Alport syndrome?
A
• Anterior lenticonus (bilateral)
11
Q
What is the most common ocular complication with chronic hyperbaric oxygen?
A
• Nuclear sclerotic cataracts, results in myopic shift
• ~50% of patients exposed to hyperbaric oxygen >150
times during 1-year period will develop cataracts
12
Q
What is orthokeratology?
A
• Rigid CL that is flatter than the cornea to push down on
the cornea, cause remolding of corneal epithelium
• Treats low orders of myopia
• 73% experienced CL discomfort in the clinical trial,
corneal edema occured in large number of patient
13
Q
What is aqueous misdirection syndrome?
A
• AKA ciliary block glaucoma
• Aqueous is directed into vitreous instead of flowing
through pupil
Treatment: mydriasis and cycloplegia (phenyl 10% and
atropine), aqueous suppressants, hyperosmotic. If medical
treatment fails → disruption of anterior hyaloid face with
YAG laser or PPV
14
Q
What are the most common gases used in excimer lasers?
A
• Argon and Fluorine
15
Q
What are the wavelengths of different lasers?
A
• Femtosecond: 1053 nm (infrared)
• Excimer: 193 nm (UV light)
• Nd:YAG: 1064 nm
• Rhodopsin most sensitive at 510 nm (green light). Less
absorption of blue and yellow light. Cannot absorb
longer wavelengths (red)
16
Q
What is Fuchs heterochromic iridocylcyitis?
A
• Chronic uveitis; long and fragile vessels that cross angle
and insert high in angle (25% nicked when entering AC)
• Unilateral without severe pain or photophobia
• Stellate KPs
• Iris heterochromia (blue eyes appear dark; brown
appear lighter)
• Lack of anterior/posterior synechiae
• PSC 75%
• Difficult to control glaucoma (will likely require surgery)
Treatment: not necessary to treat inflammation, focus on
glaucoma screening/management and cataract removal
17
Q
Where are lens epithelial cells mitotically most active?
A
• Anterior pre-equatorial capsule
18
Q
What are the different types of CL and duration of holiday needed before normalization on topography?
A
• Soft spherical CL: 3-14 days
• Soft toric lens: 2 weeks or more
• Rigid contact lens: at least 2-3 weeks (causes epithelial
migration), additional month for every decade of hard
contact lens wear
19
Q
What are limbal relaxing incisions?
A
• 600 microns in depth
• Just anterior to limbus ~2 mm
• Done on steep meridian
• Maintain spherical equivalent (coupling ratio = 1)
20
Q
What is arcuate keratotomy?
A
• 95% in depth
• Placed at 7 mm optical zone
• Done on steep meridian
• Maintain spherical equivalent (coupling ratio = 1)
• Flattening in the meridian of incision and steepening 90
degrees away (coupling)
21
Q
What is spherical aberration ?
A
• Higher order aberration (4th order)
• Decrease in quality of vision after refractive surgery
• Peripherally refracted light rays are focused in front of
retina and central rays are focused on the retina
• Halos around point light sources night myopia
• Decreased contrast sensitivity
22
Q
What is the most serious complication of piggyback lenses?
A
• Interlenticular opaque membrane
• Most commonly occurs when two acrylic IOLs are used
especially if they are both placed in the capsular bag
23
Q
What are transversion incisions?
A
• Straight incisions
• Parallel to limbus
• Coupling ratio >1
• Hyperopic shift
24
Q
What is coupling ratio?
A
• Amount of flattening induced by incision
• Amount of steeping induced 90 degrees away
25
What is corneal Collagen cross-linking?
• Strengthens stabilize cornea
• Used in ectatic corneal disorders (KCN, PMD,
post-refractive ectasia)
• Expose cornea to riboflavin (B2) and UVA
• Increases rigidity of cornea and reduce ectatic process
• UVA light penetrates 300 μm and can destroy
endothelial cells.
• Corneal thickness at least 400 μm prior to UVA
• If cornea not thick enough, use hypotonic riboflavin
until cornea swells over 400 μm
• Contraindications: Corneal thickness <400 μm, prior
herpetic infection, central corneal scarring, poor
epithelial healing, severe dry eye, autoimmune
disorders
26
What is chatter?
• Nuclear fragment repelled by phaco tip
• Not desirable because lens can’t be aspirated
efficiently
• Allows lens pieces to have greater chance of striking
corneal endothelium
• Happens when ultrasound stroke > vacuum
• To decrease chatter-reduce phaco power which
reduces stroke length of phaco tip or increase vacuum
setting
27
What is duty cycle?
• Proportion of time phaco energy is applied during
specified period of time
28
What is stroke length?
• Distance phaco tip travels
• Usually 2-4 mil (1 mil=1/1000 of inch)
29
What is cavitation?
• Shock waves that are released as gas bubble implodes
at phaco tip
• Due to compression and expansion of gas atoms
• Shock waves helps break down lens fragments so they
can enter phaco tip
30
What is the pathway responsible for diabetic cataracts?
• Sorbitol pathway
31
What are the findings of Keratoconus?
• Ectatic disorder
• More common starts at puberty
• Maximal thinning at apex
• Asymmetric steepening
• Scissoring with retinoscopy
• Fleischer ring
• Scarring is common
32
What is Pellucid marginal degeneration and its finding?
• Less common, onset 20-40s
• Maximal thinning inferior to area of protrusion
• Scarring only after hydrops
• Crab-claw confirmation on topography
33
What are the findings of Keratoglobus?
• Very rare, onset at birth
• Thinning greatest in periphery
• Protrusion in generalized
• No iron line or scarring
34
What is against-the-rule astigmatism?
• Football sitting on one of its poles (horizontal
meridian is shorter)
• Too much power along horizontal meridian
• Cylinder correction that provides focusing power
vertically no additional power horizontal
Treatment:
• Minus cylinder vertically (exerts power long its axis)
• Positive cylinder horizontally (exerts power 90
degrees away)
35
What is with-the-rule astigmatism?
• Football lying on its side
• Steepest part of cornea along vertical meridian
• Cylinder correction that provides focusing power
horizontally no additional power vertical
Treatment:
• Negative cylinder at 180 degree (exert power along
its axis)
• Positive cylinder at 90 degrees (exert power 90
degrees away)
36
How many days prior to surgery should anti-platelet be stopped so normal platelet function is restored?
• 10 days, i.e. Aspirin, clopidogrel, vitamin E
• Hold for ocular surgeries at risk of suprachoroidal
hemorrhage (PKP, glaucoma surgery)
37
What is Glaukomflecken?
• High IOP during angle closure glaucoma lead to lens
epithelial death leads to gray-white anterior
subcapsular opacities
• Pinpoint opacities measuring 2-3 mm or more in size
38
What is Brown Mclean syndrome?
● Peripheral corneal edema after cataract extraction
● Edema begins several years after surgery
● Corneal edema characteristics:
○ Peripheral 2-3 mm
○ Central cornea spared
○ Starts inferiorly and extends circumferentially
○ Punctate brownish pigmentation, localized
guttae
○ No neovascularization of cornea
○ Associated with long term aphakia
○ After routing cataract surgery, vitrectomies
○ No etiology
Most are asymptomatic, may complain of foreign body
sensation secondary to ruptured bullae
39
What are zero order, 1st order, and 2nd order aberrations (lower order aberrations)?
• Zero order: piston
• 1st order: vertical and horizontal prism
• 2nd order: myopia, hyperopia, regular astigmatism
40
What is the rate of visually significant PCO?
● 28% at 6 years
● Rate of formation for different intraocular lens (lowest
to highest):
Acrylic < silicone < PMMA
● Occurs when lens epithelial cells migrate across
posterior capsule and cause contraction of secreted
collagen matrix, this can result in capsular wrinkling
and PCO
41
What is a Soemmering Ring?
• After cataract surgery, residual lens epithelial cells
proliferate in closed space between anterior and
posterior capsules.
• Consists of nucleated bladder cells = Wedl cells
42
What is an Elschnig pearl?
• Epithelial cells proliferate in large spherical aggregates
like “fish eggs” where each “ fish egg” is nucleated
bladder cell
43
What are the risk factors for choroidal hemorrhage?
• Older patients (brittle choroidal blood vessels)
• Glaucoma
• Previous hemorrhage in fellow eye with intraocular
surgery
• Myopia
• Hypertension
• Arteriosclerosis
• Bleeding diathesis
• Recent trauma or surgery with active inflammation
• Prolonged hypotony
• Anticoagulation
44
What is the minimal residual stromal bed thickness needed for LASIK?
• 250 microns, most leave > 300 microns
45
What situation is associated with highest rate of endophthalmitis after cataract surgery?
• Hypotonous eye with leaking wound
• Leaking wound acts as conduit for bacteria to enter
eye
46
What is the holding force?
• Force that is exerted on the nuclear piece when tip if
fully occluded
47
What is Epi-LASIK?
• Blunt microkeratome to remove epithelium, then
ablate stromal bed
• Plane of separation is between basement membrane
and Bowman’s layer
48
How is LASEK performed?
• Place alcohol on epithelium, remove epithelium,
laser the bed, then replace epithelium back on the
stromal bed
• Plane of separation is between lamina lucida and
lamina densa
• Leaving behind lamina densa may provide better
postoperative refractive result compared to
epi-LASIK (controversial)
49
What is PRK?
• Scrape epithelium off with brush or spatula then
ablate stromal bed
50
What are the various forms of potential acuity estimation for cataract evaluation?
• Potential acuity pinhole (PAP): read a brightly lit
near card through standard pin line aperture. Dilate
prior to this test
• Potential acuity meter (PAM): projecting Snellen
chart through tiny aperture. Projected chart is
moved around patient pupil until clear path is
obtained and patient can see projected Snellen chart
• Laser interferometry (LI): Projects 2 separate laser
beams onto retina. 2 light beams interfere with each
other creating a diffraction fringe pattern on the
retina. Pattern independent of lens opacities.
Spacing of the fringe pattern is decreased until
patient cannot distinguish separate lines, may
sometimes overestimate potential acuity
51
What is photostress recovery time?
• “Poor man’s electroretinogram”
• Bright light is shined into patient’s eye for 10
seconds through undilated pupil
• The time required before patient can read BCVA line
or one line larger = photostress recovery time
• >90 seconds indicates significant maculopathy
• Distinguishes optic nerve disease from macular
disease
52
What are the Y sutures in lens?
• Anterior upright Y suture
• Posterior inverted Y suture
• Y sutures appear around 8 weeks of gestation
53
What is a posterior chamber phakic intraocular lens (PIOL)?
• Used in refractive surgery when patient has
contraindications to corneal refractive surgery
• Lenses are flexible collamer material, inserted
through small corneal wound into ciliary sulcus
• “Vaulted” over crystalline lens to prevent contact
with it
• Space between PIOL and crystalline lens allows
aqueous to flow over crystalline lens which prevent
cataract formation
• Ideal space 0.5-1.5 corneal thickness
• Vault less than 250 micron → risk of anterior
subcapsular cataract
• Vault greater than 750 microns → risk of crowding
angle and pupillary block glaucoma, iris chafing
54
What is the most common type of cataract in acute diabetes?
• Cortical in nature-snowflake cataracts
55
What are the causes of AC shallowing during cataract surgery?
• Inadequate infusion of BSS
• Leakage through oversized incision >3.0 mm
• External pressure on globe (improper speculum, too
tight surgical drapes, tight eyelids, too much
retrobulbar anesthesia)
• Posterior vitreous pressure (obese, thick neck,
COPD)
• Suprachoroidal hemorrhage
Shallow AC can lead to radialization of capsulorhexis,
more phaco energy transmitted to corneal endothelium,
repeated iris prolapse through main wound
56
What is diffuse lamellar keratitis (DLK)?
• Interface inflammatory process that begins as
dust/sand-like infiltrate in interface of periphery
• Untreated → stromal melting and corneal scarring
with resulting irregular astigmatism
• Associated with epi defects, occur during LASIK,
foreign material lodged in interface, contamination
of sterilizer with gram negative endotoxin
57
What are the different grades of diffuse lamellar keratitis (DLK)?
• Grade 1: peripheral faint WBCs, no central corneal
involvement - Tx topical steroids, follow q2-3 days
• Grade 2: WBC migrated to central cornea - Tx topical
steroids, consider interface irrigation, follow q1-2
days
• Grade 3: dense WBC clumped in central cornea,
beginning of corneal scarring; "threshold DLK"
permanent visual morbidity if treatment is not
initiated; typically occurs post op day #2 or 3 - Tx lift
flap, clean interface, intensive topical steroids
consider oral steroids
• Grade 4: stromal melting and permanent corneal
scarring, hyperopic shift, "mud cracks," poor
prognosis even with above treatments
58
What is accommodation?
1. Ciliary muscle contracts
2. Zonular tension decreases
3. Axial lens thickness increases
Hardening of lens is primary cause of loss of
accommodation (presbyopia) because a harder lens will
prevent increase in convexity that occurs with ciliary
muscle contraction
Helmholtz theory of accommodation = most
accommodative change in lens shape occurs at the
central anterior lens surface; posterior capsule does not
change at all with accommodation
59
What is the difference in ablation pattern in hyperopic LASIK versus myopic LASIK?
• Myopic: center of bed is lasered to flatten cornea,
make cornea less dioptrically powerful
• Hyperopic: periphery of bed is lasered to steepen
cornea and make cornea more dioptrically powerful
• Once ablation is complete, flap is laid back down
60
What is the mechanism by which mitomycin C application after surface ablation prevents corneal haze?
• Reduces number of keratocytes and their enzymatic
activity
(activation of keratocytes after surface ablation
leads to haze, keratocytes lay down collagen and
glycosaminoglycans)
61
What is the most common type of congenital and infantile cataracts?
• Lamellar or zonular cataracts
• Lamellar cataract: opacifications of specific zones
within lens; typically bilateral and symmetric
62
What is TASS (toxic anterior segment syndrome)?
• Sterile inflammatory reaction
• Secondary to contaminants injected into the eye or
incorrect pH of irrigating solutions
• Commonly occurs when remnants of cleaning
detergents are not properly washed out of reusable
cannula
• Presents in acute post-op period (12-24 hours),
earlier than acute endophthalmitis (2-7 days)
• Confined to anterior segment
• Treatment: exclude endophthalmitis as cause of
inflammation; intensive topical steroids; control IOP
if elevated
63
What is Ectopia lentis et pupillae?
• Iris with slit-like configuration that is displaced in
opposite direction as subluxed lens
• Autosomal recessive
64
What is the most common postoperative complication of LASIK?
• Dry eye – secondary to transection of corneal nerves
with flap creation
65
What is AcuFocus corneal inlays?
• AKA alloplastic corneal inlay porous ring segments
• Used in non-dominant eye of presbyopic patients
• Small central aperture causes increase in depth of
field
66
Where is the cellular ion pump located on the lens?
• Anterior lens epithelium cells
• Sodium-potassium-ATPase pumps sodium out of the
lens and potassium into the lens
67
What is conductive keratoplasty?
• Small circular burns are created in cornea to steepen
the central cornea
• Radiofrequency probe to heat points in the
peripheral cornea → causes localized collagen
shrinkage and corneal flattening around the points
and central corneal steepening
• Results in cornea that has more refractive power
• Used to correct low orders of hyperopia to create
monovision
Rarely used in following situations:
1. Cases of over-corrected myopia LASIK or PRK
2. Keratoconus to flatten the cone
3. Ectasia
68
What is phacolytic glaucoma?
• Lens proteins leaks through an intact capsule
• Lens proteins are taken up by macrophages
• Engorged macrophages and lens protein itself can
clog trabecular meshwork
69
What is lens particle glaucoma?
• Macroscopic portions of lens (mainly cortex)
remains unnoticed after cataract surgery
• These pieces make their way to anterior chamber
and directly clog trabecular meshwork
70
What is phacoanaphylactic uveitis?
• AKA phacoantigenic uveitis
• Immune-mediated granulomatous inflammation
that is elicited by lens proteins released through
ruptured lens capsule
• Typically trauma is the cause of this ruptured lens
capsule
• Can also occur if cortical material is left in the eye
after cataract surgery
• Granulomatous uveitis occurs days to weeks after
inciting event
71
What is phacomorphic glaucoma?
• Lens becomes so large it pushes iris forward and
closes angle
72
What type of cataract is most common in patients with atopic dermatitis?
• Anterior subcapsular
• Generally bilateral shield-like anterior subcapsular
cataracts
• Occur in up to 25% of patients with atopic dermatitis
• Onset 2nd/3rd decade
73
What is the most common side effect of conductive keratoplasty?
• Regression of effect
74
What is a zonular dialysis?
● Portion of bag detached from ciliary processes
● Occur secondary to ocular trauma or spontaneously
● Predisposed in PXF and Marfans
● Can occur due to inadequate hydrodissection and
overly aggressive rotation of lens nucleus
● If this occurs intraoperatively:
○ Prevent vitreous loss with possible lost lens
fragments
○ Prevent additional zonular damage
● Treatment: First inject abundant amounts of
viscoelastic → Then detached area of capsule needs
to be supported mechanically via capsular hooks or
capsular tension ring
75
What causes early postoperative shallow AC with high IOP versus with low IOP?
• Shallow AC with low IOP = wound leak
• Shallow AC with high IOP = posterior pushing
mechanisms 🡪 i.e. choroidal detachment
76
What are the types of lens crystallin?
• Alpha: highest molecular weight
• Beta: majority of crystallins by overall weight (55%)
• Gamma: minority of crystallins by weight
77
What are the ways in which excimer laser is delivered to cornea?
• Broad beam
• Flying spot
• Slit beam
78
How is radial keratotomy performed?
• Partial thickness linear radial cuts in cornea →
wound gape with mid-peripheral bulging of cornea
→ central cornea flattens → decreased refractive
power and therefore decreased myopia
79
What are the findings from Prospective Evaluation of Radial Keratotomy (PERK) study?
• 43% of patients had greater than 1D hyperopic shift
over 10 years
• 3% had irregular astigmatism
80
What are multifocal lens?
• Diffractive lens with rings that go out to the
periphery
• Rings on posterior aspect of optic
• True multifocal lens
• 2 focal points - one at distance and one at near
• No matter pupil size, diffraction causes near and far
images to be in focus
81
What is a Symfony lens?
• Diffractive lens
• Rings are apodized = gradual shortening of step
heights toward the periphery of diffractive zone,
allows for smoother transition from distance to
intermediate to near
• Extended depth of focus lens
82
What is a Restor lens?
• Diffractive lens
• Rings are apodized - smoother transition from near
to distance - extends to 3.6 mm
• Difficulty reading in low light if pupils normal size
83
What is a ReZoom lens?
• Multifocal images by refraction
• Associated with large amount of glare and halos
84
What is Crystalens?
• Accommodating intraocular lens
• With near stimulation and contraction of ciliary
muscle, silicone lenses either are anteriorly
displaced or steepen anterior curvature of optic
85
What is the preop scotopic pupil size that will likely result in glare and halos after refractive surgery?
• 7.0 mm
• Majority excimer lasers have optical zone on 6.5 mm
• Pupil larger than optical zone will result in halos
86
What is an implantable collamer lens?
• Maintains natural shape of cornea (prolate - steep
centrally and flatter peripherally)
• Aspheric shape reduces higher order aberrations
• (Most amount of aberrations due to radial
keratotomy also occurs with LASIK)
87
What layer of cornea is the graft in epikeratoplasty placed?
• Bowman's layer
• Pre-lathing a donor corneal stroma and then
suturing it to Bowman's layer
• Not very successful because carving out exact shape
is difficult → unpredictable refractive outcomes
• Trauma induced by eyelid blinking could sometimes
dislodge graft
• Epithelial ingrowth is also a problem
88
What type of cataract is seen with congenital rubella cataract?
• Pearly white nuclear opacifications; retention of cell
nuclei within lens fibers
• Rubella in 1st trimester: ocular (cataracts or
glaucoma), auditory (deafness) and systemic
(cardiac)
• Patients who develop rubella cataract do not
develop glaucoma, vice versa
• Rubella in 2nd trimester: salt and pepper fundus
89
What type of cataract is seen in retinitis pigmentosa?
• Posterior subcapsular
• RP also associated with CME and zonular weakness
90
What conditions are associated with PSC?
• Chronic steroid use
• Radiation exposure (brachytherapy)
• Chronic uveitis
• NF2
• Fuchs heterochromic iridocyclitis
• Retinitis pigmentosa
91
What is a wave-front guided ablation?
• Aberometer used to calculate lower and higher
order aberrations pre-operatively
• Laser then takes the information from aberometer
and applies a laser ablation that attempts to
minimize lower and higher order aberrations
92
What is a wave-front optimized laser?
• Surgeon enters patient’s preoperative Ks and
attempted correction into laser
• Laser has pre-programmed database of Ks and
corresponding ablation patterns that from
manufacturers testing has minimized higher order
aberrations
93
What are the risks factors for buttonholes?
• Increased risk with steep cornea (>48D)
• More common after creating a flap with
microkeratome
94
What are the ocular findings in myotonic dystrophy?
• Christmas tree cataract
• Ptosis
• Pigmentary retinopathy
• Ophthalmoplegia resembling CPEO
• Low IOP due to ciliary body detachments
95
What is major intrinsic protein?
• Protein expressed by lens fibers as they line up in
the bow region and correlated with elongation of
cell
• Cells elongate and the points where cells from one
side touch cells from the opposite side form sutures.
Then cells lose their nuclei
96
What is the difference between radial incisions and arcuate incisions?
• Radial incisions = flatten both in meridian of the
incision and 90 degrees away
• Arcuate incisions = flattening in meridian of incision
and steepen meridian 90 degrees away
97
What is postoperative CME?
• Peak incidence 6-10 weeks after cataract surgery
• 95% uncomplicated cases resolve spontaneously
• Topical NSAIDs + steroids speed up resolution than
either alone
98
What organism is responsible for chronic ocular inflammation after cataract surgery?
• Chronic P. acnes
• Occurring 6 weeks after surgery
• Typically responds to topical steroids and
appearance of PCO
• Culture and IVI antibiotics are indicated
• If no resolution → vitrectomy with partial capsular
bag removal, some require entire capsular bag and
IOL removed
99
What is laser interferometry?
• Two helium/neon lasers to create a fringe pattern
on retina
• Device has wavy patterns corresponding to visual
acuity
• Smaller distance between wavy lines corresponds to
finer visual acuity
100
What are the types of remnants of fetal vasculature?
• Bergmeister's papillae: remnant of hyaloid artery
• Pupillary strands: remnants of anterior pupillary
membrane
• Mittendorf dots: remnants of tunica vasculosa lentis
101
What is pressure-induced stromal keratitis (PISK)?
• LASIK complication classically caused by prolonged
topical corticosteroid use
• Steroid-response increase in IOP🡪causes fluid
accumulation within interface
• Measured IOP may be falsely low due to fluid acting
as "cushion“
• Check pressure in the peripheral cornea or using
dynamic contour tonometry
• May present with interface fluid cleft or diffuse
stromal and interface opacity
• Can be causes by anything that results in an acute
IOP rise
• Typically requires 10-21 days to develop (unlike DLK
= very early complication of LASIK)
• Anterior segment OCT aids in diagnosis
• Treatment: stop topical steroids and IOP lower meds
102
What is Holmium:YAG laser used for in refractive surgery?
• Photothermal effect
• Wavelength of 2.13 microns
• Procedure is called laser thermokeratoplasty
• Used for low hyperopia
103
What is an excimer laser?
• Photoablation, breaks carbon-carbon and
carbon-nitrogen bonds. M/C are argon-fluoride
lasers
• 193 nm wavelength
104
What are the types of viscoelastic agents?
• Viscoat = dispersive, better coating ability (protect
corneal endothelium better); more difficult to
remove from eye; lower molecular weight, less IOP
spike if left in the eye
• Provisc/Healon/Amvisc = cohesive agents; made
from hyaluronic acid; clump more (high surface
tension), more easily removed from the eye; higher
molecular weight; raise IOP more
105
What is an epithelial ingrowth in post LASIK? What are the risk factors?
• Epithelial cells are trapped underneath flap 🡪 these
cells can growth toward visual axis and cause
irregular astigmatism, foreign body sensation, flap
melts
• Risk factors: epi defect at time LASIK (more common
in ABMD, diabetics, frequent use of topical
preserved eyedrops), use of microkeratome for flap
creation
• Traumatic flap dehiscence
• Re-treatments requiring flap lift
Treatment: lift flap, scrape off epithelial ingrowth from
both flap and underlying stromal bed, reposition flap,
BCL
106
What is the Munnerlyn equation?
• Optical zone usually 6.5 mm2
• Residual stromal bed = CCT - flap thickness - ablation
depth
107
What is lens-iris-diaphragm retropulsion syndrome?
• AC deepening, extreme pupil dilation, concave shape
of iris, patient discomfort due to stretching of ciliary
body
• Risk factors: high myopia (stretched/thin zonules),
deep AC, previously vitrectomized eyes, incision size
• Cause: reverse pupillary block where iris contacts
anterior capsule 360 degrees. AC pressure greater
than PC/vitreous pressure. Pressure difference
causes marked deepening of AC and posterior
bowing of iris
• Treatment: lift iris off anterior capsule with phaco
tip/second instrument or I/A tip → break reverse
pupillary block and allow compartments to equalize
in pressure
108
What is the recommended time frame to remove bilateral versus unilateral congenital cataracts?
● Bilateral cataract:
○ Removed before age 10 weeks
○ Once cataract is removed, second cataract
should be removed <2 weeks for child <2 years,
<4 weeks for child >2 years
● Unilateral cataract:
○ Removed before age 6 weeks
109
What are the risk of intracameral aminoglycoside/gentamicin?
• Retinal toxicity
110
What is the pathophysiology of cataract formation?
• Increase in amount of water insoluble proteins
• Increase in urea insoluble proteins
• Increase in crosslinking between proteins
• Decrease in glutathione
111
What are the risk factors for intraoperative epithelial defects during LASIK?
• ABMD - loose anchoring of epithelium into abnormal
basement membrane
• Older age
• Manual microkeratome - moves across the eye
• Abundant use of preserved topical eyedrops - toxic
and loosens epithelium (tetracaine more toxic than
proparacaine)
112
What are intracorneal ring segments (Intacs)?
• Flatten cornea in keratoconus
• Improves refractive error
• Allows for better fitting of hard CLs
113
What is the definition of power in phaco?
• Percentage of length phaco tip moves relative to
maximal possible length
114
What is the definition of cavitation in phaco?
• Formation of bubbles at the phaco tip results in lens breakdown
115
What is the definition of load in phaco?
• Amount of surface area of nuclear material in
contact with phaco tip
116
What is the most common type of cataract that occurs secondary to trauma/contusion?
• Posterior star-like configuration/stellate
117
What are the risk factors for anterior capsular phimosis?
• Pseudoexfoliation
• Other causes of loose zonules (trauma, Marfan)
• Small capsulorrhexis
• Silicone IOL material
• Plate haptic IOLs
Treatment: YAG cap (more energy than posterior
capsulotomy)
118
What is intraoperative floppy iris syndrome and what causes it?
● Triad: iris prolapse into wounds, iris
billowing/floppiness, progressive pupillary miosis
● Causes:
○ α1a antagonists (tamulosin, terazosin,
doxazosin, alfuzosin, prazosin, silodosin)
○ Labetalol
○ Antipsychotics (chlorpromazine, quetiapine,
risperidone)
119
What is the corneal thickness cutoff for increased risk of corneal decompensation after cataract surgery?
• 640 microns
120
What type of IOL is ideal for a patient who has previously undergone myopic LASIK?
• Aspheric lens that contributes negative spherical
aberration
• Examples: AMO technis monofocal; Alcon SN60WF
• Sensitive to decentration
121
What type of IOL is ideal for a patient who has previously undergone hyperopic LASIK?
• Traditional spherical lens that induce some positive
spherical aberration or no spherical aberration –
softport lens
• For low hyperopic LASIK – aspheric neutral lens
122
What are the risk factors for diffuse lamellar keratitis?
• Solutions used to clean microkeratome
• Iodine prep
• Gram negative endotoxin
• Meibomian gland secretions
• Laser ablation debris
• RBCs in the interface
123
What conditions are associated with PAX6 mutation?
• WAGR syndrome
• Posterior embryotoxon
• Peters anomaly
• Axenfeld anomaly
• Congenital cataracts
124
What are the findings for the Endophthalmitis Vitrectomy Study (EVS)?
• Assessed endophthalmitis acutely after cataract
surgery
• 2 groups: immediate vitrectomy versus vitreous
culture + IVI antibiotics
• Majority of patients did better with simple tap and
inject
• ONLY patients with LP or worse vision benefited
from immediate vitrectomy
• Intravenous antibiotics is not of benefit once IVI are
given
125
What is the management for suprachoroidal hemorrhage?
• Should be closed with suture as quickly as possible
• Consider posterior sclerotomies, 5-6 mm posterior
to limbus and inferotemporal quadrant
126
What are the ocular effects of chlorpromazine and thioridazine?
• Pigment deposition on posterior cornea and anterior
lens capsule
• High doses of thioridazine → severe retinopathy
(initially RPE stippling in posterior pole then
nummular/coin-shaped pattern)
• Treatment: immediate cessation of drug
127
What are the advantages and disadvantages of femtosecond laser compared to microkeratome?
● Advantages
○ Center your flap easier
○ More reliable flap thickness
○ Less risk of epi defect, free caps buttonholes
○ Greater ability to adjust flap parameters (i.e.
sidecut angle, spot separation)
● Disadvantages
○ Longer suction and procedure time
○ Opaque bubble layer
○ AC bubbles
○ Increased postoperative pain
○ More expensive
○ Subsequent flap lifts more difficult
128
What are the differences between micro- and macrostriae after LASIK?
Microstriae
• Common after post myopic LASIK
• Mismatch of flap to underlying stromal bed
• Folds in Bowman layer
• Gutter typically symmetric
• "Dried cracked mud”
Treatment: observation
Macrostriae
• Local areas of flap slippage/dislocation
• Involves entire flap thickness
• Associated with wider flap gutter
• "Wrinkles in skewed carpet”
Treatment: reflat flap immediately +/- stretch flap
129
What is the most common type of cataract in galactosemia?
• Bilateral oil droplet cataracts
• Develop bilateral cataracts within few weeks of birth
130
What is the most common cause of sunflower cataract?
• Intraocular foreign body made of copper (chalcosis)
• Abnormal copper metabolism (Wilson's disease),
Primary biliary cirrhosis, etc
131
What can cause Christmas tree cataracts?
• Myotonic dystrophy
• Hypoparathyroidism
132
What type of excimer laser is most likely to produce central islands?
• Broad beam lasers
• Central islands = elevation of cornea more than 1D
steeper than surrounding cornea and greater than 1
mm in diameter
133
What are the ocular findings of Weill-Marchesani syndrome and how is it treated?
• Associated with microspherophakia → causes
pupillary block angle closure glaucoma
Treatment:
• Cycloplegics which pull lens-iris diaphragm
posteriorly, decrease anteroposterior lens diameter,
relieve pupillary block
• LPI to prevent angle closure attacks
134
What is the type of higher order aberration caused with decentered ablation?
• Coma
135
What are the potential complications of mitomycin C use in refractive surgeries?
• Destruction of limbal stem cells
• Endothelial cell loss
• Scleral melt
• Failure to re-epithelialize
136
What can Mitomycin C can help prevent in refractive surgery?
• Corneal haze
137
What is a morgagnian cataract?
• Nucleus becomes mobile and sinks to the bottom of
the capsule
• Leads to phacolytic glaucoma
138
What is a hypermature cataract?
• Part of the cortex of a mature cataract starts to
liquefy and leak through the lens capsule
• Gives lens capsule a shrunken appearance
• Leads to phacolytic glaucoma
139
What is an intumescent cataract?
• Cataract swells secondary to taking up abundant
amount of water
140
What is a cerulean cataract?
• Small bluish opacities located in lens cortex that do
not typically cause visual disability
• A type of autosomal dominant congenital cataract
and occasionally found in Down syndrome
141
What are the common changes in lens fibers that occur with age?
• Proteins progressively become more water insoluble
(scatter light)
• Lens protein aggregation and cross-linking 🡪
protein-to-protein and protein-to-glutathione
disulfide bond formation 🡪 accelerated by oxidative
damage
• Glutathione is major molecule that promotes
reducing environment
142
What factors can increase the risk of prolonged inflammation after cataract surgery?
● Intraoperative reasons:
○ Iris prolapse
○ Iris manipulation
○ Vitreous prolapse/incarceration into wounds
○ Retained lens fragments
○ Intraocular lens malposition
● Other reasons:
○ Children
○ Diabetes
○ Previous intraocular surgery
○ PXF
○ PDS
○ Long term miotic use
143
What is temporal (pseudophakic) dysphotopsias?
• Subjective distortion of temporal VF only after cataract surgery
• Positive dysphotopsias: halo, staburt, flash, streaks of light
• Negative dysphotopsias: shadows (more difficult to tolerate)
• More common in IOL with square-edged design and high-index
material
• Reported in 10-20% of cataract surgery patients
• Many patients will eventually neuroadapt
Treatment:
• If mainly at night → brimonidine or pilo for pupillary construction
• Glasses with thicker frames (coincide with areas of negative
dysphotopsia)
• Reverse optic capture → optic of lens above anterior capsulorrhexis
• Piggyback lens
• Nasal anterior capsule removal with YAG
• Last resort → IOL exchange (lower index IOL with rounded edge)
Way to prevent:
• Lower index lens with rounded edge
• Capsulorhexis rim overlaps lens edge
• IOL well centered
• Optic-haptic junctions horizontally (3 and 9 o'clock)
144
What is the risk of RD after YAG capsulotomy?
● 0.1% to 3.6%
● Half of these RDs occur within 1 year of capsulotomy
● Risk factors and hazard ratios:
○ Axial length > 25 mm → 11.1
○ Vitreous complication (during surgery) → 4.4
○ Male sex → 3.61
145
What is the congenital cataract 1/3 rule?
• 1/3 systemic disease/illness
• 1/3 inherited with minimal effects on vision
• 1/3 undetermined causes
146
What are the increased risks in pseudoexfoliation syndrome during and after cataract surgery?
• Accelerated PCO
• Intraoperative mitosis, vitreous loss, floppy iris, iris
prolapse
• Dislocation of IOL due to zonular dehiscence
147
What is the thickness of the lens capsule?
148
What part of the lens capsule is responsible for the production of new lens fibers?
• The outer edge of epithelial layer at lens equator
(lens bow)
149
What are the characteristics of the lens capsule epithelium?
• Anterior capsule has a monolayer of lens epithelial
cells
• No epithelium is associated with the posterior
capsule
150
What is a posterior subcapsular cataract?
• Epithelial disparage at lens equator followed by
posterior migration of lens epithelial cells along
posterior capsule
• Cells migrate to center of posterior capsule and
enlarge 5-6 times normal size
• Swollen cells are called bladder or Wedl cells
• Situations that cause pupillary enlargement
(distance vision, night vision, dilating drops) improve
vision
• Situations causing pupillary constriction (bright
lighting) worsen vision due to light forced to go
through central posterior opacification
151
How does silicone oil complicate lens selection?
• Obtaining measurement ultrasonic biometer can be
unreliable, given different ultrasound velocity for
silicone oil (980 m/s) and vitreous (1532 m/s)
• Silicone creates a negative lens power in the eye
when coupled with biconvex IOL, increasing IOL
power by 3-5 diopters in order to avoid hyperopic
surprise
• AVOID silicone lens
152
What do you do to decrease movement of a contact lens on the cornea?
• Steepening (decreasing) base curve
• Increasing diameter of CL
153
What do you do to increase movement of a contact lens on the cornea?
• Flattening (increasing) the base curve
• Decrease diameter of lens
154
What are the low order wavefront aberrations?
• Positive defocus: myopia
• Negative defocus: hyperopia
• Regular astigmatism produces a wavefront
aberration that has orthogonal and oblique
components
155
What is coma?
• Coma is a 3rd order aberration
• Occurs when rays at one edge of pupil converge
before ray at opposite edge of pupil
• occurs in decentered ablations correctable with RGP
and wavefront-guided keratorefractive surgery
156
What is trefoil?
• Trefoil is a 3rd order aberration
• Can occur after refractive surgery and produces less
degradation in image quality than does coma
• Correctable with RGP and wavefront-guided
keratorefractive surgery
157
What is spherical aberration?
• Spherical aberration is a 4th order aberration
• Occurs when peripheral light rays impacting a lens or
the cornea focus in front of more central rays
• Correctable with RGP and wavefront-guided
keratorefractive surgery
158
What is Peters type 1 and what are the implicated genes?
• Iridocorneal adhesion
• PITX2, FOXC1, CYPB1, PAX6
159
What is Peters type 2?
• Lens touch to area of vascularized corneal opacity
• Failure of lens vesicle to separate from surface
ectoderm
• FOXE3
160
What is Peters plus syndrome?
• Peters anomaly with systemic defects - congenital
brain defect, heart defect, craniofacial anomalies
