Intro to Refractive & Cataract Surgery Flashcards
the cornea has how much power in diopters? the lens?
cornea = 40.00 D lens = 20.00 D
corneal refractive surgery changes what?
corneal curvature
when treating myopia with refractive surgery, what do you do to the cornea?
flatten the central cornea
when treating hyperopia with refractive surgery, what do you do to the cornea?
steepen the central cornea
what is the process called when you sculpt the cornea?
keratomileusis
what is a parallel faced corneal disc?
microkeratome
what refractive procedure was an accidental finding that used radial cuts to flatten the cornea?
radial keratotomy (RK)
what is the procedure called when you cut & freeze ~300μm layer, reshape it using a lathe, then corneal disc is sutured back onto the eye?
keratomileusis
in radial keratotomy, multiple radial cuts are made where? what does it do?
peripheral corneal stroma → relaxes cornea & causing flattening of cornea
which refractive procedure is used to correct mild to moderate myopia?
radial keratotomy
why is radial keratotomy no longer popular or the safest option?
- corneal integrity is compromised
- instability of refractive results (hyperopic shifts over time & Rx changes w/ diurnal IOP)
which refractive procedure is also known as limbal relaxing incisions & used to correcting astigmatism?
arcuate keratotomy (AK)
in arcuate keratotomy, LRI incisions are made where?
at the steeper axis
what procedure uses two PMMA semicircular ring segments designed to be surgically inserted into deep corneal stroma to flatten the central cornea?
intacs (aka instrastromal corneal ring segments - ICRS)
intacs correct for what refractive error?
mild myopia
intacs are now used as treatment for what? what does it do?
mild to moderate keratoconus → provides structural support for the cone
what refractive procedure uses high frequency radio waves to steepen the cornea?
conductive keratoplasty (CK)
conductive keratotomy corrects what refractive errors?
hyperopia, astigmatism, presbyopia
conductive keratotomy induces what? what does that do?
a retraction in corneal collagen cells → steepens central cornea
conductive keratotomy corrects up to how many diopters of hyperopia?
+3.00 D
what uses reactive gases (eg, chlorine & fluorine) when electrically excited to emits UV light which can make very precise minute changes to biological tissue
excimer laser (IBM)
what refractive procedure used excimer lasers & was a a precursor to LASIK?
photorefractive keratectomy (PRK)
in PRK, what is applied to the cornea to dissolve the epithelial layer?
diluted alchohol solution
in PRK, the excimer laser sculpts which corneal structure to correct refractive error?
stromal tissue
in PRK, after the laser corrects the refractive error, what is used to protect the eye?
antibiotic protective bandage lens is placed over eye
what is used in PRK to reduce risk of PRK haze? where is it applied to? what refractive error is it used for?
mitomycin-C (MMC) – anti-metabolite
- applied to stromal bed
- used in high myopic corrections
PRK is indicated for correction of how much myopia? astigmatism? hyperopia?
≤ -12.00 D of myopia
≤ -4.00 D of astigmatism
≤ +5.00 D of hyperopia
what is considered a stable manifest refraction for PRK?
less than or equal to 0.50D change w/in the last 1-2 years
is PRK or LASIK recommended for thin corneas?
PRK
is PRK or LASIK recommended for dry eye patients?
PRK
is PRK or LASIK recommended for combat/contact sports
PRK
what refractive procedure can be used for LASIK enhancement?
PRK
what procedure is used for corneal scars or degenerations such as EBMD?
phototherapeutic keratectomy
in PRK, how long is the bandage CL left in place?
3-7 days
when do the “seams” of epithelium meet after PRK?
~3rd-4th day
when are bandage CLs removed after PRK? what is used to remove it?
~3rd-5th day gently with forceps
topical steroids are used for how long after PRK? why?
~1-3 months
to reduce haze & decrease chance of scar formation in the stroma
topical antibiotics are used for how long after PRK?
for 1 week
what refractive procedure is a combination of microkeratome & excimer laser?
LASIK
what is the older method of creating flaps in LASIK?
microkeratome
what is the newer method to create flaps in LASIK?
femtosecond laser
modern LASIK uses what?
both femtosecond & excimer lasers
why must use of contact lenses be stopped before LASIK or PRK?
CLs will distort the cornea
how long do you have to de-adapt with spherical contact lenses?
3 days - 1 week
how long do you have to de-adapt with toric CLs?
1-3 weeks
how long do you have to de-adapt with gas permeable contacts?
1 month per decade
can someone with an uncontrolled systemic or autoimmune condition be a candidate for LASIK/PRK?
no
can someone with dry eyes that haven’t been treated be a candidate for LASIK/PRK?
no
if someone has no ocular pathology, are they a good candidate for LASIK/PRK?
yes
what procedures must be done pre-op for LASIK/PRK?
- cycloplegic refraction
- DFE
at least how many microns must be left in the residual stromal bed according to FDA guidelines? most surgeons prefer how many microns? why?
- FDA → at least 250 microns
- surgeons → prefer to stay above 300 to reduce risk of ectasia
in cortical cataracts, if the spokes are in the visual axis, what will occur?
monocular diplopia
in posterior subcapsular cataracts, why are there significant symptoms despite a mild presentation?
posterior capsule is an optical nodal point
why must you document if a patient is diabetic prior to cataract surgery?
diabetics are prone to macular edema
why do you have to observe for blepharitis prior to cataract surgery?
bacterial infection of S. aureus → don’t want it to cause endophthalmitis
why is it important to note any dystrophies or degenerations prior to cataract surgery?
RCEs can occur after surgery
why is it important to note if there is pseudoexfoliation prior to cataract surgery?
iris sphincter won’t work as well → can’t dilate as well (which is what the surgery needs)
why do you check for Seidel’s sign post-op for cataract surgery?
to check to leakage of aqueous humor in the anterior chamber
