Refractive Surgery Flashcards
Radial Keratotomy
RK
uses diamond blade to make radial cuts deep into cornea to flatten it
RK was used to treat….
myopia
Problems with RK
permanently weakened cornea unpredictable results vision fluctuation starbursts not used
Astigmatic Keratotomy
AK
arcing parallel cuts in periphery- steepen flatter and flatten steeper
often done during cataract surgery
AK is used to treat….
high post-keratoplasty astigmatism
small degrees of pre-existing astigmatism
Non- Contact Holmium uses…..
YAG laser
induces heat
Non- Contact Holmium
places shrinkage spots outside visual axis to steepen cornea
Non- Contact Holmium was used to treat….
hyperopia
Problems with Non- Contact Holmium
induces astigmatism
high regression rate
not used anymore
Conductive Keratoplasty
CK
radio frequency delivered to stroma by probe
predictable, safe, cheap
Conductive Keratoplasty Use
low levels of hyperopia and presbyopia
Contraindications for CK
pacemakers
CK and Monovision
used on one eye so one for distance and one for near
Laser Photoablation uses….
argon- fluoride gas
Photorefractive Keratectomy
PRK
corneal epithelium removed
excimer laser photoablates anterior stroma to flatten or steepen cornea
Indications of PRK
+3 to -6; -8 w/ mitomycin C
cornea too thin for LASIK
residual refractive error after cataract or refractive surgery
epithelial irregularities, EBMD, K scars
Problems with PRK
significant postop discomfort- 2-3 days
slow vision recovery
subepithelial haze-more permanent with higher powers
Mitomycin C
helps decrease haze in PRK
can cause corneal toxicity
Laser in situ Keratomileusis
LASIK
flap created with microkeratome blade or femtosecond laser
photoablation in deep stroma
flap repositioned over ablated area
Benefits of LASIK
deep stromal ablation results in less haze no pain (epithelium intact) and almost instant vision
Indications for LASIK
those prone to haze- -6D or more; significant astig
wanting immediate visual recovery
cant handle pain
Problems with LASIK
loud clicking and burning smell from gas (not burning)
flap complications
epithelial growth under flap
corneal ectasia if cut too thin
Contraindications of LASIK
epithelial irregularities- EBMD and scars
Thickness required for LASIK
250 micrometers remaining of stroma
100 for flap
12 x each D
added cannot be greater than central corneal thickness
Laser Subepithelial Keratectomy
LASEK
alcohol loosens epithelium, which is folded back for photoablation and rolled back after
like PRK but faster recovery and less discomfort
Epithelium in LASEK
most dies as a result of alcohol
Epithelial Laser in situ Keratomileusis
epi-LASIK
like LASEK but flap made with microeratome- less epithelial toxicity and more viable
Best refractive surgery for <6D of myopia
PRK
Best refractive surgery for 6 - 10D of myopia
LASIK
less risk of haze
Phakic Intraocular Lenses
artifcial lenses inserted into eye to correct higher refractive error
placed in anterior or posterior chamber
Artisan Lenses
pIOL clipped on to front of iris
Advantages of pIOL
> 20D of hyperopia or myopia
7.5D of astigmatism
reversible
maintains accommodation
Disadvantages of pIOL
min AC depth of 3.2mm- rules out most hyperopes
endothelial cell loss or cataract formation from rubbing
potential for glaucoma
Refractive Lens Exchange
replaces actual lens with fake one to correct refractive error
Advantages of RLE
spherical corrections +20 to -30D
available in toric, multifocal, accommodating
no need for later cataract surgery
Disadvantages of RLE
loss of accommodation
high myopes at risk of RD
pIOL vs RLE
pIOL safer and better for non-presbyopes
RLE better for high hyperopes w/ shallow AC and those needing cataract surgery soon
CK Post-Op Presentation
FB sensation and tearing
functional vision next day, can go back to work
astigmatism worse in 1st month
effects regress 1D every 2-3 yrs
Mx PRK
repithelialization takes ~3 days- discomfort and lack of functional vision, wear BCL
vision fluctuates until about 6 months
LASIK Post-Op Presentation
no discomfort, good vision in 24 hours
vision stabilizes after 3 months
watch for flap complications