Lec 9 Corneal Surgery Flashcards
What’s the 5 corneal refractive procedures
LASIK
PRK
LASEK/EPI-LASEK (variation of PRK)
RK
What surgeries are for corneal disease management
Corneal cross linking
PKP (Penetrating Keratoplasty)
What to consider pre and post operation of surgery
Pre:
refraction status/target
corneal status
Post:
immediate therapeutic needs
Corneal integrity and shape
Residual optical needs
How can CL help before surgery
Determines target refractive outcome e.g ability to trail mono vision correction vs full distance correction for presbyopes
- check rivalry issues or being able to adapt to CL after Surgery
Before corneal refractive surgery what do you need to do
Stop CL use 1-6 months if RGP VS 1-3wks if SCL
check if they have updated glasses
Preoperation measurements like topography, repeating refraction and checking thickness
What happens in LASIK
Circular flap created using a micro keratome blade/femtosecond laser to expose stroma
UV rays from excised laser applied to remove tissue to change refraction
Flap laid back down
Benefits of laser tissue removal within the cornea WHILE MAINTAINING an intact epithelium
Minimise discomfort after surgery since corneal nerves not exposed
Less refractive fluctuation as treatment in stroma
Less stromal response as tissue doesn’t undergo much of healing response
Complications that can occur in LASIK
Flap damage
Non smooth flap requiring relift and correction
Debris under flap
Epithelial in growth undergo flap requiring relift and scrap removal
Iatrogenic post lasik cornea ectasia
Random other post surgical complications
Dry eye, glare and haloes
Regression/under/over correction
Induction of regular/irregular astig And monocular diplopia
Loss of BCVA
Post LASIK management involving CL
Optical correction
Flap damage or relift required
Optical correction:
- wait 1 month before SCL and 2-4 months before RGP to ensure cornea stabilise
- CL mask surface irregularity better than spectacles
IF Flap damage = soft CL till epithelium healed so few days
IF flap relift = soft CL with good movement for 1-2 days
What’s PRK
Photo Refractive Keratectomy
8-9mm if epithelium removed and then Uv rays from excimer laser applied to remove tissue
Epithelium grows back over 3-5 days
Benefits of PRK
Low risk for ectasia as laser applied higher in cornea
Quicker as fast to remove epithelium
No flap related complications
Complications of PRK
Risk for stromal haze as epithelium not intact
Risk for scar formation during regrowth
Risk for infection with exposed cornea
Therapeutic Management of PRK with CLs
Bandage CL 4-5 days/nights to reduce discomfort and aid healing
Normal blinking encouraged to minimise drying, dislocation or fitting problems
Topical ABs/NSAIDS/Steroids
Lens replacement IF protein or lipid buildup
Optical management of PRK
Rigid lenses to correct corneal irregularity of either:
- reverse geometry lens
- large diameter lens
Note BC needs to be diagnostically cited to tailor the periphery to the presurgical cornea
What’s LASEK
Cross between PRK and LASIK
Epithelial flap is made with alcohol loosening the epithelial adhesion
Once laser applied the flap is put back over
What’s Epi-Lasik
Same as LASEK but instead of alcohol Epi-lasik uses a blunt blade
Difference between LASEK and PRK
Both need CL post operatively to heal epithelium
LASEK takes 1 day longer for epithelium to heal and adhere than for epithelium to regrow in PRK
LASEK has less discomfort
LASEK has less intense wound healing
What’s Radial Keratotomy
Spoke like incisions placed in cornea to flatten shape and reduce myopia and astig - radial lines correct sphere while parallel lines to limbus correct astig
The peripheral corneal bulge allows for central corneal flattening
What’s bad about RK
Hyperopic shift
Saggy corneas
Diurnal fluctuations
Management of RK
RGPS for optical clarity and potential to reach better VA
- flat BOZR, reverse geo design, large lenses for stability
Soft Torics For hyperopic astigmatic refraction BUT get diurnal fluctuation as soft toric won’t fix corneal cyl like in RGP
AND risk neovasc onto incisions
Describe corneal cross linking
7mm epithelium removed and the. Riboflavin drops (photosensitizer) is out in cornea every 3 min for 30 min while exposed to UV
strengthen chemical bonds in stroma
Who is corneal cross linking for and when is it not used
Progressive keratoconus/pellucid marginal degeneration
Iatrogenic keratectsia
Infectious ulcer and edematous bullous keratopathy as UV kill infection
BUT need minimum thickness 400um
Management of corneal cross linking
Bandage soft CL 3-5 days that covers well move a bit and not be too tight
Topical AB till epithelium regrown
Soft CL stopped and then topical steroid used with taper
What’s penetrating Keratoplasty
Full thickness corneal transplant Where donor cornea is sutured in
When to do PKP
Advanced keratoconus
Trauma
Corneal scar and opacity
Bullous keratopathy
Prev failed graft
Challenges with PKP
graft rejection - neovasc
Irregular cornea put on = huge cyl
Apical zone not centred OR Difference in elevation between peripheral and host cornea
Grafts can be diff shaped
Need for long term steroids and sutures that could be permanent
Management of PKP
Large lenses to fit over graft junction
Avoid tight fits and risking neovasc or inducing mechanical pressure
