Week 2.11 Refractive Surgery Flashcards
What are the two types of refractive surgery
Corneal refractive surgery
Intraocular refractive surgery
Types of corneal refractive surgeries
- LASIK
- LASEK
- Epi-LASIK
- sub bowman’s keratomileusis
- laser thermokertoplasty
- radial keratotomy
- arcuate keratotomy
- corneal injury
- infrastromal
Types of Intraocular refractive surgeries
- phakic IOL
- cataract surgery
- monofocal
- multifocal
- accomodating
- clear lens extraction
What was the first refractive surgery
Radial keratotomy
How does radial keratotomy work
Radial cuts through 95% of corneal thickness using diamond blade
Number of incisions depends on degree of correction required
What are the issues with RK
- hyperopic shift over time
- reduced ocular integrity
- permanent risk of incision keratitis
- poor quality from scars and increased aberrations
Myopic ablations
Aim to flatten cornea (remove tissue centrally) to reduce power of refracting surface
Hyperopic ablations
Tissue removed mid-periphery, steepen the cornea and increase power of the eye
What was the first type of laser refractive surgery
PRK
How does PRK work
Epithelium removed using blade and thrown away
Stroma doesn’t grow back so we can reshape cornea by reshaping stroma
Epithelium regrows
Bandage cls on top
What is the outcome of PRK
Hyperopia and blurry vision during first month
Can take 6-12 months for RX to stabilise
Risk of haze and regression initially
LASEK/EPILASIK
- epithelium not rhown away
- loosened and moved to one side
- laser underlying stroma
- own epithelium flopped back on top
- epithelium acts as a natural bandage CL
How is epi lasik different
Tries to keep epithelium alive
What’s the outcome for LASEK
Epithelial disruption so pain and photophobia
By 1 month good BCVA
By 3 months rx stabilised?
6 months stabilised, CS returned to preop
LASIK
Corneal flap cut - stoma, basement membrane and epithelium
Femtosecond laser used
Underlying stroma ablated and flap repositioned
Femtosecond lasers
- Most common means of flap creation
- Create very small air bubbles close together they join up and are sliced
- Also used in cataract surgery to create incision
What’s the most to least popular treatment
LASIK then LASEK then epiLASIK
Due to speed of recover
LASIK outcomes
3 months - flap scar visible , rx may have stabilised
6 months rx stabilised
Long term - myopic shift?
What’s keratectasia
- Means cornea is weakened and starts bulging forward
- Anterior portion of stroma is denser and stronger than the posterior portion but that the flap does not add to integrity of globe after surgery
- Appears to occur between 1 week and 3 years after surgery – usually LASIK
What levels of ametropia do LASEK & LASIK treat up to
LASEK -8.00DS to +4.00
LASIK -8.00DS to +4.00
Astigmatism ~3.00DC
Phakic IOL for >-7.00DS and +4.00DS
By how much can the IOP be underestimated by after surgery
~0.5mmHg after surgery
E.g. -4D myopia, underestimates IOP by ~2mmHg
What are the two major Intraocular procedures
PIOL - phakic IOL
- additional lens is inserted
“Contact lens inside your eyes” tell px
CLE + IOL
- clear lens extraction and IOL insertion
Basically cataract surgery in absence of cataract
What’s the advantages of IOL procedure
- Corneal profile and clarity remain unchanged
o So little or no increase in scatter or aberrations - Most procedures are reversible or repeatable
- Higher range of refractive error can be treated
- Correction is closer to nodal point of eye, therefore better optics results
Disadvantages of IOL procedures
- More invasive
- Requires greater surgical skill
- Requires sterile environment which can be expensive
- Some IOL lenses have small optic zones
o So may be risk of glare/halos in younger px with larger pupils - Risk of infection is more serious
- There are some serious side effects
o Cataract (IOL)
o Glaucoma
Is phakic IOL reversible?
Yes
Phakic IOL
- Maintains accomodation so younger px usually have this done
- Most useful for high myopes and hyperopes under 40
- Putting a lens in front of your existing lens
