Devlin: Refractive Sx Flashcards
What are the true goals of refractive surgery?
- Reduce dependence on glasses
- CL intolerant
- Ideal for 20-40 yo
What is the general concept for refractive sx?
Reshapes cornea to create proper focus
What changes to the cornea are made for myopes?
Laser flattens cornea
What changes to the cornea are made to hyperopes?
Laser steepens cornea
What changes are made to the cornea for astigmats?
Laser sphericalizes the cornea
Name the surgical option no longer performed. What was the bad long-term effect of it?
Radial Keratotomy (RK)
- find progressive hyperopia (central flattening) as long-term effect
What are the 3 types of surface ablation methods?
- PRK
- LASEK
- Epi-LASEK
What are the 2 types of corneal remolding techniques?
Surface Ablation
LASIK
Refractive sx can be divided into what 2 parts?
- exposing tissue to be ablated
2. ablating the tissue
What does PRK stand for?
PhotoRefractive Keratectomy
Is the epithelium preserved in PRK?
No
What are the 3 complications of PRK?
- Anterior Stromal Scarring
- Delay in healing
- Best VA is 6 wks post op
How is the epithelium removed during PRK?
Removal of epithelium via blade/brush
How is the epithelium loosened in LASEK?
Epithelium loosened w/ denatured alcohol
When compared to PRK and LASEK, epi-LASIK has what type of performance?
Superior performance and results
Where is the epithelium cleaved in Epi-LASIK?
Cleaved at Bowman’s membrane
Where does the epithelium attach to if BM is removed?
Attaches to anterior stroma
What is used to help healing time in an Epi-Lasik patient?
Bandage CLs
When does visual recovery occur in Epi-lasik patients?
4-6 wks
Which procedure was the major breakthrough in kerato-refractive surgery?
LASIK
Where is the corneal flap made in LASIK? What is the purpose of this?
- corneal flap created in anterior stroma
- preserving epithelium, increasing speed of recovery
When is visual recovery in a LASIK patient?
12 hours
What was the original flap creation device?
Mechanical Microkeratome
What is a disadvantage of the Femtosecond Laser used to burn a flap layer instead of cutting?
Heat generated from laser creates Opaque Bubble Layer (OBL)
What tool is used in all 4 corneal reshaping surgical methods?
Excimer Laser - sculpts corneal stroma with microablations to generate new curve
What are the FDA guidelines for Myopia vs. Devlin’s ?
FDA = up to - 14D Dev = up to - 8D
What are the FDA guidelines for Hyperopia vs. Devlin’s ?
FDA = up to + 6D Dev = up to +3D
What are the FDA guidelines for Astigmatism vs. Devlin’s ?
FDA = up to 6D Dev = up to 4D
T or F: the lower the dioptic value, the more likely for success?
True
How much stromal tissue is removed per diopter of correction?
10-15um
What is the K-value change for myopia?
1Drefractive = 1D K-value flattening
What is the K-value change for hyperopia?
1D refrac = 1.2D K-value steepening
What are the 3 types of excimer lasers?
- Broadbeam (worse)
- Scanning Slit (smooth)
- Flying spot (accurate)
What is the goal of wavefront guided lasik?
To eliminate higher order aberration from the cornea
What is the reality of wavefront guided lasik?
Failure lies in the lack of intra-surgical measuring
What are the 2 most common and effective surgeries today?
LASIK & Epi-LASIK
What 3 main tests need to be performed prior to sx?
- Refraction (dry &wet)
- Topography
- Pachymetry
What pachymetry reading is the “cutoff”
< 500um
The FDA requires how much residual stromal bed to be left over after sx?
250um
If a -5D myope pt has 550um cornea and needs a 130 um flap, what is the residual stromal bed?
550 - (130+15um(5)) = 345um
What are the most critical factors affecting candidacy?
- Corneal Topography
- Corneal Pachs
- Spec Rx w/in limits
What is the single biggest candidacy debate in refractive sx?
Topography
What is a major topography sublinical signs of complication?
Forme Fruste keratoconus (FFKC)
What is the #1 king-term risk of corneal refractive surgery?
Ectasia (keratoconus/globus/PMD)
What are systemic conditions that are a possible contraindication to sx?
- Auto-Immune Diseases
- Atopic disease (linked to ectasia)
- Eye rubbing (leads to ectasia)
- Diabetes
What is a successful VA in refractive sx patients?
20/40 or better
Who has the higher regression rate after sx? myopes or hyperopes?
Hyperopes, more likely to need enhancement
What are the 3 types of intraoperative risks?
- Free cap
- Buttonhole/Thin flap
- Decentered ablation
- Under/Over Correction
Describe a free cap?
Microkeratome makes complete pass and entire cornea flap comes off
Describe buttonhold/thin flap?
Suction loss causin incomplete flap
Describe Decentered Ablatin?
Pt not positioned properly, not cooperative, results in irregular topography
Describe under/over correction?
Refraction error due to corneal hydration issue
What are the post-operative risks?
- Stria
- Epithelial Ingrowth
- DLK
What do stria occur from?
Eye rubbing or naturally during flap dehydration
What 2 ways can stria be dealt with?
- Massaged out with Weck-Cel sponge
2. Lift flap, smooth, hydrate, replace
What % of LASIK patients get epithelial ingrowth?
1-2%
How can one prevent epithelial ingrowth?
Align flap perfection on replacement
How can we tx epithelial ingrowths?
Lift flap and clean; mitomycin C use is debated
What is Diffuse Lamellar Keratitis?
Active inflammation within the interface
starts in periphery and migrates toward visual axis
When does DLK occur?
1-7 days post op
How do we tx DLK?
- Pred Forte q1h
- Meldrol Dose Pak
- Surgeon lift flap, clean and apply steroids
The Visian ICL is only for what type of refractive error? How many diopters? Is it reversible?
Myopic (-3D to -16D)
Reversible
How large must one’s AC depth be for an ICL? How many endothelial cells?
> 3.000
>3,000 cell count
What are the 3 main risks associated with the Visian ICL?
- Cataract formation
- Endothelial Cell loss
- Glaucoma - pupillary block or angle closure
What type of refractive error does the Verisyse-Artisan lens correct for?
Myopia, Hyperopia, Astigmatism
What are the 2 risks of Verisyse-Artisan lens?
- Endothelial cell loss
2. Glaucoma - pigment dispersion or narrow angle
