Refractive Surgery Flashcards by Beth Wilkinson

Why do pxs opt for refractive surgery?

Trust modern, expensive technology
Convenience of no specs or CLs
Marketing
Perceived permanence

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Why would pxs not opt for refractive surgery?

Pain
Fear of surgery
Fear of going blind
Having to be awake during the procedure/worry about moving during
Smell of their own eye burning under the laser
Like wearing specs

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How is lamellar keratoplasty performed?

Cornea frozen and flap made
Disc of cornea cut away
Flap replaced

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How is keratophakia performed?

Flap made in cornea
Plastic lens inserted
Flap replaced

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How is epikeratoplasty/phakia performed?

Corneal epithelium removed
Groove cut
Lens sutured to cornea as a ‘living CL’

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How do intrastromal corneal ring segments work?

2 PMMA semi-circular inserts go into intrastromal channels, which flatten the cornea

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How does anterior radial keratotomy work?

Radial incisions are made in the cornea to flatten the cornea

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How does photocoagulation work?

Proteins are denatured due to the heat caused by molecular vibrations

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How does photodisruption work?

Light strips electrons from atoms, creating a plasma and then a shockwave which dissociates molecular bonds

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How does argon-fluoride excimer laser work?

Photodisruption: collagen peptide bonds (chromophores) broken with some adjacent heat damage

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How is PRK performed?

Epithelium is removed
Excess moisture removed
Laser fired at central cornea

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How is LASIK performed?

Flap created
Intrastromal cornea ablated
Flap replaced
(Epithelium and Bowman’s membrane in tact)

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How is LASEK performed?

Diluted alcohol loosens epithelial adhesions
Epithelium moved to the side
Cornea ablated
Epithelium returned

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What factors have a larger effect in anterior radial keratotomy?

More incisions
Deeper incisions
Steeper corneal curvature
Larger corneal diameter
More rigid cornea
Older px
Higher IOP

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What is a disadvantage of anterior radial keratotomy?

Unpredictable due to many variables

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What are some intraoperative complications of anterior radial keratotomy?

Marking errors
Invasion of optical zone (causes glare and irregular astigmatism)
Incision made beyond the cornea (if close to limbus, neovasc risk increases)
Corneal perforation (small will heal)
Intersecting incisions

What can help to reduce risk of intraoperative complications during anterior radial keratotomy?

Real-time pachymetry

What are some post-operative complications for anterior radial keratotomy?

Under/overcorrection
Early regression
Late hyperopic drift
Pain and glare (reduce with time)
Diurnal variation due to IOP
Irregular astigmatism
Infection
Stromal melt
Corneal perforation after minor trauma

What % of anterior radial keratotomy pxs achieved 6/6 and 6/12 after 10 years?

6/6: 53%
6/12: 85%

What does LASER stand for?

Light Amplification by Stimulated Emission of Radiation

What are the advantages of laser techniques in refractive surgery?

Monochromatic wavelength: can target specific tissues
Waves/photons are in phase: beam is intense and can be focused
Can be quickly switched on and off
All above allow for precision

What are some examples of photodisruption?

YAG capsulotomy
Argon-fluoride excimer laser

What is the wavelength of an Argon-Fluoride Excimer Laser?

193nm

How much tissue is removed per pulse with an Argon-Fluoride Excimer Laser?

0.21-0.27um

What surgeries are performed using a Argon-Fluoride Excimer Laser?

PRK LASIK LASEK

What is aimed for during PRK and why?

Overcorrection due to anticipated regression

What is the post operative care for PRK?

Anaesthetic for up to a week Antibiotic for a few days (until epithelium healed) Ocular lubricants for 1 month Anti-inflam for 3-6 months Bandage CL (not all cases)

What are the surgical complications of PRK that are due to epithelium removal?

Pain Photophobia Blurred vision Haze

What are the surgical complications of PRK that are due to regression?

Stromal regrowth in large well-blended treatment zones Epithelial hyperplasia in small optic zones with steep edges

When do the surgical complications of PRK that are due to epithelium removal occur and peak?

Starts 2-4 weeks Peaks 2-3 months

What are the visual complications of PRK?

Under/overcorrection Regression Impaired CS (3-6 months) Increased ocular abberations Reduced VA Night vision difficulties due to glare (increased scatter and abberations), reduced CS.

Why is LASIK better than PRK?

Less epithelial insult Less pain Faster recovery Less haze, regression and photophobia

What is the post operative care for LASIK?

Antibiotics for 1 week Ocular lubricants for 1 month Anti-inflam for 2 weeks

What are the post-op complications of LASIK?

Same as PRK plus: Flap creation complications (incomplete, free, buttonhole, irregular, decentred) Corneal perforation Flap related after creation (microfolds, macrofolds, wrinkling, dislocation) Interface inflam (cells under flap, need to be scraped)

What is Epi-LASIK?

Epithelium is removed but Bowman's membrane is preserved

What are the advantages of LASEK and Epi-LASIK?

No flap related complications Wavefront calculations aren't affected by flap creation Less pain/haze and quicker visual recovery than PRK

What are some future options?

Phakic Intra Ocular Lenses (pIOL) - iris fixed or posterior chamber