Refractive surgery techniques

Question 1

Name an old refractive surgery technique that you could still see in practice

Answer 1

Anterior radial keratotomy

Question 2

what is anterior radial keratotomy?

Answer 2

where 2 to 24 radial incisions are made to flatten the cornea to reduce myopia

Question 3

what are the intraoperative and post op complications of anterior radial keratotomy?

Answer 3

intra op:
*Cuts too close to limbus can trigger neovasc
*Marking errors
*Optical zone invasion
*corneal perforation

post op:
*under/ over correction
*Early regression
*Later hypermetropic drift
*Pain and glare
*Stromal melt
*Corneal perforation following minor *trauma

Question 4

What are the advantages of laser refractive surgery?

Answer 4

*Monochromatic (one wavelength) so *targets specific tissue
*Coherent and minimal divergence
*All waves/ photons are in phase
*Intense and can be focused
*Can be quickly switched on and off

Question 5

what is argon fluoride excimer laser used for and how does it work?

Answer 5

laser used in refractive surgery
- Peptide bonds linking collagen in the cornea absorb the energy from the laser, causing then to break in photoablative decomposition and allows for minimal thermal damage to adjacent tissue
(wavelength 193nm)

Question 6

What does PRK stand for and what’s the procedure?

Answer 6

photorefractive keratometry
-Anaesthetise cornea
-Remove epithelium mechanically or using alcohol
-Fire the laser aiming for initial over correction to anticipate for some regression

Question 7

what is post op management for PRK?

Answer 7

-Analgesics for up to a week
-Antibiotic for a few days until epithelium has healed
-Ocular lubricants for at least 1 month
-Anti inflammatory tapered over 3 to 6 months
-Often need bandage contact lens

Question 8

what are complications for PRK?

Answer 8

-pain/ photophobia
-Blurred vision
-Haze due to non-transparent myofibroblast formation
-Regression which could be due to epithelial hyperplasia in small optic zones with steep edges or regrowth of the stroma in large, well blended treatment zones
-Usually starts first 2-4 weeks, peaks 2-3 months and then gradually fades
-Under over correction
Impaired CS
-Increased ocular aberrations
-Reduced best corrected VA
-Night vision difficulties due to glare from increased aberrations

Question 9

What does LASIK stand for and what is the procedure?

Answer 9

Laser in situ keratomileusis

1. IOP is raised to over 65 with a suction ring placed around the limbus to stop the cornea from wobbling during the procedure
2. Surgical cut is made with oscillating blade
3. Creates a flap
4. Intrastromal ablation (corneal epithelium is left intact)
5. flap is replaced

Question 10

how many people do night vision difficulties post PRK affect?

Answer 10

Affects everyone immediately after surgery
25% 1 month post op
Reduced to 5% after 1 year

Question 11

How does LASIK compare to PRK?

Answer 11

LASIK is:
Less epithelial insult
Less pain
Quicker recovery
Less haze and regression

Question 12

what is LASIK post op management

Answer 12

Antibiotic - 1 week
Ocular lubricants for at least 1 month
Anti inflammatory tapered over 2 weeks

Question 13

what are the complications of LASIK?

Answer 13

same as PRK plus complications associated with the flap:
-Incomplete flap
-Irregular flap
-Decentred flap
-Microfolds
-Macrofolds
-Dislocation
Last 3 mainly can be caused by rubbing eyes after surgery
Epithelial cell growth in the space beneath the flap

Question 14

in LASIK, how can epithelial cells grow under the flap?

Answer 14

Could be due to fluid back flow during stromal bed irrigation

Could be transferred from the microkeratome used to make the cut

Question 15

why is epithelial cell growth under the flap in LASIK a complication? How can it be managed?

Answer 15

• disrupt clarity of vision
• Usually stable but if they expand, they can block passage of nutrients from aqueous to the flap which can cause proteolytic enzyme release causing flap melt and irregular astigmatism

Management would be to lift the flap back up and scrape away epithelial cells grown

Question 16

what does LASEK stand for and what is the procedure?

Answer 16

Laser subepithelial keratomileusis
1. Diluted alcohol loosens epithelial adhesion
2. Epithelium moved to one side
3. Laser ablation
4. Epithelium returned
(combines LASIK and PRK)

Question 17

What is epi-LASIK?

Answer 17

the same as LASIK only a micokeratome removes the epithelium and preserves Bowman’s membrane (so no flap)

Question 18

What are the advantages of epi-LASIK and LASEK compared to LASIK?

Answer 18

• No flap related complications
• Wavefront calculations not affected by creation of flap
• May be offset by more aggressive wound healing

Question 19

what are the advantages of epi-LASIK and LASEK compared to PRK

Answer 19

Slightly less pain
Quicker visual recovery