Lec 9 Corneal Surgery

Question 1

What’s the 5 corneal refractive procedures

Answer 1

LASIK

PRK

LASEK/EPI-LASEK (variation of PRK)

RK

Question 2

What surgeries are for corneal disease management

Answer 2

Corneal cross linking

PKP (Penetrating Keratoplasty)

Question 3

What to consider pre and post operation of surgery

Answer 3

Pre:
refraction status/target
corneal status

Post:
immediate therapeutic needs
Corneal integrity and shape
Residual optical needs

Question 4

How can CL help before surgery

Answer 4

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

Question 5

Before corneal refractive surgery what do you need to do

Answer 5

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

Question 6

What happens in LASIK

Answer 6

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

Question 7

Benefits of laser tissue removal within the cornea WHILE MAINTAINING an intact epithelium

Answer 7

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

Question 8

Complications that can occur in LASIK

Answer 8

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

Question 9

Random other post surgical complications

Answer 9

Dry eye, glare and haloes

Regression/under/over correction

Induction of regular/irregular astig And monocular diplopia

Loss of BCVA

Question 10

Post LASIK management involving CL
Optical correction
Flap damage or relift required

Answer 10

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

Question 11

What’s PRK

Answer 11

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

Question 12

Benefits of PRK

Answer 12

Low risk for ectasia as laser applied higher in cornea

Quicker as fast to remove epithelium

No flap related complications

Question 13

Complications of PRK

Answer 13

Risk for stromal haze as epithelium not intact

Risk for scar formation during regrowth

Risk for infection with exposed cornea

Question 14

Therapeutic Management of PRK with CLs

Answer 14

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

Question 15

Optical management of PRK

Answer 15

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

Question 16

What’s LASEK

Answer 16

Cross between PRK and LASIK

Epithelial flap is made with alcohol loosening the epithelial adhesion

Once laser applied the flap is put back over

Question 17

What’s Epi-Lasik

Answer 17

Same as LASEK but instead of alcohol Epi-lasik uses a blunt blade

Question 18

Difference between LASEK and PRK

Answer 18

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

Question 19

What’s Radial Keratotomy

Answer 19

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

Question 20

What’s bad about RK

Answer 20

Hyperopic shift

Saggy corneas

Diurnal fluctuations

Question 21

Management of RK

Answer 21

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

Question 22

Describe corneal cross linking

Answer 22

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

Question 23

Who is corneal cross linking for and when is it not used

Answer 23

Progressive keratoconus/pellucid marginal degeneration

Iatrogenic keratectsia

Infectious ulcer and edematous bullous keratopathy as UV kill infection

BUT need minimum thickness 400um

Question 24

Management of corneal cross linking

Answer 24

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

Question 25

What’s penetrating Keratoplasty

Answer 25

Full thickness corneal transplant Where donor cornea is sutured in

Question 26

When to do PKP

Answer 26

Advanced keratoconus

Trauma

Corneal scar and opacity

Bullous keratopathy

Prev failed graft

Question 27

Challenges with PKP

Answer 27

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

Question 28

Management of PKP

Answer 28

Large lenses to fit over graft junction

Avoid tight fits and risking neovasc or inducing mechanical pressure