refractive surgery

Question 1

prevalence of myopia in UK

Answer 1

15-20%

Question 2

complications from radial keratotomy

Answer 2

• glare from incisions
• reduced contrast sensitivity
• diurnal variation
• hyperopic drift
• weakened globe

Question 3

what is radial keratotomy?

Answer 3

cuts in the cornea to flatten the cornea
the amount of cuts depends on the amount of myopia present

Question 4

what does this image show??

Answer 4

radial keratotomy

Question 5

when was laser refractive surgery first suggested?

Answer 5

1980s

Question 6

what was the first use of laser in ophthalmology?

Answer 6

photo-coagulation for DR - 1960s

Question 7

what does this image show?

Answer 7

smooth calcific band keratopathy - LASER CAN GET RI OF SUPERFICIAL SCARS LIKE THIS !!

Question 8

what does -OTOMY mean??

Answer 8

taking tissue away

Question 9

what does PRK stand for?

Answer 9

photo refractive keratectomy

Question 10

limitations of PRK

Answer 10

• INDIVIDUAL WOULD HEALING VARIATION
• small diameter ablation zones
• single pass treatments = aberration
• poor beam homogeneity
• edge-profile sub-optimal

Question 11

what is a small ablation zone?

Answer 11

central 4mm which could be treated (initially - now we can treat the whole cornea)
leaves a haze in the centre

Question 12

what happens if you cannot treat the whole cornea?

Answer 12

positive spherical aberration (HALOS)

Question 13

major complications of PRK

Answer 13

• regression
• anterior stromal haze
• aberrations (halos)
• night vision problems
• loss of BCVA
• loss of contrast sensitivity

Question 14

regression in PRK

Answer 14

start at -10
get PRK
be +4.00 ish
regress back to myopia (roughly -4.00)

Question 15

why was LASIK introduceD?

Answer 15

to stop anterior haze (would be inside the cornea)

Question 16

what does LASIK stand for?

Answer 16

Laser
ASisted
In-situ
Keratomileusis

Question 17

advanatges of LASIK

Answer 17

• virtually no haze or scarring
• rapid recovery
• more accurate/predictable
• extended range (-10 to +5)
• virtually painless
• both eyes treated at same time
• re-treatment is relatively easy

Question 18

how does LASIK work?

Answer 18

• slicer which produces a very thin flap (1/5th the thickness of the cornea)
• flap is lifted
• UV light from the laser (works at 193nm) - PX CANNOT SEE THE BEAM
• px fixates on a flashing red light

Question 19

what is waveScan?

Answer 19

scans the wavefront
tells you if they have any aberrations (sph, cyl, coma etc)

Question 20

when wavescan is scanning, how does it work?

Answer 20

uses a flying spot laser (laser scanning spot)
different sizes

Question 21

what is the aim of WaveScan?

Answer 21

tries to create the perfect cornea shape to get minimum point spread function

Question 22

why is iris registration/recognition v important?

Answer 22

need to line up the cornea properly otherwise you could make their aberrations worse

Question 23

what form of refractive surgery is the gold standard

Answer 23

LASIK

Question 24

when is lasik an NHS treatment?

Answer 24

• myopia after cataract surgery
• treating corneal graft astigmatism
• severe disability (motoneurone disease, parkinsons, stroke patientts, friedreichs ataxia) - UNABLE TO WEAR GLASSES

Question 25

what are the 5 main refractive groups

Answer 25

- simple myopia - astigmatic myopia - hyperopia - astigmatic hyperopia - mixed astigmatism

Question 26

why do you need to analyse YOUR laser results (not just generic from the manual)

Answer 26

need to determine if the laser is under or over correcting your patients

Question 27

if the laser is under or over correcting your patients, what do you do?

Answer 27

need to adjust the laser output e.g. if laser is producing results at 85% of full correction, you need to boost the laser by 15% to get full correctin

Question 28

in a high prescription, do you use LASIK or LASEK?

Answer 28

LASEK

Question 29

what are the factors that need to be assessed of refractive surgical techniques

Answer 29

SAFETY efficacy stability cost predictability

Question 30

pre-operative complications of LASIK

Answer 30

patient selection/suitability patient counselling realistic expectations refractive aims (e.g. monovision)

Question 31

operative complications of LASIK

Answer 31

poor preparations sterility issues equipment related technique related

Question 32

flap complications THERE ARE SOOOOOOOO MANY but not sure we need to know this 100%

Answer 32

- partial flap (obstruction/suction break) - buttonholes + thin flaps (steep corneas) - macerated flap - free flap (cap - flat corneas, low IOP) - no flap (loss of suction) - epithelial defects

Question 33

how does careful preparation and technique avoid flap complication in LASIK?

Answer 33

drapes, good exposure, vacuum good centration, copious irrigation chayet sponge mask hinge (e.g buratto guard)

Question 34

how does repositioning the flap avoid flap complication in LASIK?

Answer 34

vidaurri cannula adequate irrigation align para-radial marks dry edge of flap gently (and wait)

Question 35

why does a macerated flap occur?

Answer 35

due to a faulty blade

Question 36

post-op complications of lasik

Answer 36

- flap macro and micro striae - debris - displaced flaps - corneal surface problems - DRY EYE - DLK - diffuse lamellar keratits - infective keratitis - epithelial ingrowth

Question 37

why do striae occur in LASIK?

Answer 37

meibomian secretions get under the flap

Question 38

what is the most common post-op complication of LASIK?

Answer 38

dry eye disease (30% of px's)

Question 39

what problems does epithelial ingrowth cause?

Answer 39

optical problems melting - keratolysis FB sensation

Question 40

why does dry eye disease occur post LASIK?

Answer 40

damaged corneal nerves cutting back on the positive feedback to the lacrimal gland

Question 41

how do you manage dry eye disease with laser?

Answer 41

pre-op screening/exclusion preservative free tear film supplements punctum plugs sodium hyaluronate cyclosporin A autologous serum

Question 42

what are the residual refractive error and quality of vision complications of LASIK

Answer 42

under or over correction induced cylinder irregular astigmatism halo/glare/ghosting/scatter

Question 43

why would you do LASIK retreatment?

Answer 43

fine tuning

Question 44

what is DLK? diffuse lamellar keratitis

Answer 44

white granular cells in peripheral infiltrate (under the flap)

Question 45

what is corneal ectasia?

Answer 45

we have made the cornea too thin (THINK OF IT LIKE INDUCED KERATOCONUS)

Question 46

who is more likely to get corneal ectasia?

Answer 46

high myopes (ofc) and ppl with thin corneas

Question 47

how do you prevent post-LASIK ectasia?

Answer 47

ensure normal topography flap thickness, pachymetry limit ablation to 80 micron maximum -8.00 D

Question 48

which laser is used to make a corneal flap?

Answer 48

femtosecond photodisruption

Question 49

how does femtosecond photodisruption work?

Answer 49

a pulse of laser energy is focused to a precise location inside the conrea. (1 micron) a microplasma is created vaporizing 1 micron of cornea tissue vaporization creates an expanding bubble of gas & water seperating the corneal lamellae

Question 50

which kinds of px's ar emore likelyto have unrealistic expectations?

Answer 50

IT people architects/surveyors licence applicants night drivers bare questions low myopic presbyopes 30 y/o accompanied by mum px who talk you round to the statistics they would like to hear "but it will be okay for me - wont it??"