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Eye Disease > refractive surgery > Flashcards

refractive surgery Flashcards

1
Q

prevalence of myopia in UK

A

15-20%

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2
Q

complications from radial keratotomy

A
  • glare from incisions
  • reduced contrast sensitivity
  • diurnal variation
  • hyperopic drift
  • weakened globe
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3
Q

what is radial keratotomy?

A

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

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4
Q

what does this image show??

A

radial keratotomy

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5
Q

when was laser refractive surgery first suggested?

A

1980s

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6
Q

what was the first use of laser in ophthalmology?

A

photo-coagulation for DR - 1960s

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7
Q

what does this image show?

A

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

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8
Q

what does -OTOMY mean??

A

taking tissue away

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9
Q

what does PRK stand for?

A

photo refractive keratectomy

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10
Q

limitations of PRK

A
  • INDIVIDUAL WOULD HEALING VARIATION
  • small diameter ablation zones
  • single pass treatments = aberration
  • poor beam homogeneity
  • edge-profile sub-optimal
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11
Q

what is a small ablation zone?

A

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

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12
Q

what happens if you cannot treat the whole cornea?

A

positive spherical aberration (HALOS)

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13
Q

major complications of PRK

A
  • regression
  • anterior stromal haze
  • aberrations (halos)
  • night vision problems
  • loss of BCVA
  • loss of contrast sensitivity
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14
Q

regression in PRK

A

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

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15
Q

why was LASIK introduceD?

A

to stop anterior haze (would be inside the cornea)

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16
Q

what does LASIK stand for?

A

Laser
ASisted
In-situ
Keratomileusis

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17
Q

advanatges of LASIK

A
  • 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
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18
Q

how does LASIK work?

A
  • 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
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19
Q

what is waveScan?

A

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

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20
Q

when wavescan is scanning, how does it work?

A

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

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21
Q

what is the aim of WaveScan?

A

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

22
Q

why is iris registration/recognition v important?

A

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

23
Q

what form of refractive surgery is the gold standard

A

LASIK

24
Q

when is lasik an NHS treatment?

A
  • myopia after cataract surgery
  • treating corneal graft astigmatism
  • severe disability (motoneurone disease, parkinsons, stroke patientts, friedreichs ataxia) - UNABLE TO WEAR GLASSES
25
Q

what are the 5 main refractive groups

A
  • simple myopia
  • astigmatic myopia
  • hyperopia
  • astigmatic hyperopia
  • mixed astigmatism
26
Q

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

A

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

27
Q

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

A

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

28
Q

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

A

LASEK

29
Q

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

A

SAFETY
efficacy
stability
cost
predictability

30
Q

pre-operative complications of LASIK

A

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

31
Q

operative complications of LASIK

A

poor preparations
sterility issues
equipment related
technique related

32
Q

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

A
  • 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
33
Q

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

A

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

34
Q

how does repositioning the flap avoid flap complication in LASIK?

A

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

35
Q

why does a macerated flap occur?

A

due to a faulty blade

36
Q

post-op complications of lasik

A
  • flap macro and micro striae
  • debris
  • displaced flaps
  • corneal surface problems
  • DRY EYE
  • DLK - diffuse lamellar keratits
  • infective keratitis
  • epithelial ingrowth
37
Q

why do striae occur in LASIK?

A

meibomian secretions get under the flap

38
Q

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

A

dry eye disease (30% of px’s)

39
Q

what problems does epithelial ingrowth cause?

A

optical problems
melting - keratolysis
FB sensation

40
Q

why does dry eye disease occur post LASIK?

A

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

41
Q

how do you manage dry eye disease with laser?

A

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

42
Q

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

A

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

43
Q

why would you do LASIK retreatment?

A

fine tuning

44
Q

what is DLK? diffuse lamellar keratitis

A

white granular cells in peripheral infiltrate (under the flap)

45
Q

what is corneal ectasia?

A

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

46
Q

who is more likely to get corneal ectasia?

A

high myopes (ofc) and ppl with thin corneas

47
Q

how do you prevent post-LASIK ectasia?

A

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

48
Q

which laser is used to make a corneal flap?

A

femtosecond photodisruption

49
Q

how does femtosecond photodisruption work?

A

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

50
Q

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

A

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??”

Eye Disease (48 decks)

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