2. Introduction
• Refractive fellowship course Zurich,
Switzerland
• Prof Michael Mrochen and Prof Seiler at
the IROC eye center in Zurich, Switzerland
15. Examination
• Degree of correction
– Myopia –12
– Hypermetropia +5
– Astigmatism
• Corneal keratometry
– Average K > 48.5 or < 40
• Corneal vascularization
16. Examination
• Corneal thickness
– Usually >500um, Leave > 250um
• Ablation depth
– Ablation depth approx 20um per diopter
– Example: Pt with refraction of –6D
corneal thickness = 520um
flap = 160um
6 D ablation = 120um
residual bed = 520 – (160 +120)
= 240 um
17. Examination
• Pupil size
– In the dark
– Caution >8mm
• Surgical exposure
– Small deep palpebral fissure
• Dry eye
– Consider pre and post operative treatment
18. Risks / Complications
- Over-correction & under-corrections. Less15%
and it depends on the initial refraction.
- The higher the refractive error is the greater the
chance of having under-correction.
- Enhancements may be done three months or later
if the cornea is thick enough (10%)
- Infection.
-Corneal flap complications.
19. Risks / Complications
- DLK deep lamellar keratitis or Sands of
Sahara
- Epithelial ingrowth
- Night glare. This is normally present for
the first few months. Depends on the optical
zone and pupil size.
- Haze.
- Corneal ectasia
21. Corneal topography
• To detect irregular astigmatim
• Keratoconus and subclinical (formfrust)
• Pellucid marginal degeneration
• Detect stability of corneal warpage from
contact lenses
• Stability of cornea post lasik
22.
23. Corneal topography
• Method of capture very NB
• Irregular surface from dry eyes
• Extrapolation of data
• Provides laser ablation profiles for
topography guided treatments
27. Aberometry
• Wavefront analysis
• Measures the overall performance of the
eye
• Measures aberations of the eye
• Provides laser treatment profiles for
wavefront guided treatments
• Needs to be very accurate
34. Laser treatments
• Wavefront optimized
– Maintain the physiological condition
– Reduce the number of aberations that are
created by the laser
– especially spherical aberations
35. Laser treatments
• Q-value adjusted ablations
– Hyperprolate cornea for enhanced monovision
– Increase depth of focus by increased
prolateness of the cornea (add +1D)
– In addition myopia in the non-dominant eye (-
0.75D to –1.5D)
– Dominant eye plano
40. Laser treatments
• Topography guided
– Therapeutic treatments for vision enhancements
– Unable to measure total aberrations of the eye,
or not reproducible
– Corneal based problems
• Scars
• Retreatments
45. Microkeratomes
• Use a blade to cut corneal flap
• Suction ring
• Microkeratome
• Manual and automated
• Some variability in flap thickness
46. Femtosecond lasers
• Significant advance in the field of refractive
surgery
• Focusable infrared laser similar to the Nd-YAG
used for posterior capsulotomy
• Ultra fast firing in the femtosecond range (100
times 10 power of 15)
• Causes photodisruption…..tissue vaporization…
gas bubble formation in the stroma
• Thermal damage to adjacent tissue only 1um
47. Femtosecond lasers
• Software is able to create different flap
shapes and edges
• Control flap size, thickness, hinge location
• More predictable
• Less complications
50. Case 1
• 40 year old women
• Rigid gas permeable CL for 15 yrs (now
intolerant)
• Graves/thyroid eye disease
51. Case 1
• Wearing
– OD -3.25/-1 @ 168 VA 20/20
– OS -2/-0.5 @ 35 VA20/20
• Manifest
– OD –3.5/-1.25 @ 160 VA20/20
– OS –2.5/-0.75 @ 45 VA20/20
• Cycloplegic
– OD –3.5/-1.5 @165
– OS –2.5/-0.5 @ 35
• Keratometry
– OD 41 @170 and 43 @80
– OS 42.12 @35 and 43.75 @ 125
52. Case 1
• Pachmetry
– OD 548 um
– OS 552 um
• Topography
– Regular astigmatism OU consistent with refraction
– Increased aberrations (spherical and coma)
• Scotpic pupils
– OD 6.9mm
– OS 6.8mm
54. Case 1
• Hard contact lenses
• Dry eyes
• Diffuse lamellar keratitis
• Wavefront guided treatment
55. Case 2
• 32 year old
• Soft contacts for 10 years
• No problems
56. Case 2• Wearing
– OD -4/-0.5 @180 VA 20/25+
– OS –4/-0.75 @ 180 VA20/30
• Manifest
– OD –4.25/-0.5 @180 VA 20/20
– OS –4.5/-0.75@175 VA 20/20
• Cycloplegic
– OD –4.25/-0.5 @180
– OS –4.5/-0.75 @180
• Keratometry
– OD 43 @180 / 43.5 @90
– OS 42.5@ 180 / 43.5 @90
57. Case 2
• Pachymetry
– OD 475um
– OS 480um
• Topography
– Regular bow tie
• Scotopic pupil
– OD 6.5mm
– OS 6.5mm
58. Case 2
• Examination
– Normal
– Thin corneas ? PRK
– Orbscan shows posterior elevation of 47um in
the R and 49um in the L.
– What are the risk factors for keratoconus and
formfrust keratoconus?
59. Case 2
• Risk factors for keratoconus
– Changing prescription
– Inferior steepening and superior flattening
– Posterior elevation of cornea
– High K’s (>47.2)
– High astigmatism
– Asymetry between superior and inferior corneal power
– Corneal thickness
60. Case 3
• 45 year old business executive
• Never worn glasses
• Good VA till 2 years ago when he started
using reading gls
• Now uses them for driving as well
• Otherwise in good health
61. Case 3
• Wearing
– +2 readers VA 20/60 OU
• Manifest
– OD +2 VA 20/40
– OS +2 VA 20/40
• Cycloplegic
– OD +4.75 VA 20/20
– OS +4.5 VA 20/20
• Keratometry
– OD 45.5 @ 180 /45.75 @90
– OS 45.5 @180 /45.5 @90
62. Case 3
• Pachymetry
– OD 555 um
– OS 547 um
• Topography
– Mild inferior steepening, post elevations
normal
• Scotopic pupil
– OD 5.2 mm
– OS 5.2 mm
64. Case 3
• Discussion
– Uncorrected hyperopia
– Most of these pts believe they have excellent
vision despite poor VA
– They try to go without gls for as long as they
can
– Often unhappy after correction unless you
correct prebyopia as well
65. Case 3
• So what procedure?
– Cycloplegic refraction falls within range of
hyperopic Lasik, but:
• decreased accuracy and unable to do monovision
• Keratometry too steep after treatment
• Corneal diameter too small. Hyperopic lasik
requires large flap and treatment zone.
• PRK may avoid these problems
66. Case 3
• Advised against Lasik
• Full gls correction was not tolerated
• Progressive increase with contact lenses was
tolerated better and reading gls over
• In the end he gave up on this because he said his
vision was worse after removing the contacts
• Clear lens extractions were recommended with
restore multifocal IOLs
Notas do Editor
No microkeratome Thinner corneas
Reading, night driving Risk free surgry does not exisit Quality of va is not just va …….glare, gosting, contrast, decreased near Need for re treatment
ker
Large pupil….custom ablation Femtosecond Plugs, tear suplements, cyclosporin
Infection less than conatct lens
To detect
Until recently unable to meausre higher order aberations
undercorrected
Needs to be out of hard contacts for long enough to ensure corneal stab if in doubt or diff between refract and topo wait Dry eye pretreat Treat bleph with doxy and scrubs, increased DLK Wave front appropriate because consistency and higher aberations
B/w 40 and 50 suspicios for keratokonus > 50 is keratokonus
