Corneal Crosslinking Part A - Eye Center of Northern Colorado, P.C.
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Transcript Corneal Crosslinking Part A - Eye Center of Northern Colorado, P.C.
Northern Colorado Eye Center
Continuing Education Event
Corneal Collagen Cross-linking
September 20, 2014
S. Lance Forstot, MD, FACS
Corneal Consultants of Colorado
Founding Partner
Clinical Professor of Ophthalmology
University of Colorado Medical School
Ultraviolet Light
• UVC
– 220-290nm
– Blocked by ozone layer
• UVB
– 290-320nm
• UVA
– 320-340nm
Ultraviolet Light
• UVA
– Can induce corneal endothelial damage
with surface dose of 42.5 J/cm2
– Typical dose for CXL only 5.4 J/cm2
– Estimated dose received by cornea in
15-20 min of sun exposure on a summer
day
Real World UV
Hawaii in Spring
Australia in Summer
All Exposed Tissues:
Spring 170-200J/cm2/day in 3-4 hrs outdoors
Fall ~60J/cm2/day of solar UVA
Cornea:
5J/cm2 in 15-20 min in Summer
Safety of Cross-Linking
Endothelium
Damage threshold
3.00 mW/cm²
0μm
100%
3.00 mW/cm²
100μm
50%
1.49 mW/cm²
200μm
25%
0.74 mW/cm²
300μm
12%
0.36 mW/cm²
400μm
6%
0.18 mW/cm²
500μm
3%
0.09mW/cm²
0.06
600μm
2%
mW/cm²
How much UV – light gets into the
eye ?
70 J/cm2
0.65 J/cm2
5.4 J/cm2
Radiant exposures
0.46 J/cm2 (9 %)
0.33 J/cm2 (7 %)
0.14 J/cm2 (2.1%)
0.12 J/cm2 (1.9%)
Radiant Energy is
Below Damage
Threshold
Damage thresholds
70 J/cm2
7.7 J/cm2
Safety of UVA-Riboflavin
Cross-Linking of the Cornea
Min pach of
400 μm
protects
endothelium,
lens, retina
300 µ
Spoerl, et. al Cornea 2007; 26:385-389
Riboflavin (Vitamin B2)
• Critical role in CXL
• Increases UVA absorption to 95% in
saturated corneas (versus 32%
w/o)
Riboflavin
Diabetics, KCN and CXL
Diabetics don’t
often develop adv
KCN because of
natural cross-linking
from sugars and UV
light
Seiler T, Huhle S, Spoerl E, Manifest Diabetes
and Keratoconus, Graefe’s Arch 2000
CXL – UVA+Riboflavin
• Results in increase in biomechanical
rigidity (stiffening)
• Strongest effect in anterior 300u
– Which plays major role in
maintaining corneal curvature
• Results in corneal flattening and and
reduction in spherical equivalent
CXL with Riboflavin
Stiffened Cornea
• ↑Rigidity
• In Europe since
1998
• New Tx in US
• KCN, pellucid,
ectasia, post-RK
Normal Cornea
Scanning Electron
Microscopy
CXL
• Mechanism
– Not completely understood
– Riboflavin known to generate active
oxygen species (singlet oxygen and
superoxide anion radicals)
Confocal Microscopy
Pre op
1 m postop
3 m postop
• Apoptosis 300 μm deep after
CXL
• Repopulation takes 6 months
6 m postop
Courtesy of Dr.
Caporossi,
Crosslinks Between Collagen Fibers
Strengthens Cornea like Ladder
Rungs
Cross-Linking is Not New
• Hardening of polymers in
materials science since
1930s
(silicone oil→rubber ball)
• Dentists XL for decades
• Normal aging of connective
tissue involves cross-linking
and stiffening
• KCN progression ↓ with age
We All “Crosslink” as we Grow Up
History of CXL
• Basic research 1993-97
by Seiler & Spoerl
• First patients Txd in 1999
• Today over 400 centers
worldwide
• Standard of care for KCN
(in Europe as young as 9)
CXL Technique
•
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Anesthetic drops, painless
Prepare cornea
Riboflavin drops for 30 mins
UV light for 30 mins
Bandage contact lens
Riboflavin 0.1% Drops
Patient’s View of UV Light
UV-A Light
CXL & Curvature Change
Change in avg or steep
K does not provide key
info
See diff maps to
appreciate true
curvature changes
Preop
Postop 11 M
Difference Map
3D
Flatter
5D
Steeper
Preop
450 um
6 M Postop
411 um ( 8.6%)
Pachymetry Maps
9 M Postop
429 um
12 M Postop
450 um
56 yr old male with Keratoconus: Epi-On CXL OS
Pre Op
6 months Post
Op
UCVA
CF
100
BSCVA
25
20
Refraction
-7.75+0.75x150
-3.75 +1.50 x
180
6 months
Preop
Difference Map
William Trattler, MD case
CXL: Epi-On v. Epi-Off
Epi-On Crosslinking for Ectasia
38 year-old male with post-Lasik ectasia
OD
UCVA
Refraction
BSCVA
Pre Op
200
-3.50+6.50x180
30
3 Months
50
-0.75+1.75x175
25
Post Op 3 Months
Pre Op
Difference Map
William Trattler, MD case
BSCVA Comparison
BSCVA Comparison
Summary of Epi-ON
• EPI-On CXL
– Benefits:
• Faster visual recovery/less pain
• Reduced risk of pain/haze
• Very good clinical results
– Even in keratoconus patients over the age of 35
– Downside:
• Longer procedure (30-50 min longer)
• Can not combine with simultaneous topo-guided
PRK
William Trattler, MD
Final Points
• Epi-On can be as effective as Epi-Off
– Technique differences can explain differences in
results
• Age is not a major factor
– Older patients can benefit from crosslinking
• Progression is not required for successful results with
crosslinking
– Non-progressive patients can achieve improvement in
corneal shape, UCVA, and BSCVA
Long-term Results
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•
•
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•
241 eyes
Follow-up 6 months to 6 years
Flattening: 2.68 D at 1 year; 4.84D at 3 years
BCVA improvement (> 1 line): 53% at 1 year
No BCVA lines lost
2 patients had KCN prog and repeat CXL
Raiskup-Wolf, Hoyer, Spoerl.
J Cat Ref Surg May 2008
(Also AJO April 2010)
Long Term Results
5 year study, 48 eyes (60 pts treated)
No patient had prog of keratectasia.
Postop avg improvement 2.87 D
Improvement in BCSVA by 1.4 lines
Wollensak G. Crosslinking treatment of progressive keratoconus: New hope.
Curr Opin Ophthalmol. 2006 Aug;17:356-60
CXL for KCN, Ectasia
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•
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Shown safe and effective worldwide
Arrests KCN progression (95+%)
UCV, BCSVA, CL tolerance ↑ (60-80%)
Ideal candidates ≤ 45 y/o, corneal
thickness ≥ 400 µm, limited scarring
• Minimum age in Europe now 9 y/o
CXL Complications
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Infectious keratitis – bacterial, fungal
Sterile ulceration
Corneal haze
HSV keratitis
Corneal edema
After CXL
•
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•
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Ring segments
PRK
Topo-guided PRK
Better PKP Results?
Topographically-Guided Ablation
Developed by Theo
Seiler
Over 22,000 curvature
points on the cornea
Linked to excimer laser
Main indications irreg
astig, decentered
ablations, small OZ
Topography
Ablation
More tissue
removed
CXL
Other Applications
– Corneal edema
– Infectious Keratitis
– Radial Keratotomy
CXL and Ortho-K
CXL and the FDA
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Current status -Investigational
Physician IND
IRB Trials
FDA Trials
Thank you for your attention
S. Lance Forstot, MD, FACS
• www. corneacolorado.com
• [email protected]