collagen crosslinking, history, new techniques, kxl, pixl transepithelial crosslinking

1. CORNEAL COLLAGEN
CROSSLINKING
PRESENTER: DR PIYUSH TEWARI
MODERATOR: DR HARSHA NAGARAJ

2. Pathogenesis of Keratoconus
• Epithelial abnormality
• Fewer chains in Keratan sulphate
• Superoxide dismutase mutation on Chr 21
• Visual system homeobox 1 (VSX1) mutation
• Upregulation of MMP9, TNF-a and IL6 in tear.
Low LOX
• Eye rubbing and Bowmans microtrauma
Invest Ophthalmol Vis Sci. 1989 Oct;30(10):2278-81. Altered keratan sulfate epitopes in keratoconus
Funderburgh JL1, Panjwani N, Baum J
Oxidative Stress in the Pathogenesis of Keratoconus and Fuchs Endothelial Corneal Dystrophy; Int. J. Mol.
Sci. 2013, 14(9), 19294-19308; doi:10.3390. Wojcik AK, Kaminaska A, Blasiak J

3. Diabetes/ageing
• Diabetes has an inverse relation
• Ageing has an inverse relation
Techniques for stiffening the cornea. J Refract Surg. 1999;15:711–13. Spoerl E, Seiler T.
Association between diabetes and keratoconus: a case-control study. Cornea. 2014 Dec;33(12). Naderan
M,Pahlevani R

4. History of Corneal Cross Linking
• Theo Seiler a mathematician, physicist and an
ophthalmologist.
• Was advised by his dentist to undergo
crosslinking of tooth fillings to harden them.
• Crosslinking was used to harden heart valves,
arterial grafts and joint cartilages.

6. Theories of Crosslinking
• Activation of Riboflavin to triplet state
• Release of singlet O2
- and superoxide anions
• Ionization of amino groups (histidine,
hydroxyproline, hydroxylysine, tyrosine, and
threonine amino-acid residues)
• Formation of new bonds

9. TOXICITY THRESHOLDS

10. Dresden protocol
• Complete epithelial removal in 7 mm zone.
• Iso-osmolar Riboflavin 0.1% in T500 -20 %
Dextran. 1 drop every 3 min for 30 mins.

11. • Checking saturation of cornea by presence of
riboflavin in anterior chamber(blue light).
• Checking the calibrations irradiance.
• Intraoperative pachymetry (>400 microns)
• Ultraviolet exposure at 3mw/cm2 for 30 mins.

12. 2003 in 22 eyes
STEEP K FLATTENING BY 2D IN
70%
STABLE IN 5 EYES
PROGRESSION 0.28F IN 1 EYE 23% OF CONTROLS PROGRESSED
BCVA IMPROVEMENT BY 1.26
LINES
2008 in 111 eyes
1 YEAR 2 YEAR 3 YEAR
STEEP K  2.29D  3.27D  4.34D
BCVA STABLE STABLE STABLE IN 96%

13. Sienna Eye cross study
(Caporossi Crosslinking Technique)
• CBM illuminator - X linker VEGA
• Sharper focus
• Low power LED source
Enrolled 363 eyes with progressive keratoconus
• Definition of progression: Only states that it was defined
"clinically and instrumentally within 6 months"
● 44 eyes with ≥48 months of data post-CXL

14. PARAMETER 48 MONTH FOLLOW UP
K topographic value reduction of > 2D
UCVA Improvement of 2.7 lines
BSCVA Improvement of 1.9 lines
MRSE +1.87D at 4 years
CYLINDER NO SIGNIFICANT CHANGE
PACHYMETRY NO SIGNIFICANT CHANGE
Symmetry Improvement of > 70%
Aberrations Significant reduction in comatic aberrations
Long-term results of riboflavin ultraviolet a corneal collagen cross-linking for keratoconus in Italy: the Siena eye
cross study.
Am J Ophthalmol. 2010 Apr;149(4):585-93. Caporossi A, Mazzota C, Biaocci S

15. Many names
• Collagen Cross-linking
• C3R
• CXL
• KXL
• Holocomb C3R
• CCL

16. Indications
• Keratoconus
• Pellucid marginal degeneration
• Post lasik ectasia
• Corneal melting
• Infectious keratitis

17. Keratoconus
• Documented progression
• Pachy < 400 microns (post epithelium)
• Female
• Young patient
• Family history
• Severe allergy

18. Indications
Keratoconus
• Documented progression
• Increase in steep K by > 1-1.5D
• Corresponding change (>1-1.5D ) in refraction
5% or more in thinnest pachy in 6 months
Assessing progression of keratoconus: novel tomographic determinants. Eye and Vision20163:6. Belin M,
Borgstrom M

19. Ideal candidates
• Mild to moderate
• Pachymetry >400 microns after epi removal
• Little or no scarring
• BCVA better that 20/40
• Earlier in the disease

20. Preoperative evaluation
• UCVA/BCVA
• Refraction
• IOP
• Endothelial status
• Any signs of herpetic eye disease
• Limbal stem cell deficiency
• h/o contact lens use
• Pentacam
• h/o allergic eye disease
• h/o eye rubbing
• Previous pregnancy/ planning of pregnancy.

21. Patient education
• Not a refractive surgery
• Earlier treatment = better for the patient
• Preventing > fixing problems
• Pts. usually still need specs and/or CLs,will
need to be refit postop
• Legal obligation: 10-25 % transplantation

22. Contraindications
• Corneal thickness post epi debridement 300-
350μ
• Very young patient
• Pregnancy/nursing
• Severe corneal opacity
• Collagen vascular disease
• Prior Herpetic infection
• Poor wound healing
• Autoimmune disease
Biomed Res Int. 2014; 2014: 140461. Outcome of Corneal Collagen Crosslinking for Progressive Keratoconus in
Paediatric Patients Deepa Viswanathan, Nikhil L. Kumar,John J. Males 1

23. Procedure
• Epithelial removal
• Riboflavin types
• Soaking times
• Irradiation times
• Energy levels

24. Epithelium Removal Techniques
Manual Scraper
Epiclear blade
Alcohol removal
PTK
Dayas disruptor

25. Riboflavin Solutions
• MEDIOCROSS –D
• 0.1% Riboflavin + T500 D20 DEXTRAN
• Isotonic

26. Riboflavin Solutions
Ribocross TE
• Epi Off
• Epi On
• Post keratitis
• Post lasik ectasia

27. Riboflavin Solutions
• Vibex XTRA
• 0.22% Riboflavin, Saline, Isotonic
• Procedure
• Lasik Xtra
• Application
• Stromal Bed

28. Riboflavin Solutions
• VibeX Rapid
• 0.1% Riboflavin, Saline, HPMC

29. Riboflavin Solutions
Photrexa Viscous
• 0.146% Riboflavin 5 phosphate in 20 Dextran
• For use with KXL system
• FDA approved for progressive keratoconus.

30. Protocols
RIBOFLAVIN EPITHE
LIUM
IMPREGNATION UV
FLUENCE
TIME ENERGY
0.1% + 20% DEXTRAN
(CONVENTIONAL)
MEDIOCROSS -D
OFF EVERY 2 MIN FOR
30 MIN THEN
EVERY 5 MIN
DURING FLUENCE
3mW/cm2 30min 5.4J/cm2
0.1% + 1.1%
METHYLCLLULOSE
(CONVENTIONAL)
MEDIOCROSS -M
OFF EVERY 2 MIN FOR
30 MIN THEN
EVERY 5 MIN
DURING FLUENCE
3mW/cm2 30min 5.4J/cm2
0.1% + 20% DEXTRAN
(ACXL)
OFF EVERY 2 MIN FOR
20 MINS
30mW/cm2 3 min 5.4 J/cm2
0.1% + 20% DEXTRAN
(ACXL)
OFF EVERY 2 MIN FOR
20 MINS THEN
EVERY 2 MIN
DURING FLUENCE
18mW/cm2 5 min 5.4J/cm2
0.25% + HPMC, NaCl ,
EDTA, Benzalkonium
(TECXL) MEDICROSS TE
RIBOCROSS TE
ON EVERY 2 MIN FOR
30 MIN
45mW/cm2 2min 40 sec 7.2J/cm2
0.5% with 0.9%NaCl
(Hyposmolar for pachy
<400 microns)
OFF EVERY 3 MINS FOR
30 MINS THEN
EVERY 20 SEC FOR
5 MINS
3MW/cm2 30 mins 5.4J/cm2

31. Many Variations
• Accelerated Crosslinking
• Hypo-osmolar cross-linking
• Transepithelial cross-linking
• Contact lens assisted
• Intrastromal cross-linking

32. Acclerated Crosslinking
• Principle: Bunsen Roscoe law of reciprocity:
-a certain biological effect is directly
proportional to the total energy dose
irrespective of the administered regime
Constant radiant exposure of 5.4 J/cm2

33. Acclerated Crosslinking
• Riboflavin drops every 30 sec for 10 mins
• 30 mw/cm2 for 3 mins

34. Acclerated Crosslinking in young
• Purpose. To evaluate the effectiveness and safety
of ACXL in patients below 14 years of age with
progressive keratoconus.
• Materials and Methods. 38 eyes with progressive
keratoconus underwent preoperative and
postoperative visual acuity assessment,
topography, and specular microscopy prior to
ACXL and were followed up for 24 months
• Results. Improvement in the mean postoperative
UCVA, BCVA, mean spherical refraction , mean
cylinder.
• Shetty R, Nagaraj H, Jayadev C, Kurian M, Pahuja N. Accelerated Corneal Collagen Cross-Linking in Pediatric Patients:
Two-Year Follow-Up Results. Biomed Res Int. 2014; 2014: 894095.

35. Hypo-osmolar crosslinking
• Indications: thinnest pachy < 400 microns post
epithelium removal
• Method:
Riboflavin 0.1% iso-osmolar in 20 %
dextran every 3 mins for 30 min.
Ultrasound pachy at thinnest point
Riboflavin 0.5% with 0.9% NaCl every 20sec
for 5 mins/ pachy > 400 microns
Hafezi F, Mrochen M, Iseli HP, Seiler T. Collagen crosslinking with ultraviolet-A and hypoosmolar riboflavin solution in
thin corneas. J Cataract Refract Surg. 2009 Apr;35(4):621-4. doi: 10.1016/j.jcrs.2008.10.060..

36. • Raiskup and Spoerl published results of 32
eyes undergoing Hypo-osmolar KXL.
• Hypoosmolar riboflavin 0.1% solution every 2
min for 30 min. Every 2 mins during
irradiation.
• Reported stabilization in terms of mean K
value and BCVA
Raiskup F, Spoerl E. Corneal cross-linking with hypo-osmolar riboflavin solution in thin keratoconic corneas.
Am J Ophthalmol. 2011;152:28–32

37. Transepithelial Crosslinking
• Proparacaine eye drop every 5 min for 15 min
• Enhanced penetration by EDTA
• Riboflavin application by pre-soaked sponge or
pooling the cornea in a silicon well

38. EPITHELIUM ON EPITHELIUM OFF
Described by Boxer Wachler in 2004 and then by Pinelli. Described by Seiler, Wollensack and Spoerl
It uses modified Riboflavin. 0.1% in 15% Dextran T500 with
EDTA and Trometamol
Standard Riboflavin
Uses Off Label medical UV light source UV light from FDA Approved IROC group (Avedro)
Cannot be combined with Topoguided procedures. Can be combined with TPRK
Less haze and faster recovery More incidence of haze and relatively slower recovery.
Can use in corneas <400 microns Not recommended for <400 microns corneas.
Incidence of progression is higher. Incidence of progression is lower.

39. Contact Lens Assisted CXL - CACXL
Indications: Stromal thickness of 350- 400 m after epi
removal.
Mechanism: Precorneal riboflavin layer, contact lens
and pre CL riboflavin layer help in endothelial
preotection.
Method : Lidocaine 2% and Pilocarpine 2% are used
easy endothelial removal and ocular protction.
Contact lens is soaked in 0.1% riboflavin solution for
30 mins prior, then placed over de-epithelialized
stroma.
J Refract Surg. 2014 Jun;30(6):366-72. doi: 10.3928/1081597X-20140523-01. Contact lens-assisted collagen cross-linking (CACXL): A
new technique for cross-linking thin corneas. Jacob S, Kumar DA Agarwal A, Basu S, Sinha P, Agarwal A.

40. Contact Lens Assisted CXL
CACXL

41. Intralase Crosslinking
• In early disease Corneal pocket of 100 micron
depth is created.
• 0.1 % Riboflavin for 2 minutes
• 7 mW/cm2 for 15 mins
• crosslinks 60 microns anterior and 200
microns posterior.

43. Post Lasik Ectasia
Sanchez Leon technique
• Flap edge is identified
• 10 deg edge is lifted using Sinkey hook
• Intralase spatula is used to make a pocket
similar to SMILE procedure.
• 0.1 % Riboflavin into stroma 2 times at 15
mins interval
• 3mw/cm2 for 30 mins

44. Crosslinking in Nonresponding ulcers
• Standard crosslinking in corneal ulcers not
responding to maximal topical medications.
• Disinfection of microbes by UV light.
• Tissue stabilization.

45. SWISS PACK CXL
• Principle: UV-A with riboflavin reduces
pathogen load in platelets in transfusion
medicine.
• Design: Interventional, randomized,
longitudinal, multicentric
• Started: March 2016
• Expected primary completion: March 2018
• Principal investigator: F Hafezi (Univ Hospital)
Geneva

46. • Primary outcome measures: Time to re-
epithelialization
• Secondary outcome measure: time from
treatment to discharge of patient
* Arms:
Experimental Comparator
Tetracaine drops every 3 mins for 3 times Cephazolin (5%)
Flouroquinolone
CyclopentolateCorneal scraping 1 mm around infiltrate/ulcer.
Hypo-osmolar riboflavin every 2 min for 20 min.
3 mW/cm2 for 30 min

47. CROSS LINKING FOR CORNEAL
ULCER TREATMENT TRIAL (CLAIR)
Interventional
Phase 4
recruitment of about 266 patients
12 months follow up
Aravind Eye Hosp, Madurai
Supported by University of California

48. Arms of the study
For Fungal keratitis
1.collagen cross-linking + amphotericin;
2.collagen cross-linking + natamycin;
3.amphotericin alone;
4.natamycin alone
For Bacterial keratitis: Cephazolin +
Gentamicin/amika

49. TPRK + KXL
Purpose: To regularize the corneal surface and
make the patient more tolerant to contact lens.
Ideal Candidate:
• CL intolerant
• Pachy > 450 after epithelial debridement
• Early stage

50. TPRK + KXL
Purpose: To regularize the corneal surface and
make the patient more tolerant to contact lens.
Ideal Candidate:
• CL intolerant
• Pachy > 450 after epithelial debridement
• Early stage

51. 5
1
Photorefractive intra
stromal corneal
collagen cross- linking
(PiXL)

52. • RUB university - Germany
• Using KXL II system (Avedro Inc.)
• For moderate myopic refractive correction
• Inclusion criteria-
• Age >18 years;
• BCVA >/= 0.6 logMAR
• Myopia: Group I- MRSE -1.0 D to -1.75 D, cyl.
Max. -0.75 D
Group II- MRSE -2.0 D to -3.0 D, cyl. Max.
-0.75 D

53. • Prospective study
• Duration: 12 months
• 40 eyes in 2 groups
• Phakic & pseudophakic eyes.

54. 5
4
•4mm circular spot
•Centered on corneal vertex
•0.1% Riboflavin with HPMC soak for 10 mins
•UVA 365nm wavelength light source with
programmable illumination pattern
•30mW/cm2 irradiation (1:1 pulse), max dose
15J/cm2

55. 5
5
• Significant improvement of UCVA at 3 months.
• BCVA – stable
• Refractive change (at 6 months)
- 15J group – 1.375D, 25 letter improvement
- 10J group – 1.0 D, 17 letter improvement

56. 5
6
• Eagle eye institute - MA, USA
• 12 patients (5 males, 7 females)
• Mean age —> 31.1(0.63) (23-51 years)
• 18 myopic eye —> mean- 1.5 D(0.63) (range: - 0.5 to -
2.63D)
2

57. •Treatment zone - 4.5mm
•Pulsed illumination 1sec on, 2 sec off
5
7
• Riboflavin 0.25% - 10 minutes soak
• UVA irradiance 365nm - 45mW/cm2
2
11 min 11
sec16 min 39
sec

58. 5
8
• Mean MRSE reduction - 0.72D (0.43D)
• Mean gain in unaided VA: 0.25 log unit
• 69% achieved 6/9 or better
• Average K mean flattening 0.36 D (0.23 D)

59. 5
9
• Refractive procedure for low- moderate myopia (≦ -2.0
D in healthy eyes)
• No tissue ablation
• Safe and stable at 12 months follow-up
• Long term stability unknown

60. In Our Setup
• Riboflavin -0.1 % - 10 min
• Treatment zone - 4.5mm
• UVA radiation - 30mW/cm2 irradiation (1:1 pulse),
max dose 15J/cm2
• Supplemental oxygen

61. Post Op
• Epithelial defect heals in 3-5 days
• Mild steroid drops for 4 weeks
• Topography at 3 months
• can use old RGP lens after 2 weeks

62. COMPLICATIONS
• Temporary stromal edema (up to 70%),
temporary haze (up to 100%), and permanent
haze (up to 10%)
• Corneal scarring and sterile infiltrates
• Infectious keratitis:
Bacterial/protozoan/herpetic
• Diffuse lamellar keratitis (DLK) in a post-LASIK
patient
Mazzotta C, Balestrazzi A, Baiocchi S, et al. Stromal haze after combined riboflavineUVA corneal collagen cross-linking in
keratoconus: in vivo confocal microscopic evaluation. Clin Experiment Ophthalmol 2007;35:580e2
Pollhammer M, Cursiefen C. Bacterial keratitis early after corneal crosslinking with riboflavin and ultraviolet-A. J Cataract
Refract Surg 2009;35:588e9.

63. 63
Thank You