Intraoperative and Long-Term Corneal Biomechanical Changes

in Crosslinked Keratoconic Eyes

Elena Albé MD Elena Albé MD

Paolo Vinciguerra MD, Paolo Vinciguerra MD,

Silvia Trazza, MD Silvia Trazza, MD

EYE OCULISTICA Istituto Clinico Humanitas

Rozzano, MI, ItalyDirettore: Paolo Vinciguerra, MD

Boston, ASCRS, April, 2010

Financial discosure: I do not have any financial interest or relationship to disclose.

P253

AIM of the STUDYTo analyze the biomechanical properties of 24 keratoconic corneas

Amsler grade II undergoing CXL and correlate the intraoperative biomechanical and geometrical change

t 1 baseline preCXL witht 2 after epithelium removal preCXL sinet 3 after impregnation before UVA preCXL sine2t 4 after CKL procedure postCXL sinet 5 after reepithelialization postCXL with

1,6,12 and 24 months after CXL by means of CSO TOPOGRAPHER OCULAR RESPONSE ANALYZER PENTACAM

CROSS LINKING PROCEDURE•2% Pilocarpine drops and antipain meds 30 min before CXL.•Oxybuprocaine hydrochloride 0.2% 5 min before CXL.•LASER TEST UVA meter

•Laser 370±5 nm•Power 3 mW/cm2 (= 5.4 j/cm2)

•RICROLIN riboflavin 0.1% solution instillation each minute for 30 min•Riboflavin check absorption in anterior chamber (flare).•UVA Light Corneal irradiation PESCKE X-Linker 7.5 mm Ø. •RICROLIN instillation 6 times of 5 min each•Bandage soft CL application and levofloxacin eyedrops

RESULTSCH and CRF

9,13

8,34

10,08

9,06

14,51

13,12

15,09

14,02

10,04

10,93

0

2

4

6

8

10

12

14

16

PRECXLwith BeforeUV afterRE-EPI

CH

CRF

p<0.05p>0.05 p<0.05 p<0.05

preCXL with

preCXL sine

AfterCXL

BeforeCXL

AfterRE-EPI

RESULTS RESULTS CHCH Corneal HysteresisCorneal Hysteresis

9,6810,32

15,18

12,48

9,57 9,61

0

2

4

6

8

10

12

14

16

CH

Statistical significance Statistical significance pp<0.05<0.05

p>0.05 p<0.05 p<0.05

PRE XLWITH EPI

PRE XLWout EPI

POST XLWout EPI

1 monthPOST XL

1 yearPOST XL

p>0.05

2 yearsPOST XL

p>0.05

CRFCRF Corneal Resistance Corneal Resistance FactorFactor

9,05 9,42

14,15

12,53

9,01 9,1

0

2

4

6

8

10

12

14

16

CRF

Statistical significance Statistical significance pp<0.05<0.05

p<0.05p<0.05p>0.05

PRE XLWITH EPI

PRE XLWout EPI

POST XLWout EPI

1 monthPOST XL

1 yearPOST XL

p>0.05

2 yearsPOST XL

p>0.05

RESULTSPeaks

247

187

229

153

202

139

172

131

0

50

100

150

200

250

PRECXLwith

postCXLsine

Peak 1

Peak 2

p<0.05p<0.05

preCXL with

preCXL sine

AfterCXL

AfterRE-EPI

p<0.05

Peak 1 and Peak 2

276228

493444 439

346

452

384

050

100150200250300350400450500

PRE XL 12mPOSTXL

Peak 1

Peak 2

p<0.05

p<0.05

6 monthsPOST XL

1 yearPOST XL

2 yearsPOST XL

p<0.05

p<0.05

RESULTS CORNEAL THICKNESS

462430 407 379

624

422 431 441 452

0

100

200

300

400

500

600

700

PRECXLwith afterRE-EPI 24 months ThinnestCorneaPoint

p>0.05 p<0.05p>0.05 p<0.05

p>0.05

p>0.05

p>0.05

preCXL with

preCXL sine

AfterCXL

BeforeCXL

AfterRE-EPI

1m 6m 12m 24m

p>0.05

RESULTS RESULTS IOPgIOPg

13,03 12,44

14,41

18,1

12,07 12,54

0

2

4

6

8

10

12

14

16

18

20

IOPg

Statistical significance Statistical significance pp<0.05<0.05

PRE XLWITH EPI

PRE XLWout EPI

POST XLWout EPI

1 monthPOST XL

p>0.05 p<0.05p>0.05 p>0.05

1 year POST XL

2 yearsPOST XL

p>0.05

RESULTS RESULTS IOPccIOPccStatistical significance Statistical significance pp<0.05<0.05

14,6413,45

9,92

16,71

14,25 14,32

0

2

4

6

8

10

12

14

16

18

IOPcc

PRE XLWITH EPI

PRE XLWout EPI

POST XLWout EPI

1 monthPOST XL

p>0.05 p<0.05 p<0.05 p>0.05

1 yearPOST XL

2 yearsPOST XL

p>0.05

CONCLUSIONWhat Happens during Cross Linking?

Epithelium removalIncreases corneal curvature Reduces corneal thickness Reduces light detected during applanation peaks Does not influence corneal biomechanical

properties CH and CRF

MullerLJ, Pels E, Vrensen GFJM. The specific architecture of the anterior stroma accounts for the maintenance of corneal curvature. BJO.2001;85:437-43 The specific architecture of the most anterior part of the corneal stroma (100-120 microns) has been suggested to be responsible for the stability of the corneal shape.Gatinel D, Chaabouni S, Adam PA, Munck J, Puech M, Hoang-Xuan T. Corneal hysteresis, resistance factor, topography, and pachymetry after corneal lamellar flap. JRS.2007;23:76-84The creation of a stromal flap can modify the biomechanical properties of the cornea, including a reduction of corneal hysteresis

CONCLUSIONWhat Happens after Cross Linking?

• T-dextran and riboflain dehydrate cornea along CXL

• Cornea dehydration affects biomechanical properties

• increases CH and CRF

• reduces light detected during applanation Peaks

• Rehydration and corneal oedema affect corneal biomechanical properties

• Reduces CH and CRF

• Reduces light detected during applanation Peaks

•Peak 1 and Peak 2 increase after CXL, suggesting a reduction in KC deformation.

•IOPg and IOPcc remain higher till steroid admin.

•At 24 months, CXL does not induce any change in IOP.

•CXL induces a significant reduction in corneal thickness and total corneal volume, however corneal thickness recovers at 1 year follow-up.