(Mazzotta et al, 2007) Human corneal rigidity increases 329 % (Wollensak, 2006)

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Gertrude Muriel Thomas
8 years ago
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1 %, to release oxygen radicals which create new cross-linking bonds between

1 Simultaneous PRK and CXL Corneal Crosslinking (CXL): UV-A light, 365 nm, causes riboflavin, 0.1 %, to release oxygen radicals which create new cross-linking bonds between collagen lameller fibres and within collagen molecules leading to increase in corneal rigidity like what happens in aging and diabetes (Spoerl and Seiler, 1999) 1

$(Mazzotta et al, 2007) Human corneal rigidity increases 329 % (Wollensak, 2006) CXL only method that treats the original disease in keratoconus (kc), rather than just treating refractive errors.$

2 In addition to collagenaze inhibition and forming cross-links within and between collagen fibres, long-term stabilizing effect by synthesis of new collagen having different structure and resistance (Mazzotta et al, 2007) Human corneal rigidity increases 329 % (Wollensak, 2006) CXL only method that treats the original disease in keratoconus (kc), rather than just treating refractive errors. CXL effective in halting iatrogenic ectasia after corneal ablation procedures ( Seiler, 2006) 2

3 Post LASIK ectasia, although catastrophic, is considered rare. Ranges 0.04% - 0.6% It occurs from one week to several years after LASIK (Pallikaris et al,2001 and Rod et al, 2004) Kc occurs in 1:2000 in general pop. Starts in puberty, progressing in 20 % needing KP. Other TTT modalities: CL, intracorneal rings (ICR), DALK (Waller et al,2006) 3

4 No endothelial cell apoptosis and no effect on corneal clarity ( Wollensak et al, 2004) Causes corneal depopulation 300 microns deep, regeneration within 4 ms Hypo-osmolar riboflavin for thin cornea < 400 Inhibits limbal epithelial cell regeneration, so limbus should be avoided during CXL. ( Thorsrud et, 2012 ) CXL can be elective TTT for progressive kc in less than 18 years, due to higher risk of progression (Caporossi et al, 2010) CXL improved vision and diminished K readings and HOAs esp. coma (Caporossi et al, 2012 and Greenstein et al, 2012) 4

5 Signs of KC progression: (2 of ) Dim. VA > one line on Snellen chart Incr. sph./cyl. error > 0.5 D Inc. Av. K > 0.5 D Dim. corneal thick. > 10 microns (Caporossi, 2010) Expanding indications of CXL: Forme fruste KC (Hafezi, 2007) KC (Kymionis et al, 2007) PMD (Jankov et al, 2008) Iatrogenic keratectasia (Vinciguerra et al, 2009) Corneal melting (Krueger, 2008) Bullous keratopathy (Wollensak et al, 2009) Infective keratitis (Schrier et al,2009) Combined therapy: ICR, PRK, LASIK. (Wollensak et al,2012 and Kymionis et,2009) 5

6 CXL technique: Complete epithelial removal. Riboflavin 0.1% dropped every 2 mins. for 30 mins. UV irradiation at central 8 mm for 30 mins Irradiance of 3.0 mw/cm2 Riboflavin drops every 2 mins. Saline irrigation, antibiotic drops Bandage CL (Wollensak,2006,Seiler,2006 and Kremer et al 2012) Modified CXL: Transepithelial CXL: Riboflavin is hydrophylic, cannot cross intact epithelium. Two enhancers are added to help modified riboflavin penetrate epithelium (Ricolin ET) Applied in young and uncooperative patient, thin corneas and avoiding debridement Rapid PO rehabilitation, no pain ( Greenstein et al, 2012) 6

7 Accelerated CXL: Reduced exposure time while maintaining same dose UV applied for 3 mins. at a power of 30, up to 45 mw/cm2 ( Celik et al, 2012) CXL combined procedures: Combined LASIK and accelerated CXL: Promising modality to prevent corneal ectasia needs larger study. (Celik et al,2012) Risk of post-lasik ectasia: 1. Abnormal topography 2. Thin residual stromal bed (RSB) 3. Young age 4. Thin cornea 5. High myopia 6. Elevated post. float (Perez-Straziota and Randleman, 2008) 7

8 Sequential CXL and PRK: CXL and 6 ms later PRK in forme fruste keratoconus (Hafezi et al, 2007) Combined PRK and CXL in Kc and post LASIK ectasia (Athens protocol), caused less corneal haze and patient discomfort than sequential pattern (Kanellopoulos, 2010) Simultaneous PRK and CXL: Combined ttt improved visual, refractive and topographic data and stopped keratectasia progression. (Kremer et al, 2012 and Tuwairgi and Sinjab,2012) Topography-guided laser ablation treats only corneal aberrations, more specific, than wavefront-guided which treats whole eye aberrations including cornea (Kymionis et al, 2011) 8

9 Small group study of simultaneous PRK and CXL: Case 1: Female, 22 years old OD: Cyl.- 2.5/ OS: Cyl. 2.0/165 BCVA 6/6 P bilateral 9

10 PRK CXL done BUCVA : OD: 6l9 --- OS: 6/6 P 10

11 Case 2: Female, 18 years old OD: -2.0 sph., / 180 cyl. BCVA: 6/6P OS: sph., / 180 cyl. BCVA: 6/6 P 11

12 PRK CXL done BUCVA : 6/6 P bilateral 12

13 Case 3: Male patient, 29 years OD: Cyl. -3.0/15 BCVA: 6/9 OS: Cyl. -3.0/165 BCVA: 6/9 13

14 PRK-Mitomycin-CXL Scraping done:

15 Conclusion: CXL is safe and effective procedure with expanding indications and minimum complications. Combined procedures avoid and halt ectasia progression. Combinations also have synergistic effect for reverting irregular astigmatism and diminishing corneal haze and patient discomfort. THANK YOU 15

Keratoconus. Progressive bilateral ectasia. Onset puberty. Prevalence 1:2000. 20% progress to transplantation. Pathogenesis unclear

Keratoconus. Progressive bilateral ectasia. Onset puberty. Prevalence 1:2000. 20% progress to transplantation. Pathogenesis unclear Keratoconus Progressive bilateral ectasia Onset puberty Prevalence 1:2000 20% progress to transplantation Pathogenesis unclear Increased pepsin and catalase Decreased collagen crosslinking cf normal Conventional