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P R K in 2005

Bernard Mathys, MDBrussels

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Brief history

• 15 Y of follow-up

• Excimer laser

• Relatively easy technique

• Short learning curve

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Limits

• Pain• Regression• Haze ( > -6D)

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PRK fights back

• Complications of Lasik– Epithelial ingrowth

– Striae, folds

– SOS

– Ectasia

– Flap induced HOA

– Problem flap size/wide OZ for hyperopia

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PRK improved

• Improved lasers: scanning, flying spot, Gaussian

• Improved OZ, transition Z, blend Z

• Improved nomogram

• Improved tracker: centration, cyclotorsion, frequency, mechanical response ?

• Aspheric profile: better for HOA ?

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Advantages

• Limits induced HOA

• Lower rate of irregular astigmatism

• Wave-front guided: Fourier > Zernicke ?

• Customized treatment

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Results

4,6

0,051

2,08

0,251,4

108,9

10,51

0

2

4

6

8

10

12

D/VA

refraction Std UCVA BCVA

Z-preopZ-postopS-preopS-postop

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• No higher RMS postop for high correction

• No higher RMS postop for large OZ

• Seems to reduce RMS for OZ 6 – 6.5

• Safe and effective: no loss of VA

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RMS changes

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And so…PRK, Lasek > Lasik ?

• Flap induced HOA: nomogram correction

• FDA studies for Lasik. PRK ?

• In fact, photoablation creates HOA !!

• No « real » studies in litterature

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PRK Follow-up

• Pain

• Fluctuations

• Haze

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PRK best treatment

• Corneal cooling

• Quick removal of the epithelium

• CL

• AINS (ketorolac) 3d

• Tears

• Steroïds ?

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AINS (ketorolac)

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PRK haze ?

• Activated keratocytes – collagen I-III• More frequent if:

• delayed epithelial response• deep ablation, > -9D• broad beam, more energy, retreatment Gabbato,Ophtal. online, dec

2004

• Max 3 to 6 M• Decreases with time: metalloprotease Kato • After 1 Y: scar• MMC 0.02% 2 min

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Best healing response ?

• Amniotic membrane ?

• Interferon ?

• Growth factor ?

• PA ?

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So…PRK indications ?

• Up to -5 D

• K < 39 and > 48

• KT subclinical

• Thin cornea

• Dry eyes

• High astigmatism

• Army, pilots, athlete

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Even more indications…

• Hyperopes• Refraction error after IOL• Refraction error after RK• Refraction error after corneal graft

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PRK after RK

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And PTK ?

• Irregular astigmatism

• Recurrent erosion

• Reshaping

• Herpes (under treatment)

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Then:

• Do not be ashamed to perform PRK

• Many indications

• Haze problems tend to diminish

• Lasek = disguised PRK

• Not a single ectasia after PRK

• Good PRK much better than a bad Lasik !!

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Good PRK >< Bad Lasik

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Thin corneas

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Follow-up 1 Y

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Limited induced aberrations

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High astigmatism

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Same patient, topography

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Thank you for your attention