Detection of Central Cornea Power after Myopic LASIK

1
Detection of Central Cornea Power after Myopic
LASIK

• Adriana Forseto, MD Telma Pereira, MD Lucila F.
  Pinto, MD Walton Nosé, MD

Eye Clinic Day Hospital São Paulo - Brazil
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• The authors do not have any commercial or
  proprietary interest in the subject matter of
  this paper

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Purpose

• To measure the central cornea power after myopic
  laser in situ keratomileusis (LASIK) and to
  compare the results to the refraction-derived
  keratometry (RDk) obtained with the clinical
  history method

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Methods

• Thirty-six post-LASIK eyes with a minimum
  follow-up of six months and stable postoperative
  refraction were included in this study
• To be eligible all of them should have complete
  preoperative data available

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Methods

• Postoperative evaluation included
• Manifest refraction
• Slitlamp examination
• Tonometry
• Corneal topographies

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Methods

• The last postop spherical equivalent (Sph Eq) at
  the corneal plane was subtracted from the preop
  Sph Eq at the corneal plane to obtain the
  refractive change
• The refractive change at the corneal plane was
  subtracted from the preoperative EyeSys central
  cornea power (axial map) in order to obtain the
  refraction-derived keratometry (RDk)

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Methods

• The postoperative central cornea power was
  analyzed with 2 EyeSys maps
• Axial Central (central EyeSys)
• Holladay Diagnostic Summary
• Effective Refractive Power (Eff RP)

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Methods

• The postoperative central cornea power was
  analyzed with 3 Orbscan maps at different areas -
  maparea
• Axial Central (OrbCen)
• Total Mean 2-mm (OrbMean2)(1)
• Total Optical Power 4-mm (OrbMean4 )(1)

(1)Sônego-Krone S, Lopez-Moreno G, Beaujon-Balbi
OV, Arce CG, Schor P, Campos M. A direct method
to measure the power of the central cornea after
myopic laser in situ keratomileusis. Arch
Ophthalmol 2004122159-166.
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Methods

• The postoperative central cornea power was
  analyzed with 3 Pentacam maps
• Sagital curvature (PenSa)
• Tangential curvature (PenTan)
• True net power (PenTrue)

Post Myopic LASIK Pentacam maps from the same eye
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Methods

• The calculated RDk was compared to the
• EyeSys
• Axial (central EyeSys)
• Effective Refractive Power (Eff RP)
• Orbscan
• Axial (OrbCen)
• 2-mm total mean power (OrbMean2)
• 4-mm total optical power (OrbOpt4)
• Pentacam (at the central area)
• Sagital (PenSa)
• Tangential (PenTan)
• True net power (PenTrue)

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Results

• Preoperative data
• Spherical equivalent
• -3.53D1.43D (range, -6.50D to -1.13D)
• Cylinder
• -0.48D0.39D (range, -1.25D to 0.00D)
• Central cornea power (EyeSys axial map)
• 42.98D0.88D (range, 40.93D to 44.92D)

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Results

• Mean values of postoperative Central Cornea Power
  (D) obtained with the clinical history method
  (RDk) and with different topographies maps

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Results

• Mean difference of each method compared with the
  RDk values

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Results

• EyeSys postop Central Cornea Power values and
  their correlation with the RDk

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Results

• Orbscan postop Central Cornea Power values and
  their correlation with the RDk

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Results

• Pentacam postop Central Cornea Power values and
  their correlation with the RDk

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Conclusions

• The EyeSys presented the most reliable values of
  the central cornea power when compared to the RDk
• However it tended to underestimate the
  refractive change (or overestimate the postop
  cornea power) as others analyzed maps with the
  exception of the Pentacam true net power and the
  Orbscan 2-mm total mean and 4-mm total optical
  power maps