Corneal Ring for High Myopia: New Technique.

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Corneal Ring for High MyopiaNew Technique.

• Albert Daxer, Austria.
• The author is investor in DIOPTEX GmbH.

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Background

• Refractive laser surgery for high myopia may be
  vision-threatening for biomechanical reasons.
• A current alternative to laser surgery in high
  myopes is intra-ocular surgery, including clear
  lens extraction and implantation of phacic IOLs
  or ICLs.
• Implantation of intra-corneal ring segments is
  minimally invassive, however, it is either
  limited to low myopia (Intacs) or it is not
  applicable to high myopia for centration problems
  (Ferrara Ring, KeraRing).

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Corneal Intrastromal Implantation Surgery (CISIS)

• The author has developed a new kind of
  intra-corneal surgery including a new kind of
  microkeratome and a new kind of intra-corneal
  implant for the treatment of moderate and high
  myopia.
• The objectives were
• The treatment should be minimally invassive (no
  intraocular surgery, no removal of tissue, no
  weakening of the biomechanical stability of the
  cornea).
• The treatment should be reversible.
• The treatment should be quick and easy to perform
  in an outpatient procedure.
• The entire dioptic range of shortsightedness
  should be accessible.

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Corneal intrastromal implantation surgery (CISIS)

• 1st step Creation of a closed intra-corneal
  pocket using a new kind of microkeratome
  (PocketMaker). The PocketMaker microkeratome has
  CE-mark but is not approved by FDA.
• 2nd step Insertion of a new kind of
  intra-corneal implant (MyoRing) into the corneal
  pocket via a small incission tunnel. The MyoRing
  is a flexible full-ring implant which can be
  positioned easily within the corneal pocket after
  insertion. The MyoRing has CE-mark but is not
  approved by the FDA.

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Result

• The MyoRing implant in situ appears like a hard
  contact lens, however, less visible.

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Refractive results after 6 months(latest
nomogram)
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Reversibility

• The new kind of treatment is reversible.
• The spherical as well as the cylindrical
  component of the refractive error after removal
  of the implant returned almost always exactly to
  the preop value.

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Possible complications and side effects

• Decentration.
• Induced astigmatism.
• Residual refractive error.
• Regression.
• Glare, halos and night vision problems.

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Biomechanical considerations

• Cutting only parallel to the static elements
  (collagen lamellae) of the biomechanical
  framework of the cornea, which run parallel to
  the intra-corneal tension, does not result in
  biomechanical weakening of the tissue.
• If, however, the cut runs perpendicular to the
  collagen fibrils (perpendicular to the tension
  lines), the cut can weaken the cornea.

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Biomechanics LASIK vs. CISIS

• LASIK creates a flap by cutting perpendicular to
  the tension within the cornea along almost the
  entire circumference and, therefore, reduces
  both, effective corneal thickness and corneal
  stability.
• CISIS can be considered as an inverse LASIK
  procedure which do not cut perpendicular to the
  collagen fibrils (except the small tunnel) and
  does, therefore, not harm the stability of the
  cornea. It creates an almost entirely closed
  corneal pocket.

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Conclusion

• Corneal intrastromal implantation surgery (CISIS)
  is save and effective for the treatment of
  moderate and high myopia.
• CISIS is quick and easy to perform as an
  outpatient procedure under topical anesthesia.
• The procedure is reversible.
• Possible complications and side effects include
  residual refractive error, decentration, induced
  astigmatism, regression, glare, halos and night
  vision problems.
• Most possible complications and side effects are
  manageable by simple interventions.