WHAT ARE INTRASTROMAL CORNEAL RINGS?

These intracorneal devices are used to reshape the cornea.

Historically the concept of adding tissue in the periphery of the cornea to reshape it was introduced by Barraquer in 1949. In 1995 and 1999 the FDA approved the use of intrastromal corneal rings both for keratoconus and for myopia and astigmatism.

HOW DO THEY ACT?

The mechanism of action of these intrastromal corneal rings is: adding tissue in the periphery of the cornea after implantation of these corneal rings leads to flattening the cornea in the centre. This has the following consequences: corneal apex moving toward its centre, keeping corneal asphericity, reducing its irregularities.

WHAT ARE THE INDICATIONS FOR INTRASTROMAL RING IMPLANTATION?

The intrastromal corneal ring implantation is performed to correct the corneal irregularities:

  • Keratoconus
  • Pellucid marginal degeneration
  • High astigmatism
  • Correcting an irregular astigmatism after radial keratotomy (in certain topographical conditions)
  • Irregular astigmatism following corneal trauma.
  • Post-lasik ectasia

WHAT ARE THE CRITERIA FOR INCLUSION?

  • Clear cornea
  • BCVA> 0.05
  • Corneal thickness greater than 380 to 400 micron in the implantation area.
  • Keratometry <64D
  • Spherical equivalent> -3D

WHAT ARE THE CONTRAINDICATIONS?

  • Severe atopy,
  • Autoimmune disease
  • Recurrent corneal erosions
  • Extensive corneal scarring
  • Corneal dystrophies
  • Hydrops

The rings are made of PMMA, a biocompatible material, are triangular in section, have different lengths and thicknesses (customized depending on certain eye parameters of each patient).

The modern surgical techniques to implant these rings are performed using the INTRALASE femtosecond-laser.

With this very special type of laser, manual implantation shortcomings are reduced.

In the case of the implantation using laser, the corneal depth, the area of implantation, tunnel width, place of incision through which the rings are inserted, are pre-set.

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