In people with keratoconus, until a few years ago, we had no choice but to replace all three layers of the cornea to correct their problem. This was a good option, called a corneal transplant. It involved using a small round blade to cut out the central thin part of the cornea. Success rate has been excellent, with most people improving vision to 20/40 or better after surgery. Yet in keratoconus and other corneal problems, affecting the outer layers of the cornea, it was a shame to have to remove the normal, inner layer of the cornea. This thin layer works as the water pump, pumping out the excess fluid from the cornea. It is also the layer that is most likely to reject, if a transplant rejection should occur. So why not retain this layer? With recent, modern techniques this is now possible to do by splitting the cornea between the middle and inner layer. This can be done with a special instrument called a dissector, by using air or fluid to separate the layers, or by means of a laser. This preserves the integrity of the eye by only replacing the layers of the cornea that are affected most, being the middle layer. This is a big advance for people with keratoconus, giving vision equivalent to that obtained with an all-layer corneal transplant with a much reduced risk of rejection.

It is more exacting surgery, we are splitting the cornea (a half millimeter thick membrane) at the 95% depth. Sometimes the dissection is incomplete or too deep, if this occurs, a standard corneal transplant is done instead. This is still an excellent option for people with keratoconus with a great success rate.

In summary, DALK offers another option for patient with keratoconus that are too advanced to benefit from Contact lenses or Intac ring inserts.