Information about a stage related therapy that we propose:

For the last 15 years we are working on conventional and surgical therapy of keratoconus. We have come to the conclusion that the present customary suggestion to use contact lenses up to the last stage of the disease is not substantiated and should no longer be recommended.

This recommendation is meant to help patients to bridge the problems of their initial keratoconus to the stage III or IV. A penetrating keratoplasty must then be performed. The problem of this treatment is, that the endothelium of

the donor button which is the most important layer of the cornea - as it feeds the cornea with oxygen - degenerates within a few years. The frequency of re-operations after 10 years reaches more than 50% (The Australian Corneal Graft Registry 2004 Report, research on 11.000 operations). Numbers cited there correspond to our experience on 4.000 corneal transplants carried out here. The disease is not healed by the transplantation of a donor cornea in full thickness, which may only lead to a temporary improvement.

In almost all of the Keratoconus patients the endothelium is healthy and should be preserved. Any possible healing of the

disease can only be achieved by maintaining these patient's own internal layers. Therefore we think that suggestions that postpone a disease-stopping therapy are no longer justifiable.

Goal of the stage-related therapy therefore is to maintain the patient's own cornea.

There are the following possibilities:

Under the prerequisite of staging the disease like shown in the following table, we recommend for stage I and II the procedures that bring the cone into a standstill.

Circular Keratotomy (CKT) is a trephine cut into he patient's own cornea with the Guided Trephine System (GTS).

Prerequisite for the use of this technique is a thickness of >450µm at the site of the incision of a 7mm trephine around the optical axis. With the instrument the cornea is fixated with a special suction ring and the inner surface is rounded within the trephine. The cut is then performed to 90% of the depth of the cornea as measured with Orbscan.(Fig.1)

Aim of the procedure is to create a circular scar that creates millions of

connecting tissue fibres. We have noted in 91% a complete stop of any steepening of the corneal radii (K-Readings), which would occur typically with the progression of Keratoconus. In 50% visual acuity improved. We have 230 cases 66 of which are consecutive cases over a period of seven years.(Fig.2)

Also topographies - surface images of the cornea 6 years apart - show stability (Fig.3)

In many cases not only stability, but improvement of the central area can be observed. (Fig. 4)

Depending of the thickness of the corneal tissue in addition to the cut a Titanium ring may be placed in the wound to stabilize the cornea. (Fig.7)

The procedures described are procedures for Stage I or II. If the cone is progressed further, the scar generated is not strong enough to stop the progression of the disease.

Publication:

Circular Keratotomy to Reduce Astigmatism and Improve Vision in Stage I and II Keratoconus

Epikeratophakia:

A procedure performed together with CKT is the application of an Epikertophakia (Epi).

This is a corneal lens produced from human donor cornea which is carved to the refractive values of the patient with the Excimer-Laser. It is a living contact

lens custom-made for the given situation of the patient. This procedure is especially useful for patients in which Keratoconus has caused a high shortsightedness or astigmatism or a combination of both. (Fig.5)

Publication:

Live Epi for Keratoconus

 

In case there is no high shortsightedness or astigmatism or if the tissue, is too thin to create a firm scar, we recommend Deep Anterior Lamellar Keratoplasty (DALK).

With his operation only the diseased cornea is removed in an area of 8mm diameter down to the posterior layers. The latter include Descemet's membrane and the one layered endothelium, both of which must be healthy as is generally the case for those layers up to the latest stage of the keratoconus. The patient's own endothelium is preserved and will stay for his lifetime.

DALK is a permanent procedure that heals Keratoconus. (Fig.6)

The success rate for DALK is about 93%. For the success of this operation Descemet's membrane must be bared - freed of all adjacent tissue. This in some instances may not be possible - be it due to overstretching of the tissue by steep cones or by scars - they adhere firmly and cannot be removed. In about 5% the posterior layers open spontaneously so that one has to convert to a penetrating keratoplasty during operation.

A permanent healing cannot be achieved if a penetrating keratoplasty (PKP) because the transplant's lifetime exceeds rarely 10 to 15 years. The additional problem of PKP is the occurence of immune reactions in 6% of the cases. This reaction only occurs in 1% with DALK.

Publication:

Deep Anterior Lamellar (DALK) vs. Penetrating Keratoplasty (PKP): A Clinical and Statistical Analysis

 

(click to view the abstract at "Klinische Monatblätter" - the publication is in german)

In stage IV - if the patient has waited too long and the posterior layers are scarred or overstretched - a DALK is no longer possible.

Then a PKP must be performed. In these cases we implant a titanium ring to minimize irregular astigmatism, which is common in PKP (Fig.7)

DALK's in Germany are only performed in very few clinics. The argument for not doing this procedure is that visual acuity match PKP. This in our patients is not the case. The statistic shows that the optical result of DALK is as good as in PKP. Our statisitics wih high case numbers show identical results of outcomes of both visual acuity and cylinder in DALK vs PKP. (Fig.8)

A further procedure to stop keratoconus - aside from CKT (s.a.) - is cross-linking (CL) with Riboflavin. This procedure does not improve visual acuity but freezes the situation of the cone such as presented. Prerequisite of CL is thickness of more than 400µm over the whole cornea. It can therefore only be used for Stage I+II.

Cost of CKT are not reimbursed by the social insurance companies. DALK and PKP are standard procedures which are reimbursed. Refractive Epi will not be overtaken by social, but by private insurances. Riboflavin cross-linking will be paid by some social and private insurances.