Corneoplastics emerging as the newest frontier in corneal therapies

Surgeons may be able to combine conductive keratoplasty or intracorneal segments with newer techniques such as UV collagen crosslinking.

Jorge L. Alió

Emerging therapeutic corneal procedures such as ultraviolet collagen crosslinking are showing promise as possible adjunctive therapies to more familiar corneal shaping techniques such as conductive keratoplasty and intracorneal segments.

We have begun calling these procedures corneoplastics. Corneoplastics are a group of techniques, most of them coming from refractive corneal surgery, that try to modify the corneal shape with a therapeutic purpose, and they are quickly emerging as the next frontier in corneal therapies. We are creating a new environment for the treatment of diseases that were untreatable before.

Corneoplastic techniques allow surgeons to model the structure of the cornea without having to resort to invasive techniques such as penetrating keratoplasty or lamellar grafting.

We are in a moment in which corneoplastic techniques are modeling techniques that can be used in different ways in order to create better corneal optics, to create better corneal topography, to improve the optical performance of the cornea for refractive purposes. The first ophthalmologist to use the term corneoplastics was most likely Arun C. Gulani, MD, of Jacksonville, Fla. Now, this concept is spreading quickly, becoming a new subspeciality allied to refractive and corneal surgery.

Combining new and old techniques

Corneoplastic techniques can be broken down into biomechanical methods such as intracorneal segments or incisional techniques, elastic methods including ultraviolet collagen crosslinking and conductive keratoplasty (CK) and mixed methods such as excimer laser ablations or intracorneal lenses.

Some of these methods are already well known in their efficacy. Intracorneal segments, for example, are currently the best corneoplastic option for treating corneal pathologies such as keratoconus.

UV collagen crosslinking, on the other hand, is a more recent development that involves combining UV light and topical riboflavin to stimulate crosslinking among collagen fibers for increased corneal rigidity. By combining this method with intracorneal segments, the efficacy of the implants can be enhanced beyond their current capabilities.

Intracorneal segments have been used for keratoconus for more than 7 years, and these cases are more or less stable. Of course some of them were not ideal cases in the beginning. Although they did improve, some of them were followed by a residual increase in the corneal steepness because the keratoconus was advanced and was not stopped completely by the ring. At this moment the combination of UV crosslinking to these cases is adding rigidity and strength to the cornea, and stopping this process that was slowed after the rings in some cases.

Similarly, UV collagen crosslinking can be combined with CK for enhanced results. The ideal result of combining these procedures would be to marginalize procedures such as corneal grafts. You can never guarantee the outcome of a corneal grafting technique, and moreover, keratoconus may relapse on a corneal graft. This is the state of the art at this moment in the treatment of keratoconus, but it is far from ideal, far from being defined as a solution in young patients, because keratoconus may relapse in them. The most desirable situation is to find an alternative to corneal grafting.

Obstacles to overcome

While these techniques are showing promise, there is much to be learned and modified. For example, while researchers are eagerly anticipating the various applications of UV collagen crosslinking, they are also aware that UV light is toxic to the ocular structures, making it necessary to explore alternative energy options. I anticipate in the future other sources of energy will be substituted for UV light and will not be as potentially harmful.

In addition, the biomechanical qualities of the cornea pose challenges to the accurate application of combined techniques. Understanding the behavior of corneal tissue following corneoplastic procedures is complicated by its intricate structure.

Different levels of the corneal structure have demonstrated different healing capacities, meaning researchers will have to consider the multiple effects of a technique such as UV collagen crosslinking.

New diagnostic methods for corneal biomechanics

Biological structures like the cornea, even though they look simple are complex, they have different levels of collagen, the collagen fibers are a different diameter, they interweave at different angles and have a different degree of hydration.

New imaging tools such as the Ocular Response Analyzer (Reichert) are providing researchers with the means to better analyze the corneal response to these new combined techniques.

Although we are in the beginning of the understanding of this method of corneal examination, it is a new type of information that allows us for the first time to know how rigid or how elastic the cornea is.

Other methods of exploring corneal anatomy and related corneal biomechanics are important. Anterior segment optical coherence tomography (Visante OCT, Zeiss), very high frequency ultrasound such as the Artemis (Ultralink), new confocal microscopes and in the immediate future new corneal hydrometers (in the latest stage of development), will be able to measure anatomical and physical properties of the cornea that will explain better and will predict more the use of corneoplastic techniques.

The advent of these new corneoplastic and imaging techniques will hopefully give rise to many new therapeutic possibilities down the line. In my opinion we are combining these techniques, and we are beginning to understand much more what we can offer to our patients.

For more information:

Jorge L. Alió, MD, PhD, can be reached at VISSUM, Instituto Oftalmologico de Alicante, Avda. de Denia, s/n, 03016 Alicante, Spain; +34-965-150-025; fax: +34-965-151-501; e-mail: jlalio@vissum.com.