Keratoconus - Degenerative Eye Disease
Alternative Treatment Options for Corneal Thinning Disorder
Sep 16, 2009
Keratoconus is a degenerative thinning disorder of the cornea. The affected tissue progressively weakens and conically bulges outward. This creates varying degrees of irregular astigmatism that has proved extremely frustrating to treat and manage.
Current Treatment Options for Keratoconus
Traditionally, Rigid Gas Permeable contact lenses (RGP’s) and Penetrating Keratoplasty (Corneal Transplantation) were the mainstays of Keratoconus treatment. More recently, however, high performance soft toric, piggyback, soft perm and scleral lenses have been introduced. The surgical implantation of Intrastromal Intacs, Ferrara Rings and Phakic/Toric Contact Lenses have also found favour with certain Specialists.
The extremely delicate nature of a keratoconic cornea has meant that some of these options have fared better than others; invariably, it is the patients themselves who provide or deny them credit. Each case is specific and no two corneas are alike; therefore standardizing treatment in search of a cure may not be the answer.
New and Innovative Approaches to solving the Keratoconus riddle
An eye clinic in Rome, Italy, is adding to the above list by offering an array of new, and not so new, alternate treatment options.
Asymmetric Radial Keratotomy – Mini A.R.K
Mini A.R.K should not be, but often is, confused with its predecessor, R.K. (Radial Keratotomy). It is a specialized surgical procedure in which micro-incisions are placed on the cornea in such a way as to flatten and strengthen its irregular curvature.
The origins of the method stretch back many years but the man who had most influence on mini A.R.K’s heritage was celebrated Russian Ophthalmologist, Svyatoslav Fyodorov - modern father of Radial Keratotomy.
A long time student of Fyodorovs’, Prof. Massimo Lombardi, would evolve the process and adapt it to specifically target Keratoconus. After many years of trial and technical refinement, an asymmetric ‘mini’ technique was envisioned. Fyodorovs’ R.K had to adapt to contend with the variation and irregular corneal thicknesses that are endemic to Keratoconus; the incisions were reduced in length and restricted to the central optical zone.
Each cornea was carefully scanned and a detailed map, a blueprint for the incisions to come, was created. The procedure is patient-specific and, as such, requires adhesion to a detailed inclusion criteria and pre-surgical analysis. It is an outpatient style procedure performed under local anesthesia that lasts approximately 1-3 minutes per eye.
Selective Asymmetrical Cross-Linking
A new treatment that has shown real success in the war against Keratoconus is Corneal Collagen Cross-Linking. Pioneered by Professors’ Theo Seiler and Eberhard Spoerl, it has proven an extremely simple, minimally invasive procedure.
Cross-linking works by targeting the collagen ‘strands’ that form the cornea’s structural matrix. Riboflavin eye drops are administered to the corneal surface and are, in turn, treated with a beam of ultraviolet light. The Keratoconic cornea’s weakened collagen fibrils lose their ability to link; hence the bulging effect. Cross-Linking seeks to re-establish these connections so as to restore the cornea’s strength and prevent the progression of the disease.
The Lombardi Eye Clinic has taken this procedure and, again, pushed it in new directions. Selective Asymmetrical Cross-Linking employs ‘masks’ to further focus its effectiveness - these are in the form of contact lenses with varying areas blocked; thereby exposing the cornea to a more select feed of UV light.
Differences between the two methods: SACL and traditional Cross-Linking
- SACL does not require the removal of the epithelium
- It employs a selective asymmetric surgical protocol, also true of any micro-surgery used in conjunction with SACL
- SACL can be performed on corneas that have reached 400 microns (ascertained with a pachymeter before treatment commences), the minimum thickness required to guarantee a treatment free of undesired side effects. Many patients reached this minimum pachymetric value by inducing artificial edema prior to treatment or by repeatedly using anesthetic eyewashes, riboflavin and vitamin C for a prolonged period
- SACL uses corneal lenses (masks) to specifically restrict the area of treatment
- SACL requires maximum myosis during treatment
Mini-Selective Asymmetrical Radial Keratotomy (Mini-SARK)
Mini-SARK is another innovation that seeks to focus its effectiveness. It reduces the number of incisions used in mini A.R.K and further restricts the area of treatment. It is sometimes used prior to performing the Selective Asymmetrical Cross-Linking (SACL) treatment. As mentioned, SACL differs from traditional Cross-Linking by not requiring the epithelium to be removed. Instead, SACL uses the incisions made during mini–SARK to transport Vitamins B and C deep into the collagen matrix.
Glossary of Terms:
- Astigmatism - Impaired eyesight resulting usually from irregular conformation of the cornea
- Toric - A type of lens whose surface is a combination of a sphere and a cylinder.
- Phakic - An intraocular lens (IOL) an implanted lens in the eye, usually replacing the existing crystalline lens
- Intrastromal - Within the stroma or foundation substance of any organ or part
- Keratotomy - Surgical incision into the cornea
- Epithelium - The outermost layer of cells of the cornea
- Pachymeter - A medical device used to measure the thickness of the eye's cornea
- Myosis - Constriction of the pupil of the eye
- Collagen - An insoluble, fibrous protein that is the main component of connective tissues in the body
Related Articles:
Eye Exercises and Vision Training
Maintaining Eye Health against Disease
Sources:
Attacking Keratoconus Selectively & Effectively - Massimo Lombardi, MD & Patrizia Belilli, MD
The Global Keratoconus Foundation - Worldwide Keratoconus Patient Support
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