Keratoconus, a progressive thinning of the cornea the tough transparent curved structure responsible for focusing 75% of the light entering the eye onto the retina is the most common corneal dystrophy in the United States, affecting one in every 1,000 or 250,000 people across all races. It typically begins during teen years and progresses at varying rates until stabilizing usually by age 45.
As the central and inferior areas of the cornea thin and gradually bulge outward, a cone-like shape is formed. This abnormal curvature changes the cornea’s refractive properties causing varying degrees of blurred vision and distortion of objects. Occasional swelling may occur which can, in time, lead to sight-impairing cornea scarring.
Similar cornea distortion and irregularity can also be seen in certain eyes that had Radial Keratotomy, LASIK induced ectasia or trauma.
The treatment for keratoconus occurs in stages, from spectacles to contact lens to surgery typically over many years. Visual quality can initially be restored with spectacle correction or soft contact lenses. If the condition is detected early enough, corneal cross-linking is a promising option, currently in US FDA trials, designed to stiffen the cornea and stop it from gradually deforming. More advanced stages require rigid contact lenses. A proper contact lens fit is crucial to insure optimal vision and comfort. In time, the cornea may become so warped, that contact lenses may repeatedly fall out of the eye or cannot be tolerated because they are too uncomfortable to wear.
At this point, INTACS can be considered. These are two semicircular small plastic devices that are threaded into the cornea adding support and making the curvature more regular. In many cases, vision is improved and contact lens tolerance is increased.
Intacs® are tiny (0.25mms thick) acrylic ring segments (see figure above).
Intacs® inserted within cornea (see figure above).
Historically, cornea transplantation has proven to be a successful treatment option for advanced keratoconus although INTACS may delay this option indefinitely. However, in later stages vision is so poor that corneal transplantation may be inevitable. Even after a transplant, glasses or contact lenses are usually required and visual rehabilitation may take many months to achieve. Although keratoconus rarely results in total blindness, 20% of all patients will eventually require a corneal transplant.
Richard A Erdey, MD is a Corneal Specialist in Columbus for over 20 years. Since 2007, he has been devoted to advancing new innovative methods that do not require traditional full-thickness corneal transplantation. Now, only the deficient layers may be removed and replaced with the same layers from the donor cornea. Drs. Erdey, Kaswinkel and their team currently perform Deep Anterior Lamellar Keratoplasty (DALK) in nearly 100% of keratoconic and lasik induce ectasia patients who require corneal grafts. Unlike full-thickness transplantation, this elegant partial-thickness corneal transplant preserves the TWO extremely thin, inner-most layers of the cornea: Descemet’s membrane and the endothelium, while removing only the diseased, weakened or scarred anterior layers and replacing it with donor tissue. If the endothelial layer is normal, then it is worth preserving because donor endothelial cells have dramatically shortened longevity and may subsequently be rejected by the immune system. Avoiding graft failure due to either of these reasons is very important because when the endothelial cells fail, the cornea clouds, vision deteriorates and a new graft may be required.
Retention of this important layer not only may permit a DALK graft to last a lifetime but also makes the creation of larger diameter grafts possible. Drs. Erdey and Kaswinkel have developed techniques which permit the creation of larger diameter DALK grafts which tend to have less astigmatism and optical aberration and are associated with more rapid optical rehabilitation than smaller diameter grafts.
Read: Large-diameter DALK technique minimizes post-operative astigmatism – Richard A. Erdey, M.D.
At this time, very few cornea specialists offer this extremely delicate, time-intensive and poorly reimbursed procedure despite its many benefits. In fact, only 751 DALK’s were performed in the USA in 2012. Another 18,000 eyes had full-thickness traditional corneal transplants when in retrospect the vast majority may have been suitable DALK candidates! Dr. Erdey is a frequent speaker at local and national conferences and passionately believes broader surgeon acceptance of DALK will eventually occur.