Reader and Industry Forum
Reader and Industry Forum
Limitations of Intrastromal Corneal Rings in Keratoconus
By Bezalel Schendowich, OD, FIACLE
Over the past decade, intrastromal corneal ring implants (ICRIs) have joined the ophthalmic surgeons' battery of tools against vision-reducing conditions. Originally designed and marketed to reduce low-to-moderate degrees of simple myopia by pulling and flattening the cornea, the rings have since gained recognition by the United States Food and Drug Administration (FDA) for use in managing corneal ectasias.
At first glance, the use of ICRIs for keratoconus would seem to be an ideal application. Ectasia causes the cornea to become more prolate. By implanting ring segments, the tissue is pulled centrifugally resulting in a flattened area central to the rings—reducing the ectasia.
Unfortunately for the patients whom I have treated, the effect seems to be transitory. Keratoconic eyes typically improve after the rings are placed, but then after a period of time the corneas, which had never ceased to ectate, again show their true nature to the frustration of the patients, the contact lens fitters, and perhaps even the surgeons who implanted the rings.
Not only does the keratoconus “return,” but it does so with a passion. ICRIs require a tunnel or channel drilled or lased into stromal tissue. One description naively describes the process as placing the rings “between the layers” when, in fact, collagen fibers need to be cut in the process. This, in turn, further reduces corneal rigidity and enhances ectatility.
Unfortunately for many, ICRIs seem to have been marketed as a cure for keratoconus rather than as a tool of management as the FDA intended. Thus, patients have had the rings placed expecting an end to their suffering from deteriorating vision and uncomfortable contact lenses. This is not the clinical reality.
I have gained a unique perspective as a specialist contact lens fitter located in a referral ophthalmology clinic in a major metropolitan hospital. Patients come to us with all manner of ocular complaints and diagnoses. Our cornea clinic and, as a result, our contact lens service sees the results of others' clinical and surgical trials. Subsequently, many of our patients are not happy with the results from these other clinics and practitioners. They come to us demanding answers; in many cases, they come pleading for help.
While I acknowledge that it must be true that there are keratoconus patients who have succeeded in improving their lot with ICRIs, sadly our clinic has seen only failures. It must be for a substantial reason that our department has never “followed the herd” and instituted ICRI usage. Primum non nocere.
Complications With ICRIs
I've had the opportunity to attempt to help several patients— some who have primary ectasia and others who have secondary ectasia—who, seeking remediation for the loss of the quality of their vision, decided to undergo implantation of ring segments.
Some of the problems I have encountered with implanted corneal rings include:
• Generally, the rings are placed superficially.
• Occasionally, the ends of the rings protrude.
• Advice was not given to patients that the progression of their disease would not be halted by the rings. Thus, when their keratoconus did progress, these campers were far from happy.
• Most sad is the representation that the surgery is reversible.
This is patently not so. The rings may very well be removable, but the damage caused to collagen fibers by the insertion process cannot be undone. In fact, in the case of an ectatic cornea, an already structurally weak cornea has been further weakened in an irreversible way.
Cases in Point
The following cases illustrate the problems our patients have experienced following ICRIs.
Case 1 This gentleman in his 50s came to the clinic looking for help on two fronts. He'd had ICRIs placed (two in each eye) some five years earlier. He experienced some improvement in vision over the course of two years, but then his acuity worsened again. He also suffered from pain in his eyes that occurred nightly.
I attempted to manage his ICRI-induced problems with soft toric contact lenses, which were helpful for a time—at least for his again-deteriorating vision. When he came for follow up and reported improved vision but continued pain at night, I carefully studied his rings and found that the epithelium between the tails of the rings was eroded, and this was aggravated while he was sleeping. I advised him to lubricate aggressively at night with neutral ointments, which helped resolve the issue.
Case 2 A younger patient in his 20s followed his friends' advice and sought refractive surgery. Whether the surgeon knew of the patient's family history of keratoconus is not clear. The patient underwent laser-assisted in situ keratomileusis (LASIK), after which he developed aggressive ectasia; the same surgeon, anxious to help, implanted ICRIs, which were not only painful but induced diplopia. When the surgeon began removing the rings, the visual disturbances were exacerbated.
The case is in litigation; the surgeon, of course, offered the patient penetrating keratoplasties. The patient occasionally comes to the clinic for a follow up on his condition, but I have not encountered him for quite a while.
Case 3 This young woman had implanted rings that were so superficial, even a toric soft contact lens rubbed against them and caused her pain. She was unfortunately lost to follow up—I have not heard from her or about her for several years now.
Case 4 This young man was suffering with pellucid marginal degeneration when he had rings implanted. After the procedure, comfortable vision was obtainable only with the application of an 18.0mm mini-scleral GP lens (MSD, Blanchard), which was necessary to properly vault the rings. Any other corneal or smaller scleral design would press on the thinned and stretched corneal tissue, eroding the surface and cause him great pain.
As time has progressed and I have had the opportunity to use more advanced contact lens designs, I have begun to appreciate the value of scleral lenses in vaulting these distorted and insulted corneas. A recent case report in Contact Lens and Anterior Eye (Dalton and Sorbara, 2011) exemplifies this point and demonstrates the utility of this lens type.
Further, the article, “Fitting Keratoconus after Intracorneal Ring Implants” by Luciano Bastos in the November 2011 issue of Contact Lens Spectrum shows how a large-diameter corneal GP lens can be fashioned to vault the rings implants. In his case review, Sr. Bastos describes his success fitting these eyes with his own specially designed and modified lenses so that the vision of some keratoconus patients can be comfortably improved using contact lenses after ring insertion.
If I had had access to scleral lenses during the years when I was trying to help these patients, I am certain that all four would have ended up much happier, more comfortable, and with better vision.
A temporary fix at best, the pros and cons of ring implants need to be carefully delineated to visually compromised and psychologically stressed patients before surgery. As I have suggested, scleral lenses will most likely prove to be the ultimate remedy for the problems involved with ectasia and ICRI. The question hardest to answer in retrospect is: could we have achieved the same end without the rings? CLS
As always, I must express my respect and thanks to my patients for choosing me to help them confront the visual adversities invoked by their corneal ectasias.
For references, please visit www.clspectrum.com/references.asp and click on document #202.
|Dr. Schendowich is a Member of the Medical Advisory Board of the National Keratoconus Foundation, USA, a Fellow of the International Association of Contact Lens Educators, and an adjunct assistant clinical professor of optometry at SUNY-Optometry in the ophthalmology clinic at the Sha'are Zedek Medical Center in Jerusalem, Israel.|
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