Referral criteria

While 80% to 85% of patients with keratoconus can be managed with spectacles, soft and rigid contact lenses to correct for visual acuity and astigmatism, in 15% to 20% of the keratoconic population, a corneal transplant is eventually required unless the patient undergoes Cornea Collagen Crosslinking (C3-R) and/or INTACS to halt the progression of disease.

Many surgeons are not aware of the less invasive Cornea Collagen Crosslinking (C3-R) developed in Dresden in the 1990s as a less invasive alternative to halt the progression of keratoconus . Patients who are referred for Cornea Collagen Crosslinking (C3-R) avoid the need for a cornea transplant in 99.0% of all referred cases.

The following are the considerations that should be made to referral for surgical management:

Cornea Collagen Crosslinking (C3-R) Referral

1) Diagnosed with keratoconus

Cornea Collagen Crosslinking (C3-R)  and INTACS Referral

1) Contact lens intolerance especially with recurrent abrasions;
2) Inability to fit the patient with a contact lens (including frequent lens loss);
3) Decreased vision (generally from scarring) which prevents the patient from doing necessary visual tasks; and
4) Large cone with progressive thinning in the periphery 

Cornea Transplant Referral

1) The danger of perforation, though rare in keratoconus.

Outcomes with Less Invasive Treatment INTACS

In most cases, the patients’ uncorrected visual acuity and best-corrected visual acuity show marked improvements.  A high percentage of these patients were candidates for an imminent transplant. The reshaped cornea, after the INTACS procedure, is typically aided by the use of glasses or soft contact lenses in order to provide improved functional vision to the patient and reduce the eye irritation previously experienced with the RGP contact lenses. 

Studies have shown that INTACS placements can restore functional vision by allowing most patients to be effectively corrected with contact lenses or glasses, if needed.  Specifically, Boxer Wachler, et. al. found that (1) the mean improvement was 4 lines UCVA and 2 lines BCVA, (2) those with less than two lines of improvement in BSCVA still improved UCVA by 2 lines or better in 60 percent of cases, (3) irregular astigmatism was reduced across the board, and (4) the number of lines of correction ranged from up to ten lines BSVCA and from counting fingers UCVA. These results were replicated by Colin, et. al., whose prospective study of 10 patients found that both BCVA and UCVA improved in more than 50% of those patients.

Researchers concluded that use of INTACS in patients with keratoconus is an effective way to manage the condition and restore functional acuity to patients.  Boxer Wachler goes farther, to say, “INTACS is to be a logical addition to the stepwise treatment of keratoconus that improves visual acuity and, in a number of patients, has negated the need for corneal transplantation, thus far.”

Surgical Treatment with Cornea Transplant

Penetrating keratoplasty (full cornea transplant) is the most common. In this procedure, the keratoconic cornea is prepared by removing the central area of the cornea, and a full-thickness corneal button is sutured in its place. An alternative is lamellar keratoplasty (partial corneal transplant); it should be noted that this alternative is used in less than 5% of cases. The cornea is removed to the depth of posterior stroma, and the donor button is sutured in place. This technique is technically difficult, and visual acuity is inferior to that obtained after penetrating keratoplasty. Its disadvantages include vascularization and haziness of the graft.

Clinical Challenges of Cornea Transplant

The eye-care practitioner must decide when to recommend keratoplasty for the keratoconic patient. This is often not a simple, straightforward decision. Keratoplasty for keratoconus is highly successful; however, there is a long recovery period and a risk of severe ocular complications. A number of factors must be considered in deciding when to do a keratoplasty. One of the most important factors is the patient’s functional vision. If the best acuity with their contact lenses prevents them from doing their job or carrying out their normal activities, or when the contact lenses cannot be worn more than a few hours a day, a transplant must be considered. The actual measured visual acuity may be quite different for different patients. One patient may find that he/she cannot do their job with 20/30 acuity while another patient may be very satisfied with 20/60 acuity.

Very careful contact lens fittings are necessary before recommending a corneal transplant. Prior to transplant every effort should be made to optimally fit the patient with contact lenses, especially if there is not significant corneal scarring affecting vision. Also, referral for less invasive procedures such as Cornea Collagen Crosslinking (C3-R) and/or INTACS.

However, a minority of patients becomes intolerant to contact lenses, and requires a transplant earlier than otherwise would be necessary. If the patient has a large area of thinning, a very decentered cone or significant blood vessel growth into the usually clear cornea, called neovascularization, a transplant may be performed earlier than otherwise indicated by the visual performance, as these factors may require a larger than normal transplant button size and/or increase the chance of rejection if allowed to advance too far.
The healing process following transplant is long, often taking a year or longer. The time from surgery to the removal of the stitches is commonly 6 to 17 months. The patient may be on steroids for months. Initially following surgery the donor button is swollen and even following healing the button is usually thicker than the corneal bed in which it rests.

Large amounts of astigmatism are common following keratoplasty. One such study found an average of 5.56 diopters of correction (DC) with a range from 0 to 17 diopters following suture removal . The patient’s spectacle prescription may fluctuate for some months following surgery. Refractive changes and keratometry or corneal topography can be used to follow the healing process.

Graft rejection reactions occur in 18% to 20% of the patients. Signs of graft rejection include ciliary flush, anterior chamber flare, keratic precipitates, Khodaoust line and Krachmer’s spots. Signs of graft rejection are reported to occur from 1 month to 5 years following surgery. The rejection rate for bilateral grafts is higher than if only one eye is grafted. In the bilateral cases, when a rejection reaction occurs it is commonly in both eyes. If the second eye is to be grafted, there is usually a period of at least a year between grafts. If signs of rejection occur, aggressive treatment with steroids is begun. Usually the reaction is overcome and the graft remains clear. A high percentage of the corneal grafts are successful. However, visual rehabilitation is slow (6 months to 1 year), and keratoconus may recur 15-20 years later in the corneal transplant. As significant, and of particular concern to younger patients, it is commonly understood and addressed in peer-reviewed literature that corneal grafts have a limited life, and that subsequent attempts to graft are less successful than the first.

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