There are no drugs known to reverse or prevent keratoconus, but patients may be able to slow its progression by refraining from rubbing their eyes. When spectacles or contacts are no longer effective, there are several surgical options, including the following:
Penetrating keratoplasty. Full-thickness penetrating keratoplasty (PK) is the treatment most commonly offered. Nearly 95 percent of these procedures maintain a clear and functioning graft at five years. The rejection rate appears to be lower than that seen in patients undergoing PK for other indications. In spite of successful surgery, residual corneal astigmatism and refractive error often limits the corrective power of spectacles and usually requires additional correction with a contact lens. In addition to irregular astigmatism, complications after PK can include allograft rejection, a fixed, dilated pupil and, on occasion, recurrence of keratoconus. What causes recurrence is unclear; it may represent underlying disease in the donor or possibly progression of disease.
Lamellar keratoplasty. For patients who have moderate keratoconus without significant scarring, there is renewed interest in lamellar keratoplasty, especially with the precision, predictability and convenience of the femtosecond laser for these cases.
Corneal ring segments. Corneal stromal ring segments (Intacs, Addition Technology) are also an option, particularly if the patient demonstrates disease progression with apical displacement. These ring segments consist of two 150-degree PMMA arcs that are inserted surgically into the cornea through a small 1.8- to 2-mm radial incision created in the steep axis. Adding ring segment thickness to the midperipheral corneal stroma produces an “arc shortening,” effectively flattening the central cornea. This results from the corneal lamellae extending from limbus to limbus in a continuous fashion with a new alteration in corneal curvature that is in proportion to the ring thickness. The thin, ectatic, keratoconic cornea is particularly amenable to this effect.
Complications have primarily been associated with the insertion technique, but technique has improved greatly due to the use of new equipment designed to reduce the risk of poor ring placement. Although the ring segments lack great predictability, most properly selected patients experience some improvement in their uncorrected vision and may regain contact lens tolerance due to improved corneal topography.
Recent studies have shown that Intacs corneal ring segment implantation is a safe and effective treatment for keratoconus, with significant and sustained improvements in vision as well as improved contact lens tolerance.2 Studies have also compared placement of single-ring with double-ring segments. In some cases, the single-ring segment offers improved astigmatic correction, but the evidence is not conclusive.3 Studies are also under way examining the combination of ring segments with collagen cross-linking using riboflavin activated by ultraviolet irradiation.
Contraindicated surgeries. LASIK remains contraindicated in patients with keratoconus due to the possible risk of accelerating the ectasia. Surface ablation photorefractive keratectomy procedures are also considered contraindicated in patients with known keratoconus; however, this surgery is currently under study in patients with early disease that is considered stable or slowly progressive.