Intrastromal implantation of a full corneal ring may improve vision in patients with keratoconus

J Refract Surg. 2011;27(1):63-68.

The visual function of patients with keratoconus may be enhanced through intrastromal implantation of a complete corneal ring, a study found.

Six eyes of four patients with keratoconus were treated with the corneal intrastromal implantation system (CISIS, Dioptex), a procedure centered on insertion of a flexible full-ring implant into an intrastromal pocket. Follow-up occurred at 1, 3 and 6 months.

All six eyes demonstrated statistically significant improvement for all study parameters, including uncorrected and distance corrected visual acuity, keratometry, spherical and cylindrical refractive error, and spherical equivalent refraction (P < .05). Mean uncorrected distance visual acuity improved by more than seven lines.

"The fact that CISIS, due to its significant effect on keratometry, strongly impacts the spherical component of the refractive error may be the reason why CISIS proves so efficient in improving [uncorrected distance visual acuity]," the study authors wrote.

A limitation to the study was its mixture of patients who did and did not undergo corneal collagen cross-linking. According to the authors, further studies are needed to determine if intracorneal implants in combination with corneal collagen cross-linking can replace keratoplasty, which has a higher rate of complications and requires longer recovery.