For patients with progressive keratoconus, a new technique called small-incision femtosecond laser–assisted intracorneal concave lenticule implantation (SFII) is a less invasive and more efficient surgical procedure than penetrating keratoplasty (PKP), according to new study in Cornea.

The long-term study included 31 patients with progressive keratoconus. Twenty underwent PKP and 11 subjects had the SFII procedure. SFII involves creating a stromal pocket with a femtosecond laser into which the donor lenticule is implanted. “This technique allows for molding of implants, a minimal incision of 3.0mm and a consistent depth and thickness on every occasion,” the study says. “Therefore, this procedure does not involve any intraocular manipulations, and all surgical manipulations can be confined to a pocket within the recipient cornea.”

At one week, and one, three, six and 12 months, researchers assessed visual acuity and intraocular pressure results, and analyzed corneal topography, corneal visualization Scheimpflug technology (CST), anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy findings.

In the SFII group, vision improved in three months and remained stable for the remainder of the follow up period, and corrected distance visual acuity improved one week after surgery in the PKP group, which also remained stable through 24 months.  While both procedures affected corneal curvature, the SFII’s concave graft reshaped the cornea to be thinner centrally and thicker peripherally. “Because of greater regularization of the cornea in the SFII group, vision improved more than in the PKP group,” the study says. “This additive implantation procedure not only increased recipient corneal thickness but also increased the strength of the host cornea, as shown by CST.”

Additionally, all grafts from both groups were clearly visible on AS-OCT. SFII grafts showed no signs of increased ciliary redness or corneal neovascularization, and the graft edema decreased significantly after one month. PKP eyes had ciliary redness for a week post-op and while fresh epithelialization occurred at one month postoperatively, the graft margin still exhibited evident edema.

Researchers noted the central corneal thickness of both groups was stable during the 24-month study period, and in vivo confocal microscopy showed a few dendritic cells in the subepithelial region in the SFII group. Three months after surgery, many dendritic and inflammatory cells were found in the basal epithelium and stroma in the PKP group.

“Both SFII and PKP surgical procedures resulted in a stable corneal volume and improved visual acuity in this long-term study,” researchers said in the study. “The SFII procedure may provide a new treatment option for keratoconus in the future. Moreover, this technique may also provide new hope for the treatment of other corneal diseases.”