Intrastromal corneal ring segments may delay need for, provide alternative to PK

The procedure is minimally invasive, easily reversible and not restricted by factors such as graft availability.

Issue: July/August 2012

A rapid rehabilitation period and significant improvement in visual acuity, spherical equivalent and keratometry were observed after intrastromal corneal ring segment implantation in patients with keratoconus, according to a study.

The study assessed the effectiveness of the KeraRing (Mediphacos), an intrastromal corneal ring segment (ICRS) implant, in the management of keratoconus.

“The KeraRing implant is an effective treatment for managing keratoconus, and since most of the visual changes occurred during the first month postoperatively, early visual rehabilitation of these patients as soon as the first postoperative month might be reasonable,” Almutez M. Gharaibeh, MD, FAAPOS, the lead study author, told Ocular Surgery News.

Study design, results

In the retrospective case series study, 55 eyes of 43 patients with keratoconus were analyzed for uncorrected visual acuity, best corrected visual acuity, manifest refraction and keratometry. Measurements were taken preoperatively and 2 days, 2 weeks, 1 month, 3 months and 6 months postoperatively. Patients who had intraoperative or postoperative complications or who did not complete at least 6 months of follow-up were excluded.

All patients included in the study had irregular astigmatism with at least one classical clinical sign of keratoconus, clear central corneas, severely affected visual acuity, contact lens intolerance and a previous indication for keratoplasty.

Six months after surgery, mean UCVA significantly improved from 0.10 to 0.32 (P < .05), mean BCVA from 0.36 to 0.57 (P < .05), mean spherical refractive error from –4.85 D to –1.89 D (P < .05) and mean cylindrical refractive error from –3.65 D to –2.60 D (P < .05). The mean spherical equivalent decreased significantly from –6.68 D to –3.19 D (P < .05), and the mean keratometry value decreased from 51.83 D to 47.27 D.

These findings suggest that the KeraRing offers the advantage of delaying or even avoiding the need for penetrating keratoplasty, according to Gharaibeh.

Disadvantages of PK

“Patients with keratoconus are usually patients who are fed up with all types of visual rehabilitation, such as glasses and contact lenses, and are about to go for keratoplasty. This option is not easy because of the limited availability of donated grafts, especially in underdeveloped areas,” Gharaibeh said.

Various factors can limit graft availability, such as an absence of eye banks or religious and cultural factors that prohibit or discourage donors from contributing corneas, he said.

“Also, penetrating keratoplasty is a major surgery with a lot of major potential postoperative complications ranging from infections, early graft failure, early graft rejection, rejection even years after grafting and endophthalmitis,” Gharaibeh said.

ICRS implantation offers an advantage over PK because the ICRS procedure is easily reversible. In cases of unacceptable results or complications, the segments can be removed, and preoperative corneal and refractive parameters can usually be achieved after the segments have been explanted, according to the study authors. ICRS implantation also preserves the central cornea and all stromal layers and leaves the globe intact.

It may be reasonable to initiate visual rehabilitation 3 months after ICRS implantation because most of the refractive changes induced in the process stabilize by that time; however, the predictability of the procedure is low and results tend to vary, according to the study authors. – by Daniel R. Morgan

Reference:

Gharaibeh AM, Muhsen SM, AbuKhader IB, Ababneh OH, Abu-Ameerh MA, Albdour MD. KeraRing intrastromal corneal ring segments for correction of keratoconus. Cornea. 2012;31(2):115-120.

For more information:

Almutez M. Gharaibeh, MD, FAAPOS, can be reached at the Department of Ophthalmology, Jordan University Hospital, P.O. Box 13046, Amman, 11942, Jordan; email: a.gharaibeh@ju.edu.jo.

Disclosure: Dr. Gharaibeh has no relevant financial disclosures.