Keratoconic eye experience with a long-arc intrastromal corneal ring

Until quite recently, patients with keratoconus faced a somewhat bleak future. Patients whose vision could no longer be managed with spectacles and rigid contact lenses typically faced highly invasive penetrating or lamellar keratoplasty and the side effects and postoperative complications associated with these procedures.

Thankfully, this is no longer the case. There are now several treatment options available including toric phakic IOLs, collagen corneal crosslinking, topo-guided photorefractive keratectomy (PRK) and intrastromal corneal ring segments (ICRS). Although some patients may still eventually require a corneal transplant, these treatment modalities can at least delay, if not negate, the need for keratoplasty.

In patients with early-stage keratoconus, ICRS implantation can help to improve visual acuity by decreasing irregular astigmatism and reducing corneal steepening.¹ ICRS are appealing to both surgeons and patients because the surgery required is minimally invasive and because they can be removed or repositioned if necessary. Importantly, they can be successfully combined with other treatments such as corneal crosslinking and PRK in patients with more advanced keratoconus, which can optimise the effects of the ICRS.^2-6

Although ICRS may be associated with complications such as incomplete channel creation and postoperative segment migration, I regard it as a core treatment in the management of keratoconus.

Long-arc ICRS

Long-arc ICRS

There are numerous commercially available ICRS. These include the Intacs and the Ferrara ring (Ferrara Ophthalmics, Belo Horizonte, Brazil), and the Keraring (Mediphacos Ltda, Belo Horizonte, Brazil).

ICRS selection depends largely on surgeon preference. In my own practice, I regularly use the Keraring because it is available in two models (SI-5 and SI-6) for implantation in 5.0, 5.5 and 6.0 mm optical zones, and in a variety of thicknesses (from 150 μm to 350 μm) and arc lengths (from 90° to 355°), allowing me to precisely tailor treatment according to my patient’s needs.

Also, the Keraring was specifically designed for corneal ectatic disorders and incorporates a unique prismatic design that helps to reduce the incidence of glare and haloes.

The newer, longer arc lengths (340° and 355°) were designed to aid central corneal flattening; they are mainly used in patients with central (nipple-type) keratoconus.⁵

Because the 340° and 355° Kerarings have become available only recently, there are few published data describing refractive and topographic outcomes in patients implanted with these longer arc lengths.

Clinical findings

Clinical findings

I recently performed a retrospective analysis to evaluate the visual and refractive outcomes following femtosecond-laser-assisted Keraring 340° (300 μm or 200 μm thickness) implantation in patients with keratoconus. Forty-eight eyes of 38 patients (mean age 25.6 years [range 14–43 years]) were evaluated. All types of keratoconus – not only nipple-type keratoconus – were included in the analysis. Outcome measures included uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction sphere, cylinder, keratometry and corneal topography.

At an average follow-up of 6 months (range 3–18 months), mean UCVA and mean BCVA (LogMAR) were 0.65 and 0.32, respectively, versus preoperative values of 1.19 and 0.55. There were also marked reductions in mean sphere (–1.95 postoperatively versus –5.17 preoperatively) and cylinder (–2.46 postoperatively versus –4.68 preoperatively).

There was a reduction in all keratometry values. The mean K value was reduced from 49.18 D preoperatively to 44.74 D postoperatively, indicating a mean reduction of 4.44 D after Keraring implantation. Reductions in mean K1 and K2 were also noted (Figure 1).

No patients experienced complications.

(FIGURE 1) Keratometry values before and after keraring implantation.

Overall, findings from this 48-eye retrospective analysis indicate that femtosecond-laser-assisted ICRS Keraring 340° implantation is an effective and reliable procedure for the visual rehabilitation of keratoconus patients. In this study, the Keraring 340° improved UCVA and BCVA and reduced astigmatism and keratometry.

Comparative findings

Comparative findings

As noted earlier, because the Keraring 340° has been available only for a short time, there are few other studies describing outcomes following implantation of this ICRS. A prospective 11-eye study by Efekan Coskunseven, MD, in patients with advanced central or paracentral zone keratoconus who were implanted with the Keraring 340° also showed improvements in UCVA, BCVA, cylindrical refraction, spherical equivalent and mean K.⁷ Similarly, in a 12-eye study by Rodrigo Teixeira Santos, MD, there was a statistically significant improvement in uncorrected distance visual acuity and a (non-statistically significant) improvement in corrected distance visual acuity after 6 months. Dr Santos’ study also showed statistically significant improvements in sphere, cylinder and spherical equivalent and keratometry values (mean K, K1 and K2) at 6 and 12 months. Significant improvements in mean astigmatism and asphericity were also noted at both follow-up visits (unpublished data). Overall, data from both of these studies are consistent with the findings from my own retrospective analysis.

It is clear that larger studies with long-term follow-up across a spectrum of keratoconus patients are needed to fully evaluate the efficacy of long-arc ICRS. However, findings from my own study demonstrate that the Keraring 340° is an effective and reliable method of visual rehabilitation that should not necessarily be restricted to use in patients with nipple-type keratoconus.

At a glance

At a glance

• ICRS help to reduce refractive errors, improve visual acuity and regularise the corneal surface in patients with keratoconus

• ICRS with a longer arc exert greater flattening effects on the central cornea, better addressing the needs of patients with central, nipple-type keratoconus compared with shorter-arc ICRS

• Findings from this 48-eye retrospective analysis indicate that femtosecond-laser-assisted ICRS Keraring 340° implantation is an effective and reliable procedure for visual rehabilitation in all forms of keratoconus, from mild to severe and in different topographical types

• The Keraring 340° improved UCVA and BCVA and reduced astigmatism and keratometry

References

1. A.M. Gharaibeh et al.,Cornea 2012; 31(2): 115-120.

2. G.D. Kymionis. Open Ophthalmol. J. 2011; 5: 10.

3. C.C. Chan, M. Sharma and B.S. Wachler. J. Cataract. Refract. Surg. 2007; 33(1): 75-80.

4. E. Coskunseven et al., J. Cataract Refract. Surg. 2009; 35(12): 2084-2091.

5. G.D. Kymionis et al., Am. J. Ophthalmol. 2011; 152(5): 748-755.

6. A.J. Kanellopoulos and P.S. Binder. Cornea 2007; 26(7): 891-895.

7. E. Coskunseven. Presented at the 19^th ESCRS Winter meeting, 2015.

Dr Delso Bonfante and Dr Fernando Bonfante
E: delso@clinicabonfante.com.br

Delso Bonfante, MD, is the founder and clinical director of Clínica de Olhos Delso Bonfante, Chapecó, Brazil. Fernando Bonfante, MD, is a corneal specialist at the medical school of the Holy House of São Paulo, Brazil. Drs Delso and Fernando Bonfante state that they have no financial interests in Mediphacos Ltda.