Clinical results: long-term follow-up in keratoconus

We retrospectively reviewed patient records of 94 eyes of 76 patients, which were consecutively operated (Ferrara Ring implantation). Patients were intolerant to contact lens and/or showed progression of the ectasia.

All patients completed at least a 2 years follow-up. No intra-operative complications occurred during the procedures.

Mean keratometry decreased significantly from the preoperative to the last postoperative follow-up. The topography showed a decrease in the corneal steepening at the postoperative period, flattening of the central cornea and displacement of the central cornea.

As showed in previous studies, the intrastromal ring flattens the cornea and keeps this effect for a long period of time. There is no significant re-steepening of the cornea over time.

The present study showed that the Ferrara ring can be a valuable tool to provide topographic and visual stability, delay the progression of keratoconus and postpone a corneal grafting surgery to more physiological position.

Clinical results: the 210 ferrara ring

The 210-degrees of arc Ferrara intrastromal ring (210-FICR) has 3 major advantages over the conventional ring: 1) minimal astigmatic induction; 2) corneal flattening and 3) implantation of a single segment. This ring is especially useful for the nipple type of keratoconus. The 210-FICR is an efficient method for keratoconus correction, significantly decreasing the keratometric values, spherical equivalent and improving UCVA and BCVA.

We retrospectively reviewed patient records of eighty eyes of 76 patients, which were consecutively operated, in which the 210-FICR was implanted. The mean follow-up time was 6.65 months. Corneal tomography (Pentacam®) showed corneal flattening in all eyes.

Clinical results: post-refractive surgery corneal ectasia

Twenty-five eyes of 20 patients with corneal ectasia who underwent Ferrara intracorneal ring segments (ICRS) implantation were included in this study. The mean follow-up time was 39.8 ± 21.1months.

Our postoperative results show a significant improvement in UDVA and CDVA. Moreover, there was significant increase in corneal thickness. We found a significant decrease in asphericity values after implantation of ICRS in this study.

The keratometry values reduced significantly in all eyes. It can be realized that the mean preoperative values are usually lower than ones found in keratoconus (primary). This can be explained somewhat by the corneal flattening induced by the refractive procedure, usually in an optic zone of greater extent than the location of the ectasia.

The potential advantages of ICRS implantation over keratoplasty in eyes with post-LASIK ectasia are many. First, it avoids further laser treatment, eliminating central corneal wound healing. This leaves the optical center of the cornea untouched, enhancing the refractive outcome. Second, the technique is reversible in cases of an unsatisfactory refractive or clinical outcomes and minimal postoperative care is required. Third, adjustment can be performed using thinner or thicker rings. In cases of unexpected corneal shape changes, 1 segment can be removed or exchanged. Fourth, it avoids the complications of intraocular surgery.

Clinical results: endothelium evaluation

We retrospectively reviewed patient records of 102 eyes of 81 patients, which were followed for a period of at least 1 year. All patients had the diagnosis of keratoconus, post-LASIK ectasia or pellucid degeneration. Statistical analysis included preoperative and postoperative keratometry and endothelial characteristics.

All corneas remained clear during the follow-up period.

There was significant corneal flattening as showed by keratometry changes.

Endothelial cell loss after penetrating keratoplasty is known to be an ongoing process even years after surgery. It is well known that the cell loss is higher in the early time course after surgery and decreases 3-5 years after surgery. There is great variation of rates of cell loss after PK at the long-term follow-up. Even after DALK, which is a surgical technique that spares the receptor endothelium, cell loss has been reported.

Our study suggests that some endothelial changes occur after Ferrara Ring implantation. However, these changes are minimal and non-clinically significant, since the endothelial cell loss rate is not much higher than the normally expected for normal corneas. In contrast, the long-term endothelial cell loss after other therapies for keratoconus is much higher (as in PK, or even DALK, in which the receptor endothelium is spared) or unknown (as in cross-linking).

Contact lens wear after Ferrara ring implantation

Contact lens wear in keratoconus patients can be considerably facilitated after Ferrara ring implantation. Once there is corneal surface regularization with reduction of the excess of prolatism, the majority of patients can be well fitted with contact lens after the surgery.

The contact lens trial must be done only after 3 months of surgery, which is the period required for keratometry and refraction stabilization. It is very common that patients that usually were intolerant to rigid gas-permeable contact lens in the preoperative period become tolerant after the surgery. It is frequently possible to fit soft contact lenses in these patients. Moreover, there is very good stability of the contact lenses after the surgery, with “losses of lenses” caused by instability (a common complaint before the surgery) not occurring anymore.

Complications

The incidence of complications after the learning curve is very low. Postoperative complications can be related to: 1) the surgical technique, 2) the nomogram and 3) the ring itself. The complications related to the surgical technique are: extrusion (due to a shallow tunnel), infection, bad centration of the segment (wrong placement of the ring), migration and misplacement or asymmetry of the segments.

The complications related to the nomogram are linked to the corneal biomechanics, and can be: 1) overcorrection and 2) undercorrection. Although the predictability of postoperative results is high, in some cases overcorrection and undercorrection can occur due to viscoelastic and biomechanics profile of the different keratoconic corneas.

The complications related to the ring itself are: 1) halos and glare, 2) periannular deposits and 3) neovascularization. Halos are reported by 10 % of patients and can be related to the pupil size. This symptom tends to fade or at least diminish over time. Neovascularization of the stromal tunnel is rare, and usually occurs in atopic patients. We have used subconjunctival Bevacizumab to treat this complication, with reasonable results, as reported by the literature.

New trends

• Invisible Ring - Reduce the refraction index of the ring to achieve the same corneal Index.
• Intelligent Ring - To measure the cornea changes.

New research

• Corneal Biomechanics
• New Biomaterials that resemble the cornea

Partners

• Universidad Buenos Aires
• Susana Marcos