1. REFRACTIVE MINI FOCUS ON INTRASTROMAL CORNEAL RINGS
Ferrara Ring:
An Overview
The Ferrara Ring corrects corneal deformities and restores physiologic curvature.
BY PAULO FERRARA, MD, P H D; AND LEONARDO TORQUETTI, MD, P H D
he Ferrara Intrastromal Corneal Ring (Ferrara
T Ophthalmics, Belo Horizonte, Brazil) is a mini-
mally invasive surgical option designed to treat
ectatic corneal disorders, particularly kerato-
conus. The ring is used as an orthopedic procedure to
improve the shape of the cornea, decrease keratoconus-
The Ferrara Ring is used as an
orthopedic procedure to improve
the shape of the cornea, decrease
keratoconus-induced astigmatism,
induced astigmatism, and improve BCVA and UCVA. The and improve BCVA and UCVA.
PMMA ring segments are inserted into the peripheral
stroma, preserving the anterior prolate shape of the ante- with highly asymmetric or quickly evolving kerato-
rior corneal surface. This article provides an overview of conus are also good candidates. Other indications for
the Ferrara ring and discusses long-term clinical follow- the Ferrara device include highly irregular astigmatism
up on treatment of keratoconus with the ring. after penetrating or lamellar keratoplasty, irregular
astigmatism after radial keratotomy, and post-LASIK
CHAR ACTERI STICS AND INDICATI ONS ectasia.
The Ferrara intrastromal ring segments have a 5-mm The Ferrara Ring is not indicated for use in advanced
diameter and variable thickness, ranging from 150 µm to keratoconus with keratometry (K) readings greater than
300 µm. The ring segments, which are made of yellow 75.00 D and significant apical opacity and scarring; corneas
PMMA, have a 4.4-mm internal diameter, a 5.6-mm with hydrops; corneas with thickness of less than 300 µm;
external diameter, and a 600-µm flat base. Arc segments intense atopy (these patients should be treated before
of 90°, 120°, 160°, and 210° are available. The 210° seg- implantation); or any active local or systemic infection.
ment was most recently introduced.
The chief indication for Ferrara Intrastromal Corneal LONG-TERM F OLLOW-UP
Ring implantation is keratoconus. Patients with kerato- We retrospectively reviewed records of 340 patients
conus who have poor BCVA and are contact lens intol- (age range, 11 to 58 years) consecutively implanted with
erant are good candidates for the Ferrara Ring. Those Ferrara Ring segments. All procedures were performed by
TABLE 1. WHAT TO EXPECT FROM FERRARA RING IMPLANTATION
Keratoconus grade UCVA 20/60 or better BCVA 20/60 or better
Grade 1 59.00% 94.00%
Grade 2 53.00% 92.60%
Grade 3 30.70% 71.70%
Grade 4 19.30% 80.00%
OCTOBER 2009 I CATARACT & REFRACTIVE SURGERY TODAY EUROPE I 27

2. REFRACTIVE MINI FOCUS ON INTRASTROMAL CORNEAL RINGS
Figure 1. Characterization of patients according to
keratoconus grade. Figure 2. Patients’ pre- and postoperative UCVA.
Figure 3. Patients’ pre- and postoperative BCVA.
Figure 4. Topography demonstrates a decrease in corneal
Paulo Ferrara, MD, PhD, and the standard technique for steepness, flattening of the central cornea, and displacement
Ferrara Ring implantation was used. Patients included in of the central cornea to a more physiologic position
the study presented with clear corneas and a minimum postoperatively.
corneal thickness of 300 µm at the ring track. Patients
were contact-lens intolerant and/or showed progression alent decreased from -8.93 preoperative to -3.60 post-
of ectasia. The average follow-up was 18 months. operative (P<.001). Topography demonstrated a
Pre- and postoperative evaluations included UCVA decrease in corneal steepness, central corneal flattening,
and BCVA, slit-lamp examination, corneal thickness and displacement of the central cornea to a more physi-
measurement, and videokeratographic corneal topogra- ologic position postoperatively (Figure 4).
phy (Pentacam; Oculus Optikgërate GmbH, Wetzlar, Visual acuity of 20/60 or better was attained with
Germany). We used the Minitab software (Minitab Inc., spectacle correction in 85.2% of patients. It is important
State College, Pennsylvania) for statistical analysis. The to state that the corneal ring implant does not hinder
Friedman test was used to compare pre- and postopera- or prevent the fitting of contact lenses. Patients who
tive data. are intolerant to contact lenses preoperatively can com-
Most patients in the series had stage 1, 2, or 3 kerato- fortably use contact lenses with a better fitting process
conus preoperatively (Figure 1). Mean UCVA improved as a consequence of improvement of the ocular surface
from 20/400 preoperative (range, 20/30 to 20/400) to after Ferrara ring implantation.
20/80 postoperative (range, 20/20 to 20/800; P<.001;
Figure 2). Mean BCVA improved from 20/70 preopera- THE 210° FER R AR A R ING
tive (range, 20/20 to 20/400) to 20/40 postoperative The newest Ferrara Ring design, the 210° ring, has
(range, 20/20 to 20/200; P<.001; Figure 3). three major advantages over conventional rings: (1)
Mean K decreased from 51.85 preoperative (range, minimal induced astigmatism, (2) induced corneal flat-
33.37 to 81.03) to 47.60 postoperative (range, 31.84 to tening, and (3) implantation of a single segment. This
80.5; P<.001). Mean manifest refraction spherical equiv- ring is especially useful for the nipple type of kerato-
28 I CATARACT & REFRACTIVE SURGERY TODAY EUROPE I OCTOBER 2009

3. REFRACTIVE MINI FOCUS ON INTRASTROMAL CORNEAL RINGS
conus. The 210° Ferrara Ring is an efficient method for TAKE-HOME MESSAGE
keratoconus correction because it significantly decreas-
es keratometric values and improves UCVA, BCVA, and • Keratoconic patients with contact-lens intolerance and
spherical equivalent. poor BCVA are good candidates for Ferrara Rings, as are
We retrospectively reviewed records of 80 eyes of 76 patients with highly asymmetric or quickly evolving
consecutive patients receiving the 210° ring.1 Statistical keratoconus.
analysis included pre- and postoperative UCVA, BCVA,
spherical equivalent, and K readings. Mean follow-up • The Ferrara Ring does not preclude contact lens use.
time was 6.5 months.
Mean UCVA improved from 20/350 preoperative to • Visual rehabilitation and refractive stability are achieved by 3
20/136 postoperative (P=.001). Mean BCVA improved months postoperative.
from 20/125 preoperative to 20/55 postoperative
(P=.0001). Mean spherical equivalent decreased from loss of 1.4% per year. Considering that most patients
-5.22 D preoperative to -2.26 D postoperative (P=.050). included in the study were young, the rate of endothe-
Corneal topography showed corneal flattening in all lial cell loss was slightly higher than in normal eyes
eyes. Mean K1 decreased from 51.49 to 47.40 D (1.1%).
(P =.00014), and mean K2 decreased from 54.33 to Symptoms such as photophobia, visual discomfort,
49.14 D (P=.00022). Mean keratometric astigmatism eyestrain, and itching diminish or disappear after sur-
decreased from 3.65 preoperative to 2.69 D postopera- gery. Rubbing the eye after surgery can displace the seg-
tive (P=.0001). ments and stimulate disease progression. Rubbing could
also theoretically change the regularity of the corneal
POSTOPER ATIVE OBSERVATI ONS surface, leading to visual acuity loss.
We have observed that visual rehabilitation and The incidence of complications is low (3% to 5%).
refractive stabilization occur by 3 months after surgery. However, the rate of complications is higher in more
Generally, visual improvement is quick, and on the day advanced stages of keratoconus because the cornea is
following surgery patients usually report subjective and thinner, and pressure generated inside the stroma after
objective improvements in visual acuity. However, visual ring implantation can cause displacement of segments
acuity usually regresses within the early postoperative toward the incisions, with eventual extrusion.
weeks. By the end of the first postoperative month, the
patient typically reports that his vision was better CONCLUSI ON
immediately after surgery. The same fluctuation is As an orthopedic technique, the Ferrara Ring corrects
detected in relation to refraction and keratometry. corneal deformity and restores physiologic curvature.
After the first postoperative month, vision starts to Because the Ferrara Ring preserves the structure of the
improve, and refractive and keratometric fluctuation cornea with a low rate of complications, 95% of patients
decrease. By month 3, refraction and keratometry stabi- quickly reintegrate themselves into everyday activities.
lize. At this time, it is possible to correct residual We believe that corneal intrastromal ring implantation
ametropia, if necessary, with spectacles, rigid or soft should be formally adopted as an option for treating
contact lenses, or phakic IOLs for high myopia correc- corneal diseases. ■
tion.
Patients with central cones have a longer rehabilitation Paulo Ferrara, MD, PhD, is Director of the Paulo Ferrara
time because the central flattening process is slower. By Eye Clinic, Belo Horizonte, Brazil, and the inventor of the
comparison, patients with decentralized cones have Ferrara Ring. Dr. Ferrara may be reached at e-mail: pfer-
faster rehabilitation. We believe this is due to the disloca- rara@ferrararing.com.br.
tion of the corneal apex toward its physiologic position Leonardo Torquetti, MD, PhD, is a Consultant Ophthal-
in front of the pupil. In some cases, we have observed an mologist at the Paulo Ferrara Eye Clinic. He states that he is
increase in myopia and in K readings after ring implanta- a consultant to Ferrara Ophthalmics and has no financial
tion, caused by this same phenomenon. As the 210° or proprietary interest in the Ferrara Ring. Dr. Torquetti may
Ferrara Ring study showed, results in these types of be reached at e-mail: leonardotorqueti@yahoo.com.br or
cones, especially nipple cones, are satisfactory with this leonardo@ferrararing.com.br.
newer device.
The Ferrara Ring has a minimal effect on the corneal 1. Ferrara P, Torquetti L. Clinical outcomes after implantation of a new intrastromal corneal
endothelium. In our study, we observed endothelial cell ring with a 210-degree arc length. J Cataract Refract Surg. 2009;35(9):1604-1608.
30 I CATARACT & REFRACTIVE SURGERY TODAY EUROPE I OCTOBER 2009