Surgeries
Keratoconus
Eye Disease
Ferrara rings (FR) are intrastromal
segments implanted into patient's cornea tissue. FR
is composed of two 5mm-diameter semicircular segments
with variable thicknesses ranged from 0,15 mm to 0,35
mm. The ring is made of Perspex CQ Acrylic, which is
the same material used for more than 20 years in manufacturing
intraocular lenses. The ring is perfectly tolerated
by the organism and there is no risk of rejection. First
FR for keratoconic patient were implanted in 1996.
The advantages of the Ferrara
Ring implant over other surgical procedures that act
on the cornea are the following:
• Operation is done under
topic anesthesia;
• Faster vision recovery;
• Reversibility: the ring can be removed and the
cornea reassumes its original dimension from before
the Implant;
• Readjustment: the ring can be substituted or
replaced if it is necessary to improve the results obtained;
• Stability: the results are kept for a long term;
• Prevision: the results are reproducible;
• Preserves the organ integrity, as it is an addition
technique, preserving the noble region of the cornea,
that is the visual axis;
• Preserves de corneal positive asphericity, which
is an important optical characteristic in reducing aberrations
of the system and in permitting a better visual acuity.
The correct indication for the Ferrara Ring implant
requires a complete evolution of the cornea topographical
and pachymetric conditions, besides the complete ophthalmologic
exam. The main purpose of FR is to reshape the cornea
and thus reduce astigmatism, to reinforce and stabilize
the cornea and possibly delay or prevent keratoconus
from progressing and to improve vision acuity. Generally,
the Ferrara Ring implant can be recommended cases such
as these:
• Patients with keratoconus
who are contact-lens-intolerant;
• Patients with a keratoconus in evolution;
• Corneal war page;
• Astigmatism after penetrating keratoplasty;
• Corneal ectasia iatrogenic after refractive
surgeries. (PRK, LASIK);
• Irregular astigmatism after radial keratotomy;
• Pelucid marginal degeneration.
The Ferrara ring acts according to Barraquer´s
and Blavatskaya´s postulate. According to them,
a tissue addition in the cornea periphery results on
its flattening down, and the ring diameter determines
by how much the cornea will be flatten down. Thus, the
more tissue is added (ring thickness) and the smaller
the diameter, the bigger the flattening and the myopic
correction obtained.
The surgery is performed in a
surgery room. The anesthesia is topical, by means of
anesthetic eye-drops. The utilization of antibiotic
and anti-inflammatory eye drops provides a more comfortable
and safer post surgery. In three days or even earlier,
the patient can be back to his normal activities if
he has necessary vision acuity.
Reviews should start the day
following the surgery and continue in the 1st, 3rd,
6th and 12th months and then once a year. Normal symptoms
immediately after surgery are pain, teariness, photophobia
(aversion to light) and eye redness, "feeling sand
in eye", feeling the presence of the rings are
normal symptoms after surgery. However, the later occurrence
of those symptoms is abnormal and the doctor should
be immediately informed.
The success rate is directly
proportional to the keratoconus severity level. Thus,
the earlier the surgery is performed the greater is
the chance of success, which in early stages is 95%.
The procedure is totally painless
and lasts about 10 minutes.
