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| Introduction:
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 0,150 mm to 0,350 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. Since then more than 2500 eyes were submitted to this procedure worldwide. FR are indicated for: 1.
Moderate to high myopias Ferrara rings are not for KC patients with cone curvature over 75D and central cornea scarring. These patients should look for corneal transplant as an option. The
Ferrara Ring implant is mostly for keratoconic patients of any age
with an evolving condition and intolerance to contact lenses or
with sharp distortions in the cornea shape, which usually occur
after transplants. 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 KC from progressing and to improve
vision acuity. |
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| The surgery is performed in a surgery room. The anesthesia is topical, by means of anesthetic eye-drops. The procedure is totally painless and lasts about 10 minutes. The utilization of antibiotic and anti-inflammatory eye drops provides a more comfortable and safer post surgery. In three days, the patient can be back to his/her normal activities if she/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. In case of any doubt, contact your surgeon. | |||||||||
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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 advantages of the Ferrara Ring implant over the cornea transplant are the following: - faster vision recovery - no rejection -
easier contact lenses fitting, if necessary
The main possible complications include:
1- Infection: Infection can occur like in any other surgeries and can be treated without need of removing rings 2- Segment migration: Usually keratoconic patients are atopic and report intense itching. Rubbing the eye may displace the segments, pushing them closer to the incisions and causing their extrusion. 3- Extrusion: It can be caused by superficial implantation or segment migration. Its occurrence can be prevented with routine examination and removal of the segment before it gets exposed and later re-implantation. This complication occurred in 3,0% of the total cases and in all of them re-implantation was possible. 4- Decentralization: The ring must be positioned at the cone basis. Therefore, the centralization procedure must be executed always considering the reflection. There was only one case of decentralization, and the procedure taken was to reposition the segments. 5- Halos and reflections: You will certainly suffer from halo and glare effect at night or even during day when you come into darker places (buildings etc.) If you want to see what is it about try this simulator: http://www.surgicaleyes.com/visual_effects/visual_effects.htm Patients who have larger pupil size will suffer more from halo effect. This effect should decrease with time and most patients report stabilization after 4-6 months. In some cases this effect will not disappear completely. Fortunately there are a lot of drops used to reduce pupil size at night and thus completely removing halo and glare problems.
Visual recovery is fast. On the following day, the vision is already better, stabilizing itself from the third month on. In that period it is normal for some vision fluctuation to occur, particularly in the morning, the patient’s vision is good, but over the rest of the day there will be a slight blurring. As it is not an esthetical surgery, it might be necessary to use eyeglasses or contact lenses to complement visual correction. However, the vision might be good, even though there is some residual refraction.
Contact address and various links:
Dr. Paulo Ferrara OD, Rua Grão Pará, 737 • 2º andar • Santa Efigênia • 30150-341 Belo Horizonte • MG • BRAZIL • Telefax: (31) 3241.6347 / 3241.2834 e-mail: pferrara@ferrararing.com.br website: www.ferrararing.com.br
Other sources and links:
Ferarra ring corneal implant by Dr. Ferrara and Dr. Lovisolo New Intracorneal Rings Segments Reduce Irregular Astigmatism in Keratoconus; First European Results
Ferrara intrastromal corneal rings for the correction of keratoconus
Ferrara intrastromal corneal ring segments for severe keratoconus.
Appendix:
Description of cone types used for Ferrara rings procedure : Cone
type I : Cone
type II : Cone
III : the
slit lamp biomicroscopy shows stromal striae, thinning of the central
or paracentral stroma, Cone
IV : |
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