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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
2. High myopic astigmatism, simple or compound
3. Irregular astigmatism: In keratoconus and also after corneal transplants

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.

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
- reversibility
- disorder evolution is stopped or delayed for undetermined time

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:

Stage III or IV keratoconus may benefit from central cornea flattening by Ferrara ring segments

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 :
Patient shows mild visual discomfort
BSCVA 20/30 or worse
Slit lamp examination shows an increased visualization of the nerve fibers and the endothelium reflex is increased;
There is a break of the keratometric mires and the K reading is up to 48 D

Cone type II :
The visual discomfort is increased
Patients refer eye pain, BSCVA 20/50 or worse
The keratometric signs are more evident, and the K reading is up to 52 D, in addition to the signs referred for the cone I

Cone III :
The visual acuity is 20/60 or less,

the slit lamp biomicroscopy shows stromal striae, thinning of the central or paracentral stroma,
Keratometric reading is between 54 D and 58 D

Cone IV :
The BSCVA is less than 20/200
Cornea shows marked opacities and sometimes Descemet ruptures, an important thinning at the apex of the cone.
The corneal curvature is bigger than 60 D, and contact lens fitting is almost impossible