Introduction – Keraring, MyoRing and Ferrara Rings
The first step in understanding what the Keraring, MyoRing and Ferrara Rings are is understanding its indication: to rehabilitate vision in corneal ectasias (particularly keratoconus). Keratoconus and other related ectasias, such as pellucid marginal degeneration and keratoglobus, are progressive conditions that weaken the cornea, causing it to thin and bulge into an irregular shape. This distortion leads to vision problems, including blurred or distorted vision, increased light sensitivity, and difficulties with night vision. In advanced cases, corneal scarring may further reduce visual acuity, making daily activities challenging. To restore vision, several treatment options exist, ranging from rigid contact lenses to corneal transplants to intracorneal ring segments (ICRS). However, modern corneal implant techniques and femtosecond-assisted procedures provide less invasive and highly effective alternatives for many patients.
1. What Are Intracorneal Ring Segments (ICRS)?
ICRS such as the Keraring, Ferrara Ring, and MyoRing, are small implants inserted into the cornea to reshape it and improve vision. These ring segments are particularly useful for patients with keratoconus or other corneal irregularities, as they help reduce irregular astigmatism (uneven curvature of the cornea) and improve the overall corneal shape.
The key advantage of ICRS is that they offer a less invasive and reversible alternative to corneal transplantation. Instead of replacing the cornea, these implants modify its shape, allowing patients to retain their natural corneal tissue while improving their vision.
ICRS work by acting as spacers within the corneal layers. The cornea is made up of a tough, transparent tissue containing collagen fibers that maintain its structure. When ICRS are inserted into the peripheral corneal stroma (the middle layer of the cornea), they create space and change the cornea’s shape. This process is known as the arc-shortening effect, meaning the cornea becomes less steep in the center. A steeper cornea distorts vision, so flattening it leads to clearer sight.
The amount of flattening achieved depends on two factors:
- Thickness of the implanted segment – Thicker ring segments apply more force to the corneal tissue, resulting in greater flattening.
- Diameter of the implantation site – If the rings are placed closer to the center, the effect is stronger; if placed farther out, the effect is gentler.
In simple terms, these ring segments gently press against the cornea from the inside, reshaping it into a more regular dome shape. This helps reduce the bulging effect seen in keratoconus and improves vision by making the corneal surface more uniform.
2. ICRS: Keraring vs. Ferrara Ring vs. MyoRing – What’s the Difference?
While all three options serve the same general purpose, they differ in their design and application:
- Keraring: Made of polymethylmethacrylate (PMMA), a biocompatible material, Keraring segments are designed with a triangular cross-section and are available in various arc lengths and thicknesses. They are typically used for moderate keratoconus cases to provide controlled corneal flattening and improve vision quality.
- Ferrara Ring: Similar to Keraring, the Ferrara Ring is also made of PMMA and features a triangular cross-section. However, it offers different optical zone diameters and arc lengths, allowing for customization based on the patient’s specific corneal topography. This design is often utilized in more advanced keratoconus cases where a tailored approach is necessary to achieve the desired corneal reshaping.
- MyoRing: Distinct from the segmented designs of Keraring and Ferrara Ring, the MyoRing is a continuous, complete ring implanted into a corneal pocket created within the stroma. This full-ring design provides uniform support to the cornea, making it suitable for severe keratoconus cases where additional corneal stability is required. The implantation of the MyoRing can effectively reduce corneal steepening and improve visual acuity, offering a viable alternative to more invasive procedures.
3. Femto-CAIRS: A New Approach
Femto-CAIRS (Femtosecond Laser-Assisted Corneal Allogenic Intrastromal Ring Segments) represents the latest advancement in corneal implants, offering significant advantages over traditional synthetic ICRS. Instead of using artificial plastic segments, Femto-CAIRS utilizes corneal tissue from a human donor (allogenic tissue). This biologically compatible material integrates naturally with the patient’s eye, reducing the risk of complications such as migration, extrusion, or rejection.
A key differentiator of Femto-CAIRS is the use of a highly precise femtosecond laser, which ensures meticulous placement of the allogenic segments. This advanced technology allows for customization of both depth and positioning, optimizing corneal reshaping and maximizing visual outcomes. Studies have shown that Femto-CAIRS effectively flattens the central cornea, reduces irregular astigmatism, and provides longer-lasting stability compared to synthetic alternatives.
4. Who Can Benefit?
Femto-CAIRS and traditional ICRS procedures are most beneficial for patients with mild to moderate keratoconus who still have a sufficiently thick cornea to support these implants.
Patients who experience significant vision distortion due to corneal ectasia but are not yet at the stage of requiring a corneal transplant are ideal candidates. Those with severe cases, where corneal thickness is too compromised, may still require more advanced surgical interventions, such as deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PKP). Where scarring is involved, phototherapeutic keratectomy (PTK), where an excimer laser is used to remove scar tissue from the cornea, may also be a treatment option.
Conclusion
For individuals suffering from keratoconus and other corneal ectasias, corneal implants like the Keraring, Ferrara Ring, and MyoRing offer valuable treatment options. However, the emergence of Femto-CAIRS has redefined what is possible in vision rehabilitation, providing a superior alternative that combines biological compatibility with cutting-edge femtosecond laser precision.
Consulting an experienced ophthalmologist is crucial in determining the most appropriate treatment for each patient. At the ELZA Institute, specialists in keratoconus and corneal ectasia offer personalized solutions, including the latest innovations in corneal implants and Femto-CAIRS, ensuring the best possible visual outcomes for every patient.
