Intacs Corneal Implants for Keratoconus
What Are Intacs Corneal Implants
Intacs corneal implants are small, arc-shaped devices placed within the cornea to reshape its surface and improve vision in patients with keratoconus. According to a 2024 study in the American Journal of Ophthalmology using CDC data, the national prevalence of keratoconus in the U.S. was 0.04% in 2019, with an estimated 132,089 diagnosed Americans, and a cumulative economic burden of $3.8 billion. As keratoconus causes the cornea to thin and bulge into an irregular cone shape, glasses and standard contact lenses may no longer provide adequate correction. This outpatient procedure offers a tissue-sparing alternative for patients who are not yet candidates for corneal transplantation.
Intacs are a type of intrastromal corneal ring segment (ICRS), a category of tiny implants designed to flatten and stabilize the corneal surface from within. Each Intacs segment is a crescent-shaped insert made of polymethyl methacrylate (PMMA), the same biocompatible polymer used in intraocular lenses for cataract surgery. The material has a long safety record in eye surgery and is well tolerated by corneal tissue. Intacs are available in different thicknesses, and cornea specialists select the appropriate size based on the degree of corneal steepening present in each eye.
While specialty contact lenses sit on the surface of the eye and must be inserted and removed daily, Intacs are surgically placed inside the corneal stroma, the middle structural layer of the cornea. Once implanted, they remain in position without any daily maintenance. This distinction makes Intacs particularly valuable for patients who struggle with contact lens comfort or cannot achieve adequate vision through lens wear alone.
Intacs were originally approved to treat mild nearsightedness and later received FDA approval specifically for keratoconus. The implants work by supporting and reshaping the weakened corneal tissue, reducing the irregular astigmatism that distorts vision in keratoconus patients. It is important to understand that Intacs reshape the cornea but do not halt the underlying progression of the disease.
How Intacs Help Keratoconus Patients
The primary goal of Intacs is to improve the optical surface of the cornea so that light focuses more accurately on the retina. When placed in the peripheral cornea, Intacs push outward against the surrounding tissue and flatten the steep central cone caused by keratoconus. A thicker ring segment produces a greater flattening effect. This mechanical reshaping reduces the asymmetric curvature that makes clear vision so difficult for keratoconus patients.
Many patients experience measurable improvement in both uncorrected and best-corrected visual acuity after Intacs placement. Published studies have shown reductions in mean keratometry values of over 3 diopters at five-year follow-up, with the greatest visual gains typically seen in patients with more advanced corneal irregularity. Results vary by individual, and some patients may still benefit from glasses or contact lenses after the procedure for fine visual correction.
For patients who have developed intolerance to rigid gas permeable lenses or scleral lenses, Intacs can restore enough corneal regularity to make lens fitting easier or, in some cases, reduce the need for specialty lenses altogether. By improving the underlying corneal shape, Intacs may also allow patients to transition to simpler lens designs. Cornea specialists work closely with specialty contact lens fitters to coordinate post-implant lens optimization when needed.
Who Is a Candidate for Intacs
Not every keratoconus patient is a suitable candidate for Intacs. A thorough evaluation helps determine whether the procedure is likely to provide meaningful benefit. The best candidates for Intacs typically have mild to moderate keratoconus with a maximum keratometry (Kmax) value below 55 to 58 diopters. A minimum corneal thickness of 400 micrometers at the planned implantation site is required to safely create the channel for the ring segments. The central cornea should be clear, without significant scarring or opacities that would limit visual improvement.
Cornea specialists generally consider Intacs when a patient can no longer achieve adequate vision with glasses or contact lenses and is not yet a candidate for corneal transplant surgery. Patients who experience contact lens intolerance, whether from discomfort, poor fit on an irregular cornea, or inability to wear lenses for extended periods, often benefit the most.
Intacs are generally not recommended for patients whose Kmax exceeds 70 diopters, as the degree of corneal distortion may be too advanced for ring segments to provide adequate correction. Other contraindications include severe corneal thinning at the intended tunnel site, central stromal scarring that would block the visual axis, a history of corneal hydrops (acute fluid buildup in the cornea), and active eye infection or uncontrolled inflammation. Patients with progressive keratoconus may benefit from combining Intacs with corneal cross-linking to address both the shape and structural integrity of the cornea.
How the Intacs Procedure Is Performed
The Intacs implantation is an outpatient procedure that typically takes about 15 to 20 minutes per eye. Before surgery, cornea specialists perform a comprehensive eye examination that includes corneal topography, pachymetry (corneal thickness measurement), and a detailed slit-lamp evaluation. These measurements guide the selection of ring segment thickness and placement position. Patients receive specific instructions about medications and activity restrictions in the days leading up to the procedure.
The eye is numbed with topical anesthetic drops, and a small incision is made in the peripheral cornea. The surgeon then creates a curved channel, or tunnel, between the layers of the corneal stroma, outside the central optical zone where you see through. One or two crescent-shaped Intacs segments are carefully inserted into this channel. The incision is then closed, and a protective contact lens may be placed on the eye temporarily.
Many surgeons now use a femtosecond laser to create the corneal channel rather than a manual dissection tool. This laser-assisted technique allows for more precise tunnel dimensions, more consistent implant depth, and improved symmetry. Studies have demonstrated that femtosecond laser-assisted placement reduces the risk of intraoperative complications such as shallow or uneven channels.
Frequently Asked Questions
Yes, combining Intacs with corneal cross-linking is a well-established treatment strategy. Intacs reshape the cornea to improve vision, while cross-linking strengthens the corneal collagen to slow or halt disease progression. The two procedures may be performed during the same session or staged separately depending on clinical circumstances. This combined approach addresses both the structural weakness and the optical distortion caused by keratoconus.
Many patients notice improved vision within the first few days to weeks after surgery. The degree of improvement depends on factors such as the severity of keratoconus, cone location, and corneal thickness. While some patients achieve functional vision without correction, others still benefit from glasses or contact lenses after the procedure. Intacs are not designed to eliminate refractive error entirely but rather to bring the cornea closer to a shape that can be effectively corrected.
Intacs are designed to remain in the cornea long term, but one of their key advantages is reversibility. If a patient's vision needs change, or if the implants do not provide the expected benefit, cornea specialists can remove or exchange the segments. Once removed, the cornea gradually returns toward its pre-implant shape, preserving future treatment options including corneal transplantation if needed.
Most patients can return to light daily activities within one to two days after the procedure. Vision may fluctuate during the first several weeks as the cornea adjusts to the implants. Prescription eye drops, including antibiotics and anti-inflammatory medications, are typically used for several weeks following surgery. Full visual stabilization generally occurs within one to three months, and follow-up appointments allow the team to monitor healing and adjust any lens prescriptions as needed.
Intacs carry one of the most favorable safety profiles among intrastromal corneal ring segments. Potential risks include infection, glare or halos around lights, segment migration or extrusion, and under-correction or over-correction of the corneal shape. In rare cases, the channel creation may be incomplete, requiring the procedure to be paused or revised. Serious complications are uncommon, and the reversibility of the implants provides an added layer of safety.
Intacs are one of several keratoconus treatment options available depending on disease severity. In early keratoconus, specialty contact lenses and cross-linking may be sufficient. Intacs fill an important role for patients with moderate disease who need more corneal reshaping than lenses alone can provide but do not yet require a transplant. Understanding the full spectrum of available treatments helps guide informed decisions at each stage of the condition.
What our Patients say
4.8
Reviews
(3547)