Guidelines in the Successful Treatment of Keratoconus with Intacs Intrastromal Rings

Keratoconus patients now have exciting treatment options available to halt disease progression as well as to improve corneal morphology and visual function. Corneal Collagen Crosslinking has an established international track record of halting the progression of the disease and the well-planned implantation of Intacs intrastromal rings can significantly improve visually disabling distortion in corneal morphology.


I first started implanting Intacs in my Keratoconus patients in 2008 using the classic manual technique. These cases were famously inaccurate in terms of channel depth and appropriate ring placement. Further, as it was in the early days of Laser Vision Correction, we did not appreciate the limits of the technology in the selection of appropriate cases. As a result, many patients did not achieve the full potential benefit of a surgical procedure that fell into general disrepute in the community of corneal surgeons. With the advent of femtosecond laser technology in the creation of precise channels at 75% depth and an educated approach into candidate selection and surgical planning I began to achieve very satisfying outcomes. Let me take this opportunity to share what I have learned.


The major keys to successful outcomes in INTACS surgery in Keratoconus boil down to appropriate patient selection and the careful delineation of cone morphology. In addition to taking note of Pentacam corneal power and elevation maps, I now make it a practice to look at the cornea with a direct ophthalmoscope against the patient’s red reflex. This step immediately allows me to discern the shape of the pathology (round or oval) as well as if it is central to the axis of vision or displaced downward or eccentric. Central pathology will require symmetric two ring surgical placement while displaced or eccentric cases are best treated with asymmetric ring placement either using a thinner ring above and thicker below or as I have found most effective, a single ring alone below the pathology. I use the 0.45 standard rings exclusively. The entrance incision needs to be placed on the steep corneal meridian. Don’t be afraid of using your keratometer to help check determine this axis as sometimes the Pentacam can get fooled by extremes in corneal shape. In general, patients with mean K readings over 60 diopters associated with significant scarring are poor candidates unless their pathology is sagging and eccentric, in which case a single 0.45 ring can often provide good results.


There is no question that the SK modified rings, not yet available in the US, will create even better outcomes for patients in the future as they sit at a reduce radius and hence closer to the visual axis. Another item on my surgical wish list for 2015.

Dr. Fox

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