EyeWorld India March 2016 Issue

55 EWAP DEVICES March 2016 by Michelle Dalton EyeWorld Contributing Writer Treating keratoconus continued on page 56 Corneal crosslinking and intracorneal ring segments for higher levels of keratoconus T reating keratoconus in the U.S. will likely involve contact lenses, followed by intracorneal ring segments (ICRS) and/or corneal transplant with either penetrating keratoplasty or deep anterior lamellar keratoplasty if vision correction is not possible with noninvasive means. Outside the U.S., however, surgeons are also able to combine these procedures with corneal crosslinking (CXL). At press time there were no commercially approved CXL devices in the U.S. Mitchell A. Jackson, MD , founder and CEO, JacksonEye, Lake Villa, Ill., has tapered the use of Intacs (Addition Technology, Lombard, Ill.) “because contact lens fitting has become much more advanced. Most patients who received Intacs for keratoconus were going to need contact lenses anyhow; if you catch keratoconus early enough you can perform CXL, which has better outcomes than Intacs in terms of truly halting the progression of the disease. Some surgeons are combining the procedures, which is what I’ll likely do once CXL is approved in the U.S.” If the patient is young enough, he might even consider the Visian ICL (STAAR Surgical, Monrovia, Calif.), for reduction of the high myopic component typically seen, but only if the cornea and refraction are stable; he will not consider a toric ICL once FDA approved due to difficulty in knowing the correct axis to place the ICL in these patients. Intacs will have an excellent place in conjunction with CXL for lower myopic correction when needed, he said. Even though intracorneal ring segments can create biomechanical changes on the cornea, “they do not have an effect on disease progression, therefore, if progression is suspected, a CXL procedure needs to be performed in combination with the use of these devices,” said Mauricio Perez, MD , Salvador Hospital/Clinica Las Condes, Santiago, Chile. “Our protocol with ICRS is to perform a same-day CXL in order to try to lock the biomechanical and flattening effect of the ICRS and at the same time, attempt to stop progression of the disease. The only cases in which we do not perform same-day CXL while using ICRS are in previously crosslinked corneas.” Aylin Kilic, MD , consultant, Dunya Eye Hospital, Istanbul, Turkey, has “extensive experience” with ICRS but has not seen the same improvement after implantation as reported in the literature. She will, however, implant Intacs in higher levels of keratoconus, “or I’ll combine CXL and Intacs.” Although keratoconus has recognized stages, these are mostly reliant upon “keratometric values and pachymetry, but those two parameters are not always parallel with one another,” Dr. Kilic said, and with the use of more sophisticated topography, she does not always abide by the staging to determine treatment. “Patient selection is still very important,” she said. “If you perform ICRS on someone with very good visual acuity, they may end up with an irregular astigmatism and visual loss. But if there is progression and high refraction, performing CXL and ICRS together is helpful. ICRS is also a kind of refractive surgery.” Using ICRS can help improve corneal shape, and most patients will achieve some visual improvement, but they are not risk-free, said William Trattler, MD , Center for Eye Care Excellence, Miami. “Some studies have reported up to 10% of enrolled eyes needing removal of the Intacs segment.” Intacs, Intacs SK, CXL, and others When using ICRS, the decision between using single or double segments can depend on several factors, Dr. Perez said, including recommendations from a particular device company, personal surgeon preferences, or a particular nomogram. Some studies, particularly Sharma and Yeung, 1,2 describe better uncorrected and corrected vision, greater cylinder decrease and infero-superior ratio improvement with single segments, he said. “In my early experience with ICRS, I used to choose either single or double segments based on company-based nomograms for a particular device, but I have leaned toward single-ICRS use, with good results, in order to theoretically only induce corneal flattening in the location of greatest steepness, which usually is located inferotemporally, for most cones, and not flatten the superior cornea, which could potentially lead to further distortion,” he said. Intacs SK is a newer design that has an inner diameter of 6 mm, oval cross section, and two different thicknesses (0.40 and 0.45 mm), designed for those with more severe keratoconus. “In theory, the smaller the inner diameter of the device, the greater the flattening effect should be, and based on that logic, the Intacs SK, positioned in the location of the cone, has become my go-to single device when considering an ICRS,” Dr. Perez said. The primary reason to continue implanting ICRS, Dr. Jackson said, is to flatten the cornea enough and reduce the myopia enough to enable contact lens fitting. “CXL will be my first line of treatment because the ultimate goal is to prevent disease progression,” he said. “Implanting Intacs with CXL will not only stop the disease but make the lens fit easier. When it’s available, I’ll do both epi-on CXL and Intacs simultaneously so patients only have to go through one procedure.” Dr. Perez also agreed the main goal of ICRS is “to improve uncorrected visual acuity and contact lens tolerance. On the other hand, the main goal with CXL is to alter disease progression by strengthening the cornea” so he thinks these are two synergistic— but not interchangeable— procedures.