Eyeworld

EW REFRACTIVE SURGERY 110 September 2015 by Matt Young and Gloria D. Gamat EyeWorld Contributing Writers PiXL, KAMRA, and—for extreme refractive error— the Visian ICL O phthalmologists will for- ever push the envelope to achieve a smaller surgical footprint. That's why LASIK isn't the endgame of refractive surgery, but rather the beginning of the beginning. As far as minimally invasive refractive surgery goes, this is especially true. Advancements in technology and refractive surgical techniques have brought about a wide range of refractive correction procedures that are even more minimally invasive. Here we look at two of the latest advancements and a third (the Visian ICL, STAAR Surgical, Monrovia, Calif.) that is standing the test of time to provide a mini- mally invasive LASIK alternative for extreme refractive error. Non-invasive, topography- guided crosslinking In corneal refractive surgery, refrac- What's more minimally invasive than LASIK? Patient undergoing accelerated crosslinking with the KXL II system Source: Peter Hersh, MD Patient undergoing vision correction surgery with the KAMRA inlay Source: Jeffery J. Machat, MD tive errors are corrected through techniques that reshape the cornea either by surgery or by laser treat- ment. When corneal crosslinking with riboflavin and ultraviolet-A (UVA) was introduced, it provided an option that reshapes the cor- nea by changing its biomechanical structure. The standard technique was designed to stabilize the pro- gression of ectatic corneal disorders such as keratoconus and corneal ectasia. However, basic science and clinical research have expanded the potential utilities of crosslinking. Today, accelerated crosslinking using higher power UV sources can reduce procedure time from 30 minutes to 3 minutes or less. In addition, Photorefractive Intrastromal Cross- linking (PiXL) using the KXL II System (Avedro, Waltham, Mass.) can address topography irregularities and refractive errors as well. "PiXL is a topography-guided crosslinking," said Peter Hersh, MD, Cornea & Laser Eye Institute – Hersh Vision Group, Teaneck, N.J. "The KXL II System incorporates eye tracking to properly pattern and apply the UVA energy needed." "PiXL has two goals," Dr. Hersh said. "In irregular corneas, such as in keratoconus, we can use topography both to guide the power and the pat- tern of the UV light on the cornea to obtain crosslinking individualized to the patient's corneal irregularity, and for refractive surgery, we are able to pattern the energy in order to correct lower degrees of nearsight- edness, farsightedness, and astigma- tism." PiXL is extremely non-invasive, according to Dr. Hersh. "Unlike LASIK or PRK, which are removing tissue, [PiXL] doesn't vi- olate the tissue per se, but it chang- es the shape of the cornea on a biomechanical basis," he said. "It is a new kind of platform where we are changing the corneal biomechanics and corneal microarchitecture in order to correct refractive error." While LASIK is most suitable for higher degrees of myopia, PiXL best suits patients with lower degrees of refractive error. "It is a standalone procedure for lower degrees of hyperopia, myopia, or astigmatism," Dr. Hersh explained. "But we also see that it might have a good place as an en- hancement procedure in post-cata- ract surgery, where there is a residual refractive error that can be corrected in a non-invasive way." PiXL provides ophthalmic surgeons with an enhancement tool that can proceed without much in- tervention. However, experts are still defining the limits. Corneal inlays over multifocal ablation In the last 10 years, several gener- ations of corneal inlays have been developed and refined. Made of an inert material called polyvinylidene fluoride (PVDF), the KAMRA corneal inlay (AcuFocus, Irvine, Calif.) is a disc-shaped inlay that is 6 microns thick, 3.8 mm in diameter and has a 1.6 mm opening. "The KAMRA corneal inlay has 8,400 tiny perforations throughout the inlay in a pseudo randomized pattern," said Jeffery J. Machat, MD, chief medical director, Crystal Clear Vision, Toronto. "Weighing only as much as a crystal of salt, it is an incredibly refined type of inlay that works on extending the range

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