Eyeworld

EW REFRACTIVE 148 April 2017 by Michelle Stephenson EyeWorld Contributing Writer fornia]). A 6.5-mm optical zone was used with a preset 120-μm ablation depth. A blend zone was not used, and the laser was centered on the pupil. The lights in the room were turned off, and the laser was pulsed while watching the monitor for the blue autofluorescence of the laser striking the corneal epithelium. "We waited until a dark area presented, which indicated the first area of epithelium breaking through. After noting how many microns of epithelium had been removed (as shown by the laser display), we continued ablating until all epithe- lium was removed, as signaled by lack of blue autofluorescence. The final depth of ablation was record- ed, and topical mitomycin C 0.02% was applied for 15 seconds. This was followed by thorough irrigation of the ocular surface with sterile bal- anced saline solution, placement of a bandage contact lens, and admin- istration of a topical nonsteroidal anti-inflammatory drug, steroid, and antibiotic eye drops," she explained. The patient was followed daily until corneal re-epithelialization occurred, at which time the con- tact lens was removed. Antibiotic eye drops were continued through the last day of contact lens wear, and steroid eye drops were slowly tapered over the course of a month. The patient's initial topography, topography 3 months after cross- linking, and topography 3 months post-PTK show an 8 D improvement in corneal astigmatism and a 10.6 D decrease in maximal keratometry. Additionally, the patient's BCVA improved from counting fingers to 20/40 with a rigid gas-permeable contact lens. Surface ablation Many patients who undergo "Shoot- ing the Blue" PTK, even those with significant amounts of astigmatism or irregular astigmatism, are then able to safely undergo other re- fractive procedures, such as PRK. Without this technique, this simply would not be possible. EW Editors' note: Dr. Nattis has no finan- cial interests related to this article. Contact information Nattis: asn516lu@gmail.com The corneal epithelium at the site of the cone can be used as a masking agent "Shooting the blue" PTK for keratoconus Figure 1. The patient's initial topography Figure 2. The patient's topography 3 months after cross- linking Figure 3. The patient's topography 3 months after PTK Source (all): Alanna Nattis, MD D uring phototherapeu- tic keratectomy (PTK), surgeons typically use a masking agent that sits on top of the cornea. This prevents the irregularity from being transmitted downward during the lasering of the cornea. During "Shooting the Blue" PTK for kerato- conus, surgeons use the epithelium as the masking agent. "In these cases, the epithelium fluoresces when you hit it, and it turns blue. Once you get through the epithelium, you can see black. As the laser is firing, you see blue and then a black circle coming through. This way, once we have lasered through all the blue and the black is showing through, we know that we have lasered off all of the epithelium and now we are at a smooth surface. In the future, if we want to do a PRK or a refractive procedure, we know that the surface of the cornea has been smoothed out," said Alanna Nattis, DO, Garden City, New York. She learned this technique from her fellowship mentor, Eric Donnen- feld, MD, who exposed her to new and exciting treatment technologies and techniques for treating kerato- conus and other corneal disease. Case study Dr. Nattis recently performed "Shooting the Blue" PTK on a 21-year-old woman with a history of keratoconus, which was more significant in the left eye than in the right eye. Additionally, she had undergone collagen crosslinking in 2011. Topography showed that she had a significant amount of irregular astigmatism (12 D). Even with rigid gas-permeable contact lenses, her best corrected visual acuity (BCVA) was counting fingers. She was in- terested in improving her vision by laser; however, Dr. Nattis was unable to obtain adequate measurements for topography-guided PRK. The decision was then made to smooth the corneal surface using transepithelial PTK ("shooting the blue" technique). Here, the epithe- lium of the cornea was used as a masking agent, and PTK was per- formed using the VISX STAR S4 laser (formerly Abbott Medical Optics [AMO], now Johnson & Johnson Vision [J&J Vision, Santa Ana, Cali-

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