EyeWorld Asia-Pacific June 2011 Issue

24 June 2011 EW REFRACTIVE Views from Asia-Pacific Li Xiaoxin, MD Chair, People’s Eye Center & Eye Institute, People’s Hospital of Peking University 11 Xizhimen South Street, Beijing 100044, China Tel. no. 88326666 Fax no. 68318386 drxiaoxinli@gmail.com I don’t agree that myopic CNV is a complication of LASIK, because: 1. The retinal complications of LASIK are usually retina interface lesions like macular hole or vitreo–retina traction syndrome caused by posterior vitreous detachment that may be induced by very high pressure during the creation of the flap; this complication happens very rarely. 2. Myopic CNV can happen at any time with myopia, and is a lesion originating in the choroid; some authors (Ohno-Matsui K, 2003; Hayashi K, 2010) have reported the lacquer cracks as predictive factors for developing CNV in high myopia. Lacquer cracks in the macular area can occur with normal visual acuities, and may not seem remarkable during routine ocular fundus examination if we are not paying special attention. 3. If any laser ablation waves travel through the vitreous and hit the retina, we may find some changes in large areas of the retinal, such as a “window defect” in fluorescein angiography. The window effect means some breakage of the RPE that might induce CNV; in this case, there was no breakage. Editors’ note: Prof. Li has no financial interests related to his comments. Although choroidal neovascularization is traditionally linked to AMD (pictured here), a study examined a case that appeared in a healthy woman after LASIK Source: Kang Zhang, MD, PhD Healthy patient develops rare complication T he LASIK surgery appeared to go off without a hitch in a young, healthy moderate myope. Weeks later, however, practitioners found that they were dealing with choroidal neovascularization, according to Sherry J. Bass, OD, distinguished teaching professor, SUNY State College of Optometry, New York, NY, USA. Investigators recently reported on the case and related literature review in the 20 August 2010 e-issue of Optometry . While choroidal neovascularization is commonly linked to age-related macular degeneration, as well as some inflammatory conditions like ocular histoplasmosis and acquired maculopathies, there has been almost no connection to LASIK previously reported. “If you look at the literature, the incidence of this happening after LASIK is extremely rare,” Dr. Bass said. “Of 30,000 patients, one was reported to have this develop after LASIK [without predisposing factors].” It was with this in mind that investigators decided to publish the case. “The reason that we reported it was because this was a patient who had no predisposing abnormality in the macula,” Dr. Bass said. “She was a routine myope [–5 D], not a very high myope, and developed this 6 weeks after LASIK.” Occurring out of the blue The patient’s pre-exam was uneventful, she had no history of any problems, and the LASIK itself went off without any complications. Then after 6 weeks, she presented with distortion in her left eye. “We looked at her retina and she had fluid in her macula,” Dr. Bass said. “First we did an OCT [optical coherence tomography] and then a fluorescein angiography, and the OCT demonstrated that a possible neovascular net had developed.” Fluorescein confirmed that she had a classic choroidal neovascular net beneath her macula. Practitioners referred the patient to a retinal specialist who treated her with photodynamic therapy and triamcinolone. She ultimately did very well. “Her visual acuity at the time that she developed this net was 20/50 [6/15], and over the course of 3 months she improved to 20/20 [6/6],” Dr. Bass said. “She had no long-lasting effects.” Investigators were able to find just one other case in the literature in which a LASIK patient with no predisposing factors developed this condition. “This patient had a hyperopic refractive error and didn’t have any retinal abnormalities,” Dr. Bass said. There are two theories on what may lead to neovascularization post-LASIK in otherwise normal eyes. “The main theory is that during the course of LASIK when the surgeon applies the On the lookout for choroidal neovascularization after LASIK by Maxine Lipner Senior EyeWorld Contributing Editor microkeratome to create the flap, the eye is exposed to very high pressure,” Dr. Bass said. “Most eyes can tolerate that pressure without a problem, but if there is an eye that has some kind of congenital weakness in Bruch’s membrane, that high pressure, even for a very short period of time, can possibly cause a break in Bruch’s membrane.” A second theory centers on the photoablation process itself. “The other possibility is that the photoablation with the laser can create these waves that travel through the vitreous and hit the retina,” Dr. Bass said. “In a normal eye it doesn’t cause any damage— it’s a very mild force—but maybe in an eye that has some type of a weakness it’s enough of a force that it could cause a break in Bruch’s membrane.” continued on page 27