Rating Feedback for Dr. Hoenig (5309893)

The rating:
'I was looking into getting eyelid surgery and wanted to find real patients of this Doctor. I see that he's getting great reviews here. However, I met up with 2 woman who were former patients. One had her eyelids done and had these big Scars coming from the outer corners of each eye. She told me she has a lot of eye problem now and regrets going to him. The other had 5fu injected in her face. She told me that the 5fu gave her indents and thinned out her skin area. She also regrets going to him. I had an appointment set up already but after hearing from them I decided against it and canceled.'
(http://www.ratemds.com/doctor-ratings/100186)
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What is 5Fu injections?