Drugs that interfere with vitamin A processing in the retina or pigment epithelium can induce ocular damage. In an in vitro system, it is demonstrated that retinoic acids, which are used to treat skin problems and induce night blindness, block the ocular retinol dehydrogenases. This results in increased levels of retinol in the eye. However, more research needs to be done on this topic before a conclusion can be made about whether or not vitamin A can cause blindness.