Hyaluronan is naturally found in many tissues of the body, such as skin, cartilage, and the vitreous humour. It is therefore well suited to biomedical applications targeting these tissues. The first hyaluronan biomedical product, Healon, was developed in the 1970s and 1980s by Pharmacia, and is approved for use in eye surgery (i.e., corneal transplantation, cataract surgery, glaucoma surgery and surgery to repair retinal detachment). Other biomedical companies also produce brands of hyaluronan for ophthalmic surgery. Hyaluronan is also used to treat osteoarthritis of the knee. Such treatments, called viscosupplementation, are administered as a course of injections into the knee joint and are believed to supplement the viscosity of the joint fluid, thereby lubricating the joint, cushioning the joint, and producing an analgesic effect. It has also been suggested that hyaluronan has positive biochemical effects on cartilage cells. However, some placebo controlled studies have cast doubt on the efficacy of hyaluronan injections, and hyaluronan is recommended primarily as a last alternative to surgery. Oral use of hyaluronan has been lately suggested, although its effectiveness needs to be demonstrated. At present, there are some preliminary clinical studies that suggest that oral administration of Hyaluronan has a positive effect on osteoarthritis, but it remains to be seen if there is any real benefit to the treatment. Dry, scaly skin (xerosis) such as that caused by atopic dermatitis (eczema) may be treated with a prescription skin lotion containing sodium hyaluronate as its active ingredient. Due to its high biocompatibility and its common presence in the extracellular matrix of tissues, hyaluronan is gaining popularity as a biomaterial scaffold in tissue engineering research. In particular, a number of research groups have found that hyaluronan's properties for tissue engineering and Regenerative medicine are significantly improved with crosslinking, producing a hydrogel. This added feature allows a researcher to form a desired shape as well as to deliver therapeutic molecules into a host. In some cancers, hyaluronan levels correlate well with malignancy and poor prognosis. Hyaluronan is thus often used as a tumor marker for prostate and breast cancer. It may also be used to monitor the progression of the disease. Hyaluronan may also be used postoperatively to induce tissue healing, notably after cataract surgery. Current models of wound healing propose that larger polymers of hyaluronic acid appear in the early stages of healing to physically make room for white blood cells, which mediate the immune response. Hyaluronan has also been used in the synthesis of biological scaffolds for wound healing applications. These scaffolds typically have proteins such as fibronectin attached to the hyaluronan to facilitate cell migration into the wound. This is particularly important for individuals with diabetes who suffer from chronic wounds.