The other type forms as very thick contractile membranes which pull at the retina. These are opaque and block the light falling on the retina so the retinal reattachment surgery needs to be performed after manually peeling the membrane off. Cytokines involved in PVR
A number of cytokines such as tumor necrosis factor alpha (TNFα), transforming growth factor beta 2 (TGFβ2), platelet derived growth factor (PDGF) and interleukins have been shown to play a role in PVR progression. TGFβ2 levels have been shown to be elevated up to three times normal during the progression of PVR. TGFβ2 is the most predominant isoform in the eye and is secreted as a latent inactive peptide into the vitreous by epithelial cells of the ciliary body and the lens epithelium and is also produced by the RPE cells and the Muller cells of the retina. TGFβ2 is known to induce EMT in RPE cells and fibrosis in the eye. Expression of PDGF in particular PDGF-AA is triggered during ocular injury and contributes to PVR pathology. RPE cells express the receptor for hepatocyte growth factor (HGF). HGF stimulates RPE cell migration and its presence is also strongly detected in retinal membranes. Interleukin 6 levels are elevated in the vitreous humor during PVR. References
External links
GeneReviews/NCBI/NIH/UW entry on VCAN-Related Vitreoretinopathy
The lymph ends its journey in the thoracic duct or right lymphatic duct, which drain into the blood circulation. Diagnosis
Diagnosis is generally based on signs and symptoms, with testing used to rule out other potential causes. An accurate diagnosis and staging may help with management. A swollen limb can result from different conditions that require different treatments. Diagnosis of lymphedema is currently based on history, physical exam, and limb measurements. Imaging studies such as lymphoscintigraphy and indocyanine green lymphography are only required when surgery is being considered. However, the ideal method for lymphedema staging to guide the most appropriate treatment is controversial because of several different proposed protocols. Lymphedema can occur in both the upper and lower extremities, and in some cases, the head and neck. Assessment of the extremities first begins with a visual inspection. Color, presence of hair, visible veins, size and any sores or ulcerations are noted. Lack of hair may indicate an arterial circulation problem. Given swelling, the extremities circumference is measured for reference as time continues. In early stages of lymphedema, elevating the limb may reduce or eliminate the swelling. Palpation of the wrist or ankle can determine the degree of swelling; assessment includes a check of the pulses. The axillary or inguinal nodes may be enlarged due to the swelling. Enlargement of the nodes lasting more than three weeks may indicate infection or other illnesses such as sequela from breast cancer surgery requiring further medical attention.Diagnosis or early detection of lymphedema is difficult.