Subretinal fluid ferning test in rhegmatogenous retinal detachment

PURPOSE. The ferning test involves a process of crystallization achieved si mply by removing water and is feasible for all ocular fluids. The ferning t est of subretinal fluid (SRF) from patients with rhegmatogenous retinal det achment (RRD) reveals three different patterns: type 1 showing thin crystal s, type 2 with larger crystals and type 3 with small, curvilinear structure s with no tree-like appearance. The present study was designed to determine whether the SRF ferning test is correlated with the clinical features and the surgical outcome of RRD. METHODS. A series of 65 consecutive patients with RRD at the first onset we re considered. Particular attention was paid to duration, extension, and su rgical outcome of RRD. SRF samples were collected during scleral buckling s urgery. The fluid was dropped onto the slide of a light microscope, left to dry, and examined under the microscope. RESULTS. There was a significant difference between SRF ferning types I and 2 as regards duration and extension (both p < 0.001). There was also a sig nificant difference between SRF ferning types 2 and 3 as regards duration ( p < 0.001), extension (p < 0.001), and surgical outcome (p < 0.05). CONCLUSIONS. The ferning test of SRF is quick and simple and can be regarde d as a useful tool for obtaining information about clinical features, such as duration or extension of first onset in uncomplicated cases of RRD espec ially for purposes of forensic medicine.