Subretinal fluid ferning test in rhegmatogenous retinal detachment

PURPOSE: The ferning test involves a process of crystallization achieved simply by removing water and is feasible for all ocular fluids. The ferning test of subretinal fluid (SRF) from patients with rhegmatogenous retinal detachment (RRD) reveals three different patterns: type 1 showing thin crystals, type 2 with larger crystals and type 3 with small, curvilinear structures 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 were considered. Particular attention was paid to duration, extension, and surgical outcome of RRD. SRF samples were collected during scleral buckling surgery. 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 1 and 2 as regards, duration and extension (both p < 0.001). There was also a significant 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 regarded as a useful tool for obtaining information about clinical features, such as duration or extension of first, onset in uncomplicated cases of RRD especially for purposes of forensic medicine.