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Perfluorocarbon liquid manipulation of high-density intraocular foreign bodies
1W.K. Kellogg Eye Center, Department of Ophthalmology, University of Michigan School of Medicine, Ann Arbor 48105, USA.
Background:
Perfluorocarbon liquids (PFCLs) are useful for floating various materials off the posterior retina during vitreoretinal surgery. It is generally assumed that buoyancy forces restrict this use to objects with specific gravity lower than that of PFCLs.
Methods:
We tested potential intraocular foreign body materials with specific gravities ranging from 1.1-8.7. The relative affinities of each material for saline and PFCL (specific gravity 1.94) were determined. For each material, we then tested the ability of several specimens of increasing surface/volume ratio to float at the saline-PFCL interface in a glass beaker.
Results:
All materials with specific gravity higher than PFCL demonstrated a greater affinity for saline than for PFCL. Specimens of each of these dense materials floated at the saline-PFCL interface, provided that the surface/volume ratio of the specimen was above a critical value. The critical surface/volume ratio for each material was directly proportional to its specific gravity.
Conclusions:
PFCLs may be useful for manipulating a variety of intraocular foreign bodies, even those with specific gravities higher than PFCL. Surface forces, in addition to buoyancy, govern the disposition of small foreign bodies at the saline-PFCL interface.