When considering the use of antisense technology for in vivo apphcatron, whether for therapeutic development or for the creation of animal models for human diseases, a major problem is that most extracellular compartments are constantly mixing with the blood, lymph, cerebrospinal fluid (CSF), and so forth, and thus constantly diluting the oligonucleotide. A possibly unique exception to this problem is the vitreous, a gelatinous fluid overlying the inner retinal surface. The vitreous is formed early in development and is in essence a relatively closed compartment with no active transport of fluids or ions. Forensic pathologists make use of this fact in determining the composition of electrolytes at the time of death by sampling the vitreal compartment.