How to determine variable usages?

I have written a plugin called Identifier Highlighter that mimics what the built-in "Highlight Usages in File" feature does, but without having to hit CtrlShiftF7 all of the time. It performs the search upon text cursor movement. However, the way I am searching is using the PsiFile tree which just gives me back a dumb textual search. If there is more than one variable called count, for example, I would like to only search the particular instance of count that my text cursor is on, not all instances of the word count in the file. Here is how I am searching the file, can anyone tell me how to determine how to limit my results to just the instance of variable my text cursor is on?

//Get PsiFile parse tree
PsiFile pFile = PsiDocumentManager.getInstance(_editor.getProject()).getPsiFile(_editor.getDocument());
//Get element text cursor is over
PsiElement pElem = pFile.findElementAt(_editor.getCaretModel().getOffset());
PsiSearchHelper search = pElem.getManager().getSearchHelper();
LocalSearchScope localFileScope = new LocalSearchScope(pFile);
//Find all other instances of that element in the file
_elems = search.findIdentifiers(pElem.getText(),localFileScope, UsageSearchContext.ANY);