Glaucoma exam dr. noted there was a questionable change to rnfl but didn't seem concerned. said tests looked good & glaucoma stable. what is rnfl?

Nerve fibers: The optic nerve is a cable with a million fibers. This is a measurable thickness. In glaucoma, there is a loss of fibers and thus, lower measurements or thinning. The RNFL thickness is measured and tracked overtime, with lower numbers suggesting thinning and progression of glaucoma. Its not a perfect test with a margin of error, sometimes only offering 'questionable' changes.