How reliable is oct scan in diagnosing glaucoma?

Maybe: The diagnosis of glaucoma relies on many pieces of data. The shape of the optic nerve, retinal nerve fiber layer thickness, visual field testing, c:d volume and rim thickness, intraocular pressure and changes in these parameters over time. It is rare for only one to be abnormal i would suggest a second opinion before starting treatment. Don't just ignore the possible DX , glaucoma can blind.

Can be: Depends on severity of disease, and if there are any other causes that can thin the retinal nerve fiber layer. Also, usually best to correlate it with classical functional loss (progressive). A diagnostic tool but can be faulty when used alone.