Possible reason for CD ratio varying

[melinda68]

Hello doctor. My glaucoma specialist says my CD ratios are .2 and .4. The OCT puts them them both at .7. When I asked her why the difference, she brushed me off and said her measurement was correct. What could account for the difference, since it is substantial?

[JohnHaganMD]

Cup/Disk measurements made my Eye MDs or non-MD optometrists are wildly subjective. This has been proven many times.  Even an MD making measurements on the same patient and the same day if the patient is masked given different results.  So it is at best an estimate.  The OCT is much more accurate however it also is subject to error largely based on the 'signal strength" which should be 9 or 10. If lower it also can have errors.  With glaucoma its the sum total of all the data: IOP,  NFL OCT,  visual C/D, visual field, corneal thickness, age, refractive error, family history.

[melinda68]

The signal strength was good. 10/10 OD and 8/10 OS. I just don't understand why she is adamant that my CD ratio is good (if asymmetric) when the OCT tell me it's awful (but symmetric). I know this a question best for her ,but she won't answer anything but "what I say goes"

[JohnHaganMD]

Doctor knows best went out the door 50 years ago in the USA.  You don't have to live with it. Lots of other communicative Eye MDs most places.