Normal healthy eyes have RNFL thickness of how many microns or greater?

• A. 75 microns
• B. 80 microns
• C. 85 microns
• D. 90 microns

Answer: (B)

RNFL thickness around the optic nerve reflects the amount of retinal nerve fiber tissue present; in healthy eyes, this layer is maintained above a practical lower limit used in OCT interpretation. Clinically, a global peripapillary RNFL thickness of about 80 microns or greater is considered within normal range. Values at or below this threshold raise concern for potential RNFL loss, such as from glaucoma, while true thickness varies by sector (superior and inferior tend to be thicker; nasal and temporal regions thinner) and by instrument-specific normative databases. Therefore, 80 microns is the threshold used to distinguish normal from thinner, possibly abnormal RNFL in many practice settings.