American Academy of Optometry
American Academy of Optometry
October 29, 2019
1 min read

Study results suggest performing OCTs at same time of day

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

Laura P. Pardon

ORLANDO, Fla. – Researchers determined that minimum rim width measures on OCT can vary significantly from one 12-hour period to the next, so the test should be conducted at the same time of day to optimize repeatability, they said

Laura P. Pardon, OD, MS, FAAO, an American Academy of Optometry Ezell Fellow, shared these study results during an academy-sponsored press conference here at the AAO meeting.

“It’s important to understand changes in the optic nerve head throughout the day,” she said at the press conference, so she and her colleagues sought, “to determine repeatability for optic nerve OCT parameters within a given scan session at the same time of day and over a 12-hour daytime period.”

Pardon said she and her colleagues evaluated 10 healthy subjects with a mean age of 29.5 years. OCT scans were performed at 7 a.m., 7 p.m. and another randomly selected time on the same day.

“We quantified the OCT parameters of Bruch’s membrane opening height (the measurement of the anterior and posterior position of Bruch’s membrane) and minimum rim width (the measurement of the neuroretinal thickness) with radial scans,” Pardon said. “We are interested in seeing repeatability of this parameter throughout the day.”

The researchers also used circular scans to calculate global retinal nerve fiber layer and choroid thicknesses.

“We found a considerable decrease in minimum rim width (MRW) throughout the day – 11 microns,” Pardon said. “We did not see changes in the other parameters. Inter-session repeatability for MRW was good, but when we looked at 7 a.m. vs. 7 p.m., the mean difference was -12.2 microns and greater standard deviation.”

MRW is known to be a sensitive measure for detecting optic nerve pathology, Pardon said, but the reasons for its thinning throughout the day and also its association with glaucoma pathophysiology are unknown.

“The reduced intra-session MRW variability suggests that for disease monitoring, OCT scans should be obtained at approximately the same time of day when possible,” she concluded. – by Nancy Hemphill, ELS, FAAO


Pardon LP, et al. Intra-day repeatability of optic nerve optical coherence tomography parameters. Presented at: American Academy of Optometry meeting; Orlando, Fla.; October 22-27, 2019.

Disclosure: Pardon reports no relevant financial disclosures.