. 2022 Oct 6;8:42. doi: 10.1038/s41526-022-00228-1

Table 2.

Findings and limitations of current literature and proposed solutions.

Findings	Limitations	Recommendations
MRI images were obtained before and after flight^1,13–16 with US images mostly obtained inflight^15,17	It may be difficult to compare US and MRI ONSD measurements that are not obtained at the same time.	Consider obtaining images with both MRI and US at baseline to verify consistency across modalities.
Using a curvilinear ultrasound probe²²	It is difficult to compare results between studies if researchers are using different probe types and settings. Linear probes are preferred for ONSD measurements^24,25.	Linear ultrasound probe with appropriate ocular settings should be used for ONSD measurement.
No sample image of measurement method provided^19,21	Difficult to evaluate ONSD measurement quality without a sample image.	Given the large heterogeneity in ONSD measurements^5,8,40, it is important to provide a sample image for qualitative assessment.
No annotation of measurements on sample images^{1,13,14,16–18,20,23}	Difficult to evaluate ONSD measurement depth and structures included without annotation on a sample image.	Sample images should include annotation of depth used and structures included in the measurement.
Unclear measurement depth^{1,13,14,19,21} or non-standard depth²³ recorded	ONSD is measurement can change at different depths.	The measurement should be performed 3 mm from the ONH at the vitreoretinal interface. This should be clearly documented and annotated on the sample published image.
Sample image lacks anatomic differentiation (contrast) needed to accurately measure ONSD¹⁸	Risk for under or overestimation of ONSD.	Image acquisition should provide clear anatomic differentiation of the ONS.
Inclusion of the dura in ONSD measurement²³	Overestimation of ONSD.	ONSD measurement should start at the interface between the Subarachnoid space (hyperechoic on US and hyperintense on T2 MRI) and the dura (Hypoechoic on US and Hypointense on T2 MRI).
Studies combined left and right eye measurements^17,18,20,21 or did not specify right vs. left or combined^16,19	ONSD asymmetry has been documented in astronauts with SANS¹⁴. Since the presence of findings unilaterally is consistent with SANS under the current working definition⁴¹, averaging asymmetric measurements may lead to underestimating ONSD and missing SANS manifestation.	Eye findings should be reported independently for each eye particularly when diagnostic thresholds are being evaluated or considered.
Reporting means differences in ONSD measurements without reporting actual pre-, in-, and post-flight ONSD means¹⁷	Unable to compare ONSD values to other published values in the literature.	Values for each experimental position or mission profile should be reported and not only mean differences.
Researchers performing measurements were not expertly trained¹⁸ or blinded to the subject’s condition^18,23 leading to overestimation of ONSD measurement in the experimental group	Measurement bias combined with poor anatomic differentiation of acquired image or limited training may lead to falsely elevated ONSD findings in the experimental group.	When possible, measurement for research purposes should be performed by an expert with adequate training that is blinded to the condition under which the image was obtained²¹.
Inflight US ONSD measurements are performed routinely in many astronauts for SANS surveillance⁴². However, findings are published on only 18 astronauts^15,17	Publication gap limits investigators understanding of the effects of spaceflight on ONSD.	Perform a retrospective analysis of available astronaut inflight US ONSD data.