Seven-degree head-down tilt reduces choroidal pulsatile ocular blood flow.
Bibliographic record
Abstract
INTRODUCTION: We investigated the effects of head-down tilt (HDT), which simulates microgravity during spaceflights, on the choroidal pulsatile ocular blood flow (POBF). This investigation is important because alterations in the choroidal blood flow can affect the function of retinal rods and cones that rely totally on the choroid for metabolites. METHODS: Nineteen healthy adults between 20 and 38 yr of age participated in this study. The POBF was compared for: 1) baseline, wherein subjects were declined 30 degrees from vertical; 2) microgravity simulation where subjects were in a 7 degrees HDT for 2 min; 3) 90 min of the 7 degrees HDT; and 4) recovery, i.e., back at 30 degrees for 2 min. RESULTS: The group averaged POBF (Mean +/- SEM values: 828.43 +/- 48.88 microL x min(-1)) decreased immediately during the 2-min microgravity simulation (582.18 +/- 43.62 microL x min(-1)), remained at that inferior level at the 90-min mark of HDT (542.26 +/- 45.35 microL x min(-1)), and came back toward baseline POBF during the recovery period (760.11 +/- 46.03 microL x min(-1)) (p = 0.0001). DISCUSSION: The results show that simulated-microgravity of relatively short duration induces retinal hypoperfusion throughout the microgravity interval through the reduction in the POBF. This finding may have important implications regarding visual performance in space crewmembers placed in prolonged microgravity environments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".