Domain: Healthcare — Skin Physiology
Target concept: Capillary Refill Test

Video generation prompt: The examiner presses the nail bed with a finger for several seconds and then releases the pressure. The video demonstrates the hand at rest, the pressing action, and immediate release, with a focus on the fingertips and nail bed.

Evaluation guide:
(i) Target concept: Capillary refill as a dynamic, localized, reversible response to mechanical compression of nail bed capillaries.
Minimum mechanism: Intact dermal microvasculature with functional precapillary sphincters, patent capillary loops beneath the nail plate, and intact autoregulatory vasodilation upon pressure release.
(ii)Storyline: [Phase 1: Baseline] Hand stationary, nail bed fully visible, exhibiting natural pinkish-red color with uniform hue and no pallor. [Phase 2: Compression] Examiner"s finger makes full, stable contact on nail bed; color immediately and completely desaturates to uniform pallor across entire nail bed surface. [Phase 3: Release & Refill] Examiner"s finger fully withdraws; within one continuous visual interval, pinkish-red color reappears as a single advancing front originating at distal edge and progressing proximally without interruption, gap, or asymmetry. Perspective must maintain fixed frontal/slightly oblique view of nail bed throughout; no occlusion, zoom, or repositioning allowed. Visibility requires unobstructed, in-focus, well-lit view of nail bed surface and immediate surrounding tissue for contrast reference.

Manual:
Experimental Procedure
1. Position hand at rest with fingers extended and nail beds facing camera.
2. Examiner places fingertip directly onto subject"s nail bed and applies firm, even pressure for several seconds.
3. Examiner instantly releases pressure and withdraws finger.
Observation of Experimental Phenomena
During pressure: nail bed becomes uniformly pale/white (pallor).
After release: pinkish-red color returns as a continuous wave moving proximally from distal nail edge (capillary refill).
Summary of Experimental Principles
Capillary Refill Test assesses peripheral perfusion and vascular responsiveness. Pallor reflects transient capillary compression; refill time and pattern reflect microcirculatory integrity and autonomic regulation.

Prompt Grounding rubric:
level_1: No hand or fingertip is shown; or no nail bed is visible at any point; or the video never shows a pressing action; or never shows a release; or the hand is not at rest at the very start; or unrelated subject matter (e.g., face, instruments, other body parts) dominates the frame instead of the fingertip.
level_2: A hand and nail bed are shown, but the viewing angle hides the nail bed for a meaningful stretch (e.g., palm-up, side-on, or a steep angle); or only one of the three phases (rest, press, release) is actually shown on screen while the others are implied or happen off-camera; or the pressing contact lands somewhere other than the nail bed (e.g., the fingertip pad or the skin beside the nail).
level_3: The hand at rest is shown with a clear frontal or slightly angled view of at least one nail bed; a finger is shown making contact on the nail bed; the finger is then shown fully lifting away; and these three phases happen in the correct order (rest, then press, then release) within the shot.
level_4: Everything in the 3-point description holds, and in addition the nail bed stays centered and in focus through all three phases, no extra hands, tools, or other people or objects intrude into the frame at any point, and the pressing finger's contact and withdrawal are visually unambiguous throughout, whether the pressing hand belongs to the same person (self-test) or a second person.
level_5: Everything in the 4-point description holds, and in addition the fingertip stays steady in the frame with no panning, zooming, or shakiness; the nail bed is fully visible with no shadow, glare, or skin fold hiding part of it; the pressing finger contacts mainly the nail plate itself rather than spreading heavily onto the surrounding fingertip skin; and the release happens as one clean, complete motion rather than a slow or partial withdrawal.

Scientific and Causal Correctness rubric:
level_1: The nail bed never changes color at any point; or it stays uniformly an abnormal color throughout (e.g., white, blue, or purple) with no visible transition; or the color change happens only before the press or only after the release rather than tied to the press-then-release sequence; or the color change happens somewhere other than the nail bed (e.g., only the fingertip pad).
level_2: Pallor appears during the press but unevenly across the nail bed (e.g., only half blanches); or the pink color starts returning before the finger has fully lifted; or the returning color is clearly the wrong shade (e.g., bright red or yellowish rather than pink); or the color returns to one side of the nail bed but not the other with no visible reason.
level_3: The nail bed turns evenly pale while pressed, the pallor clears after the finger lifts, and the pink color comes back as a visible band moving from the tip of the nail toward the cuticle, without gaps or skips, staying confined to the nail bed; the resting hand shows no color change before the press begins.
level_4: Everything in the 3-point description holds, and in addition the pallor covers the entire nail bed with no pink patches showing during the press, the pink color starts returning as soon as the finger is fully off the nail with no noticeable pause, and it returns as one connected band rather than scattered spots or separate fronts.
level_5: Everything in the 4-point description holds, and in addition the returning color spreads evenly across the full width of the nail bed as it advances, the nail bed's final color matches its color before the press (same hue, not left redder or bluer than baseline), and no unrelated color artifact appears, such as a visible pulse, pooling, or skin-wrinkling effect that changes color independent of the pressure test.

Spatiotemporal Consistency rubric:
level_1: The hand or examiner's finger jumps to a different position or angle with no continuous motion between; the nail bed vanishes and reappears; the lighting suddenly flashes, strobes, or goes dark for no reason; or a body part visibly breaks apart or bends in an anatomically impossible way.
level_2: There is a noticeable shake or wobble that does not quite break the shot's continuity; the pressing finger blocks the nail bed for a brief, barely noticeable instant while lifting away (well under a second, not a sustained block); the picture loses focus and blurs enough to hide the nail bed's texture for a stretch of the video; or shadows on the hand look like they come from more than one light source or shift direction with nothing else moving.
level_3: There is no jumping, vanishing, or sudden lighting change, and no visible warping or shearing of the hand or finger; the nail bed stays fully in view and intact the whole time; the examiner's finger moves in a physically ordinary way (no floating, clipping through the nail, or unnatural joint bends); and the background behind the hand stays static.
level_4: Everything in the 3-point description holds, and in addition the examiner's finger's press-and-release motion looks smooth and natural (no sudden speed-up, reversal, or freezing partway through), the nail's curve and shape stay consistent rather than flattening or bulging oddly under pressure, and there is no flicker or strobing in the shot.
level_5: Everything in the 4-point description holds, and in addition the motion is fluid across the whole clip with no stutter or dropped-looking frames, the fingertip and surrounding skin move together with no visible sliding or misalignment between them, the nail's edges stay straight and true rather than bowing or warping, and the sense of depth between the nail, finger, and background stays consistent with no layer appearing to float free of the rest.