{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://openvisual.org/schema/peripheral-tremor/1.0",
  "title": "OVS: Peripheral Tremor",
  "description": "Oscillation of the visual field outside a stable centre: the central field stays steady while the periphery moves back and forth, typically for minutes (e.g. after waking). Visual snow in the affected zone is often reported as coarser, denser and more agitated. A localized form of oscillopsia; HPO Tremor (HP:0001337) is listed as frequent in VSS (Orphanet ORPHA:420556). `severity` is the oscillation amplitude (1 = 2% of the visual-field width).",
  "allOf": [
    {
      "$ref": "https://openvisual.org/schema/symptom-base/1.0"
    },
    {
      "type": "object",
      "properties": {
        "ovs_type": {
          "const": "ovs:peripheral-tremor"
        },
        "frequency_hz": {
          "type": "number",
          "minimum": 0,
          "description": "Oscillation frequency in Hz"
        },
        "direction_deg": {
          "type": "number",
          "minimum": 0,
          "maximum": 180,
          "description": "Axis of the oscillation in degrees; 0 = horizontal, 90 = vertical"
        },
        "motion": {
          "type": "string",
          "enum": [
            "linear",
            "circular",
            "jitter"
          ],
          "description": "linear = back and forth along the axis; circular = elliptical; jitter = irregular, multi-frequency"
        },
        "center_radius": {
          "type": "number",
          "minimum": 0,
          "maximum": 1,
          "description": "Radius of the stable central field as a fraction of the smaller field dimension (0 = whole field affected)"
        },
        "transition_width": {
          "type": "number",
          "minimum": 0,
          "maximum": 1,
          "description": "Width of the gradual transition from the stable centre to the oscillating periphery, same unit as center_radius"
        },
        "snow_intensification": {
          "type": "number",
          "minimum": 0,
          "maximum": 1,
          "description": "How much denser, coarser and more agitated visual snow is inside the tremor zone (0 = unchanged)"
        },
        "episode_duration_min": {
          "type": "number",
          "minimum": 0,
          "description": "Typical episode duration in minutes; 0 = continuous"
        }
      }
    }
  ]
}