{
  "resourceType": "ActivityDefinition",
  "id": "brock-string",
  "url": "https://bodyiq.dev/fhir/ActivityDefinition/brock-string",
  "version": "1",
  "name": "BrockString",
  "title": "Brock String",
  "status": "draft",
  "experimental": true,
  "description": "A string with 3–5 colored beads is held from the bridge of the nose to a fixed point. The user fixates each bead in sequence; correct fixation produces a single bead with two strings crossing through it (physiological diplopia of the un-fixated beads).",
  "useContext": [
    {
      "code": {
        "system": "http://terminology.hl7.org/CodeSystem/usage-context-type",
        "code": "user"
      },
      "valueCodeableConcept": {
        "text": "difficulty: beginner"
      }
    }
  ],
  "topic": [
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "brock-string",
          "display": "Brock String"
        }
      ]
    }
  ],
  "kind": "ServiceRequest",
  "dosage": [
    {
      "text": "5–10 minutes/day as part of an office-based vergence program (CITT pattern)."
    }
  ],
  "usage": "Evidence: moderate.",
  "note": [
    {
      "text": "When fixating the bead, the other beads should appear doubled — that's the X pattern of physiological diplopia"
    },
    {
      "text": "If one string disappears, that eye is suppressing — close the other and reopen to re-engage"
    }
  ]
}