"Landolt C" meaning in English

{
  "etymology_text": "Developed by the Swiss-born ophthalmologist Edmund Landolt.",
  "forms": [
    {
      "form": "Landolt Cs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Landolt C (plural Landolt Cs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with language name categories using raw markup",
          "parents": [
            "Entries with language name categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A ring with a gap in it, used as a symbol in vision tests."
      ],
      "hypernyms": [
        {
          "word": "optotype"
        }
      ],
      "id": "en-Landolt_C-en-noun-j2pURSjz",
      "synonyms": [
        {
          "word": "Landolt broken ring"
        },
        {
          "word": "Landolt ring"
        }
      ],
      "wikipedia": [
        "Landolt C"
      ]
    }
  ],
  "word": "Landolt C"
}

{
  "etymology_text": "Developed by the Swiss-born ophthalmologist Edmund Landolt.",
  "forms": [
    {
      "form": "Landolt Cs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Landolt C (plural Landolt Cs)",
      "name": "en-noun"
    }
  ],
  "hypernyms": [
    {
      "word": "optotype"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English entries with language name categories using raw markup",
        "English eponyms",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with non-redundant non-automated sortkeys"
      ],
      "glosses": [
        "A ring with a gap in it, used as a symbol in vision tests."
      ],
      "wikipedia": [
        "Landolt C"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "Landolt broken ring"
    },
    {
      "word": "Landolt ring"
    }
  ],
  "word": "Landolt C"
}