noun
Landolt ring; Landolt C
A ring with a gap, used in visual acuity tests; the patient identifies the direction of the gap.
視力検査では、ランドルト環の切れ目の方向を答えます。
In an eye test, you answer the direction of the gap in the Landolt ring.
Named after the Swiss ophthalmologist Edmund Landolt, who introduced the symbol in 1888.