[Dark adaptation for evaluating visual performance at twilight using the Trendelenburg eyeglasses].

Dark adaptation for testing visual acuity under mesopic conditions can be accomplished with Trendelenburg spectacles. The spectacle frames are in contact with the facial skin at all points, forming a light-tight seal so that no stray light reaches the eyes. The lenses are red filters, admitting no light below 630 nm. When these spectacles are used, adaptation can be performed in a normally lit room.