- You may be also be looking for VISOR, a 24th century medical device used to aid the blind.
A specially designed visor was used to shield the eyes of humanoids who may look upon Medusans in order to prevent the insanity that would otherwise result from their hideous appearance. It proved to be especially effective for Vulcans. (TOS: "Is There in Truth No Beauty?")
The Troglyte miners on Ardana also wore special visors for unknown reasons that could be related to their harsh work environment in the Zenite mines. (TOS: "The Cloud Minders")