<prompt> Illuminated Frenzel glasses are used in detectingNystagmusHeterophoriaEsotropiaAstigmatism  <response>: Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 358 - 362Illuminated Frenzel glasses 20 lenses are useful for abolishing fixation and thus revealing peripheral vestibular nystagmus 