Perhaps the most recognized lens around the world, the Volk 20D is the lens that started the legacy of double aspheric lens design for BIO and is still considered as a gold standard.
The contributing factors for this are the perfect balance of field of view and magnification of the 20D.
The working distance of 50 mm also makes lens manipulation a comfortable experience for the examiner.
This lens is perfect for general diagnosis of patients with a 3x magnification and field of view that allows visualization up to the mid peripheral region.
The dynamic examination with the appropriate eye movements by the patients allows viewing of the peripheral retina as well as detailed examination by BIO in the primary position provides a comprehensive estimate of retinal health. Thus, this lens is a great choice both as a first line of diagnosis as well as a high level central retinal examination.