"Glaucoma affecting each crystalline lens": a long-lost manuscript by Dr. William Mackenzie.

Dr. William Mackenzie was one of the great pioneers of British ophthalmology in the 19th century. We present a newly-discovered manuscript in which Mackenzie described how he performed surgery for bilateral nuclear sclerosis of the lens, in 1842-1843. This case became the focus for a discussion of the nature of "cataract" and "glaucoma" in the fourth edition of Mackenzie's great work, A practical treatise on diseases of the eye. Mackenzie is generally remembered as a great compiler of knowledge, but the text Mackenzie built around this case shows him pursuing original arguments based on his own observation. This case report gives us a vignette of Mackenzie that illustrates aspects of Mackenzie's character and achievements in an intimate way, and it dramatizes in a lively manner how some of the most fundamental concepts in ophthalmology evolved.