George Lindsay Johnson received his schooling at Amersham Hall (near Reading) and in Bonn and Stuttgart, Germany. As a result he became fluent in German and French. After spending a year on a ranch in Australia, where he had relatives, he studied at Owen's College (in Manchester) and at Caius College (University of Cambridge), obtaining a Bachelor's degree (either BA or BS) in 1875 and the degree Master of Arts (MA) in 1880. Continuing his studies in medicine at St Bartholomew's Hospital, London, he qualified as Bachelor of Medicine (MB, 1882), Fellow of the Royal College of Surgeons of England (1884), and Doctor of Medicine (MD, University of Cambridge, 1890).
Johnson specialised in ophthalmology and early in his career invented several optical instruments, including an improved ophthalmoscope that he described in 1882, a timing shutter device for experiments on the duration of colour sensations (1889), and a macula sensitometer. He published numerous papers on medical and related subjects, also in German and French journals, though his main interest remained the study of the eye. He served as registrar at the Royal Westminster Ophthalmic Hospital, London, for several years during the eighteen-nineties. During this period he spent much time at the zoological gardens in London, studying the comparative anatomy of the eye in some 180 living species of mammals. Among others he published papers on the eyes of seals (1893), the pupils of the felidae (cat family, 1894) and the eyes of primates (1897) in the Proceedings of the Zoological Society of London. This work culminated in a comprehensive publication, "Contributions to the comparative anatomy of the mammalian eye, chiefly based on ophthalmoscopic examination" (Philosophical Transactions of the Royal Society of London, 1901, Vol. 194, 82 pp). His best known book on ophthalmology was a very convenient Pocket atlas and text-book of the fundus oculi (1910, 1914). After leaving the Royal Westminster Ophthalmic Hospital he filled various other positions, including that of surgeon to New College, consulting ophthalmic surgeon at the Western General Dispensary, and ophthalmic surgeon at the West End Hospital for Nervous Diseases, London.
In addition to ophthalmology Johnson became an expert on colour photography. He published two of the first books on the subject, Photographic optics and colour photography, including the camera, kinematograph, optical lantern and the theory and practice of image formation (London, 1909, 332 pp) and Photography in natural colours (London, 1910). The latter became a standard text, with a sixth edition published in 1922.
Johnson emigrated to South Africa in 1911 and started a practice in Johannesburg. In 1916 he moved to Durban, where he practised until his retirement in 1930. He continued his research in comparative anatomy, producing a comprehensive paper titled "Contributions to the comparative anatomy of the reptilian and amphibian eye" (Philosophical Transactions of the Royal Society of London, 1924, Vol. B215, 49 pp). Later he documented the distressing visual sensations from which he had suffered for most of his life, in "Subjective visual sensations" (Archives of Ophthalmology, 1936). He also wrote papers for local medical journals. These included articles on the treatment of chronic trachoma (Transvaal Medical Journal, 1913, Vol. 8) and glaucoma (Medical Journal of South Africa, 1913, Vol. 9); "Two curious optical illusions" (Journal of the Medical Association of South Africa, 1927, Vol. 1); "Correction of conical cornea by contact glasses" (ibid, 1930, Vol. 4); and a letter to the editor on the treatment of the detachment of the retina (ibid, 1931, Vol. 5). He served as ophthalmic surgeon to the military forces in Durban and held the rank of captain in the South African Medical Corps.
Johnson's contributions to ophthalmology and colour photography were widely recognised. He was elected an Honorary Fellow of the Royal Society of Research in Berlin, a Fellow of the American Academy of Ophthalmology and Oto-Laryngology, a Fellow of the Royal Photographic Society, London, and a Fellow of the Royal Society of Italy. He became a member of the South African Association for the Advancement of Science in 1912 and in 1916 read a paper at its annual congress titled "On certain remarkable resemblances between the formation of images and colour-vision in man and certain vertebrate animals". Only the title was published in the association's Report for that year.
Outside his fields of expertise Johnson interested himself in a wide variety of topics. For example, he wrote articles on "The origin of the dog" (South African Kennel Gazette, December 1927) and "What it feels like to be drowned" (Outspan, 24 March 1939). He also held prospecting rights on a portion of land in the northern Karoo where indications of oil were found. In later life he became interested in spiritualism and wrote a letter to the editor of the Journal of the Medical Association of South Africa (1931, Vol. 5) on a supposed unknown power that can cause table rapping and move objects during sceances. He also wrote a novel, The weird adventures of Professor Delapine of the Sorbonne (1916).
Johnson married Emily Maria Schreiber, with whom he had two sons, both of which were killed during World War I (1914-1918). He later married Eliza Susan Klinck (born Rooth), with whom he had one son. She died in 1923.