Evolution and impact of eye and vision terms in written English.

With this article, we aimed to trace the evolution and impact of eye-related terms common in written English during the past 2 centuries by studying digital resources. Eye-related words and phrases (n-grams) occurring in English books at a frequency of 0.00001% for at least 25 years between 1790 and 2008 were identified from the Google n-gram database by searching for 254 strings such as eye or ophth. The first known English use of these n-grams was identified from historical articles and from multiple digital resources. Eye color was not commonly described as brown or green before 1840. Many common bigrams, such as bright eyes, suggested light emanating from the eyes, consistent with the extramission theory of vision. Based on word frequency, the impact of the revolutionary 1850 ophthalmoscope exceeded that of the stethoscope for 60 years. Glaucoma was not commonly written until the ophthalmoscope permitted visualization of the characteristic optic neuropathy. Green spectacles gave way during the early 1900s to dark glasses, subsequently renamed sunglasses. Until the mid-1900s, an eye surgeon was more often described as an oculist than an ophthalmologist, and inflamed eyes were said to experience ophthalmia more often than uveitis. Macular degeneration was rarely written about for more than a century after 1850 because it was labeled choroiditis. Of the 135 n-grams in the dictionary, an earlier written instance was identified in 92 cases (68%). Online databases of the written word reveal the origin and impact of many important vision concepts.