The importance of painstaking care and accuracy in determining the refraction of the eye is well understood by the ophthalmologist of to-day. Indeed, in America, those in the front rank in every department of medicine recognize the great value, for the relief of many disturbing conditions, of accurately correcting refractive errors. Any suggestions which may render results more certain are of value, and the careful ophthalmologist will spare no effort to reach a decision as nearly correct as possible, well knowing that what appears to be a slight error in the measurement of any eye's refraction may render valueless the work of making the measurement, and cause a failure of his attempt to relieve a patient of some distressing condition.
The question of illumination, the position of test types with reference to patient and light, and even the arrangement of the case of test lenses, all are worthy of attention.
STARR EG. A MODIFIED FORM OF TEST-CARD AND TEST-LETTER.. JAMA. 1902;XXXIX(19):1156-1158. doi:10.1001/jama.1902.52480450006002