This section is from the book "The Home Hand-Book of Domestic Hygiene and Rational Medicine. Volume 2.", by J. H. Kellogg, M.D.. Also available from Amazon: The Home Hand-Book of Domestic Hygiene and Rational Medicine, Volume 2.
This is a condition in which the eyeball is too short, as shown in Fig. 451. Persons whose eyes are in this condition usually suffer with great fatigue after a long use of the eye, generally with slight pain or heavy feeling in the forehead. When reading at night, the print soon becomes blurred. After resting the eyes awhile by closing them, or by rubbing or bathing them, the reading may be continued, but the eyes soon become again fatigued. In some cases the individual is utterly unable to read fine print at any distance, and is also unable to see clearly objects some distance away. Persons suffering in this way were formerly considered incurable; but it is now very well known that the defect is easily corrected by means of convex glasses, such as are used for old-sight. The discovery of this fact was made accidentally, after thousands of individuals had been compelled to go through life with continual suffering, under the idea that the weakness of sight was due to commencing blindness, which would be greatly intensified by wearing glasses of any sort. In former times, if a longsighted child happened to discover that he could read more easily with his grandmother's spectacles, they were quickly snatched away from him, as though they were a dangerous weapon in his hands.
Fig. 451. Eye ball of Long-sighted Eye.