Myopia (nearsightedness) is the most prevalent of all eye disorders. Many causes have been suggested for myopia ranging from heredity, nutritional deficiency, hormonal imbalance and childhood fever to excessive accommodation (focusing of the eye on close objects) and near work, such as studying. The experiments proposed here are intended to shed light on several of the variables that may cause or exacerbate this disorder. The subjects of these experiments are domestic chicks. These inexpensive and plentiful animals have eyes that are very similar to those of humans in many features, including excellent vision. We have devised a technique for producing experimenttal myopia in chicks by degrading their retinal images during their development. Among the variables to be examined are the effects of near work (close examination of an object with fine details), elevated eye temperature, as might occur in a childhood disease such as measles or eye inflammation, the effects of prolonged accommodation induced by electrical stimulation of the brain region that controls this function and the effects of deficiencies of calcium and vitamin D, which are important for the structure of the sclera (the tough coat of the eye), elongation of which is the cause of the common form of myopia. Not only does the chick provide an excellent model in which to study the causes of myopia, it also can provide a suitable preparation to investigate new and improved methods of treatment, especially by surgical intervention.
