HISTORICAL PERSPECTIVE ON THE DIFFICULTIES OF HYPERMETROPIA
By C. H. BROWN, M. D. 1921

A concave lens is a negative lens and diminishes refraction; a hypermetropic eye is one in which there is naturally a deficiency of refraction. Now if we consider these two facts together, it follows that a concave lens placed before an emmetropic eye will lessen its refraction, and to that extent will make it equivalent to, and place it in the same optical condition as a hypermetropic eye.

Therefore if any one enjoying emmetropic eyes desires to experience a practical demonstration of the difficulties and hindrances which are ever present to annoy and harass the hypermetrope, he can very easily place his own eyes in the same condition by making them artificially hypermetropic by the use of concave lenses.

If he tries first weak lenses and by changing them gradually increases their strength, he will in the beginning find that by the exercise of his accommodation he is able to neutralize and overcome the diminishing effect of the concave lenses. 

As, however, he gets into the higher numbers, it becomes a more and more difficult task for the accommodation to counterbalance these increasing negative lenses.

If, in spite of these warnings that the accommodation has reached the extreme limit of its powers, and its greatest effort is required to preserve vision clear through the concave lenses, a step farther be taken with stronger glasses, it would entirely drain all the resources of the ciliary muscles, and they would be no longer equal to the task of supplying the necessary refractive power, and vision would become blurred, and the eyes would be in a condition of absolute hypermetropia.

Convex lenses sufficiently strong placed before the concave ones, would supplement the exhausted accommodation, and would partly or wholly nullify the diminishing effect of the concave lenses, and distant vision would again be restored clear and distinct.

 ________________________________

This information is NOT meant to be a substitute for professional assistance. Always follow the instructions provided by the proper professionals.

Use of this site is governed by our Terms of Use Agreement and Privacy Policy.