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Investigating Optical Lens Theory and Lensometry

Alisa Alexander
Alisa Alexander

At some point in their lifetimes, a majority of people will experience myopia (nearsightedness), hyperopia (farsightedness), presbyopia (age-related farsightedness), astigmatism, or a combination of these conditions. This presentation will explain the biological factors related to these conditions and the physics behind the development of lenses, particularly eyeglasses, to aid vision in these conditions. The prescription of lenses can be read through a lensometer. A manual lensometer, or focimeter, is an optical instrument utilized by an optometrist or optician to establish a patient’s prescription before examination or to verify the correct prescription in a pair of lenses. The machine reads several components of a prescription, the primary three including what many have seen on their printed prescription in the form of three numbers from their doctor: spherical and cylindrical power and the respective axis of a lens. These numbers correspond to whether someone is myopic or hyperopic. They also reveal if someone has astigmatism. The lensometer has not changed drastically since its creation a little over one hundred years ago, when the first lensometer was patented by Dr. Estelle Glancy and her colleague, Dr. Edgar Tillyer.


Alisa Alexander is a senior majoring in Health Science with a minor in Public Health. Her passion lies in optometry. Presently, she is gaining valuable experience through an internship at a local practice. Alisa is eagerly looking forward to furthering her education at the Kentucky College of Optometry at the University of Pikeville this fall to follow her dream of becoming an optometrist.