Fresnel Prisms

Abstract

After 1960, the Fresnel principle, which existed for more than 150 years, was used for the first time to manage strabismus. In 1970, the optical scientific group from San Rafael of California designed a combination of a series of Fresnel press on prisms. These prisms are made up of plastic membranes with powers ranging from 0.5-30 prism dioptres. The Fresnel prism is derived from the concept of hand-ground lenses prepared by the physics and French specialist Augustine Fresnel in 1921. Initially, they were intended for use in lighthouse beacons. Prisms have been used extensively in the field of ophthalmology, especially related to neuro-ophthalmology and strabismus. Prisms are used extensively to increase the binocular field, relieve diplopia, or expand the field of vision. Fresnel prisms are thin transparent plastic membranes with multiple tiny prisms attached from base to base. Augustin Fresnel articulated the optics of Fresnel prisms. The angle of refraction of a prism depends upon the angle of the surface and the refractive index of the material of which the prism is made. The angle of refraction is independent of the thickness of the prism. These offer the advantage of being lightweight and easy to handle. The most common use is to temporarily relieve the diplopia in cases like nerve palsies secondary to trauma, blowout fractures, decompensated phoria, divergence insufficiency, or convergence insufficiency. Fresnel prisms are most commonly used as stuck-on prisms. Traditionally, prisms have also been used in patients with stroke and homonymous hemianopia. The aim is to shift the peripheral image towards the central retinal meridian.