Diffractive Contact Lenses Research Articles

Chromatic changes in vision with diffractive ophthalmic optics.

Diffractive optics is a valuable technique for designing presbyopia-correcting lenses, but its effectiveness is wavelength-dependent. This study investigates the spatio-chromatic alterations in visual resolution associated with diffractive multifocal lenses by using non-invasive, removable diffractive bifocal contact lenses. The study combines theoretical analysis, numerical simulation, and clinical intra-observer experiments to assess visual acuity under various lighting conditions. Results demonstrate the introduction of spatio-chromatic asymmetry and a change in visual acuity under red and blue lights, depending on the operating diffraction order employed in the lens design. The energy distribution of the diffractive contact lens studied favors resolution under red illumination at far distances and under blue illumination at near distances. These findings are consistent with computational simulations and provide insights into the visual changes induced by diffractive ophthalmic lenses.

Chromatic aberration and optical power of a diffractive bifocal contact lens.

Although diffractive contact lenses have been well documented in theory, no definitive experimental data have been reported which confirm that the near image is in fact created by diffraction rather than by refraction. We have tested the diffraction hypothesis for one type of diffractive contact lens (the Hydron Echelon bifocal) experimentally by measuring its longitudinal chromatic aberration in isolation and when worn on the eye. The basis of this test is that, according to theory, diffractive lenses should have chromatic aberration which is opposite in sign to that measured for the eye. Objective measurements of chromatic aberration were made with a focimeter when the lens was in a wet cell. Subjective measurements were made with a Badal optometer when the lens was worn on the eye. Four control experiments were conducted to provide baseline measurements of the eye's chromatic aberration, against which we compared the results obtained for the diffractive contact lens. The data were also compared with conventional measurements of refractive error obtained by standard subjective techniques and by an automated infrared refractor. Our results showed that the longitudinal chromatic aberration of the diffraction image of the Echelon bifocal lens was about one-half that obtained under the four control conditions: for the naked eye, for the nondiffraction image of the Echelon lens, or for either image of a refractive bifocal contact lens (CIBA Bisoft). These results are consistent with the theoretical prediction that the negative chromatic aberration of a diffractive contact lens should partially cancel the positive chromatic aberration of the human eye.(ABSTRACT TRUNCATED AT 250 WORDS)