Chromatic aberration, addressed in this study is based on the character of dispersion of material, of meaning that refractive index changes with wavelength. Fundamental knowledge of dispersion, the method of negating chromatic aberration, and the Abbe number are explained. The results of researches into chromatic aberration of the eye’s optical system are then introduced collectively. Also shown are simulated retinal images of eyes with aspheric IOL and achromatic IOL based on the results of these researches. From presumably perceived images, it was found that spherical aberration and chromatic aberration decrease image contrast and increase depth of field.
Chromatic aberration is related to the visual and physiological functions of the eye in various aspects. In human optics, the cornea and lens are the eye structures mainly related to chromatic aberration. In pseudophakic eyes, the difference in chromatic aberration due to the difference of the intraocular lens material may affect visual function. Recently, it was reported that the hybrid singlet achromatic IOL design, with a combination refractive and diffractive surfaces for resolving spherical and chromatic aberration problems, improved the optical quality and that the polychromatic modulation transfer function (MTF) in an eye with a centered, not tilted achromatic IOL was near the diffraction-limited MTF. However, reduction of chromatic aberration would contribute not only to increase in contrast of the retinal image, but also to decrease in depth of field. Further investigation is therefore needed, so as to decide whether or not chromatic aberration should be controlled.
We are developing a new imaging system by which neural activity in the retina can be noninvasively measured (functional retinography: FRG). We believe that this is a new step in the investigation of basic retinal physiology, and toward the development of a diagnostic tool for noninvasively detecting early and minor retinal dysfunction.
In recent years, hospital medical records are becoming increasingly computerized; many hospitals are working on introducing electronic ordering systems and medical records. In ophthalmology, due to its unique practice pattern, however, various problems have arisen regarding use of the general hospital system. To find solutions to these problems, a system for the department of ophthalmology is currently being introduced that will operate continuously with the overall hospital system. We introduce solutions achieved by this system for the ophthalmology department, using some introductory examples.
We measured refraction using a newly developed simultaneous binocular autorefraction device (BV-1000, Topcon) and compared the measurements with those obtained using a conventional monocular autorefractometer (KR-8100A, Topcon). Children with ametropic amblyopia without strabismus (15 patients, 30 eyes, 5.6±1.6 years old), anisometropic amblyopia (10 patients, 20 eyes, 7.6±3.3 years old), without amblyopia (20 patients, 40 eyes, 7.4±3.6 years old) and adults (10 patients, 20 eyes, 34.6±7.8 years old) were evaluated. Objective refraction before and after instillation of 1% cyclopentolate was measured using the two devices. In each group with and without amblyopia, the difference between pre- and post-cycloplegic refractive values was significantly smaller in BV-1000 measurement than in KR-8100A measurement. In anisometropic amblyopia, regarding the disparity between fellow eyes, the differences between pre- and post-cycloplegic measurements varied less in BV-1000 measurement than in KR-8100A measurement. Use of the BV-1000, enables accurate measurement of anisometropia without cycloplegia.
We analyzed the relationship between subjective and objective refractions preoperatively and at 6 months after myopic laser in situ keratomileusis (LASIK) in 30 eyes of 15 patients aged 22 to 39 years (mean ± standard deviation, 29 ± 5). The amount of correction was −1.5～−8.38D (mean ± standard deviation, −4.09 ± 1.89D). Subjective refraction was measured by the second method of subjective refraction. Non-cycloplegic and cycloplegic objective refraction were measured by autorefractometer and aberrometer. Corneal and ocular aberrations for 4 and 6 mm diameter pupil were measured by aberrometer. There was no significant difference between refraction values preoperatively. Postoperatively, the order from plus to minus was as follows: cycloplegic autorefraction, subjective refraction, cycloplegic refraction for 4 mm pupil measured by aberrometer, noncycloplegic autorefraction and cycloplegic refraction for 6 mm pupil measured by aberrometer. Cycloplegic autorefraction and subjective refraction were significantly more positive or less negative than noncycloplegic autorefraction. It is suggested that after myopic LASIK, measurement through a wider pupil area results in more negative value of refraction, being affected by spherical-like aberration.