Electroholography is a technology that displays three-dimensional images using electrocommunication. Because it has the potential to satisfy the physiological aspects of vision, such as parallax, convergence and focusing, electroholography is often said to be the ideal three-dimensional display. However, it has never been commercially realized because of technical difficulties. Recently, there have been advanced developments in microfabrication and computers, which are used in electroholography. The first electroholographic system, proposed by Professor Benton’s group (Massachusetts Institute of Technology) in 1990, showed color three-dimensional movies. The system had strong impact on the field, and indicated the capabilities of electroholography. Subsequently, many researchers were inspired, and attempted to make various systems. Last year, a prototype using a new method was developed. Although it is still not the ideal electroholography, it shows commercial potential. This paper reports on the progress of electroholography, problems be resolved, and prospects for the future.
Acrylic aspherical intraocular lenses (IOLs) heve become popular and are widely used, since small incision surgery can be done, using thinner acrylic lenses with high refractive index. However, the Abbe number of acrylic is smaller, which means that acrylic lenses have larger chromatic aberration. The advantage in making the spherical aberration 0μm is to obtain the highest contrast at the focus position. However, the highest contrast cannot be expected in other than the focus position. On the other hand, optics with spherical aberration have a wide resolution range. It is said that image quality becomes bad when astigmatism remains after surgery. Here, using images made by several simulations, we show the characteristics of aspherical IOLs.
Purpose: To compare axial length (AL) readings between partial coherence interferometry (PCI) and ultrasound A-scan (US) in patients with epiretinal membrane (ERM).
Methods: Forty eyes with ERM were enrolled. AL was measured by PCI and US; foveal thickness (FT) was measured using optical coherence tomography. The double peak (DP) and distance between peaks recognized in PCI measurements, and AL disparity between PCI and US, were compared to FT. Postoperative refractive error with DP posterior peak used for intraocular lens (IOL) power calculation was evaluated.
Results: DP was found in 14 eyes (35.0%). The distance between the two peaks was significantly correlated with FT. The difference in AL between PCI and US was not significantly correlated with FT. The percentages of postoperative refractive error within ± 1.0D were 95.0% and 90.0% using PCI and US, respectively. If anterior peak is used in IOL power calculation, postoperative refractive error will be more myopic than anticipated.
Conclusions: This study indicates that PCI is comparable to US in patients with ERM; however, measurement using posterior peak is more accurate in calculating IOL power when DP is identified.