The Implantable Collamer Lens (ICL) is a posterior chamber phakic intraocular lens. Two types of ICL, one with sphere correction, the other with sphere and cylinder correction, heve been approved in Japan. Regarding the outcomes of ICL implantation, high efficacy, predictability and safety have been reported in Japan and other countries. Considering that the surgeries are performed on healthy eyes, proper selection of patients, sufficient preoperative examination and safe surgery are necessary to achieve successful results in ICL surgery. Sufficient anterior chamber depth is required for safe ICL surgery. Accurate refraction test and ICL size determination are especially important in the preoperative examination. Although the surgery itself is simple, the surgeons must be skilled in intraocular surgery. During the surgery, avoidance of damage to crystalline lens and corneal endothelial cells is important. Immediately after surgery, the surgeon should carefully other to ensure that pupillary block has not occurred, and that lens size is appropriate. Long-term follow-up is needed to watch for the onset of cataract formation.
Series expansion of wavefront aberration by Zernike polynomials and their orthonormalization process are described. We can easily calculate the Zernike series coefficients of any wavefront aberration, and can immediately count, for example, the contribution of each polynomial to the RMS (root mean square) wavefront error. We explain the merit of using Zernike polynomials, with analogy to the orthonormal system of two-dimensional planar vector space. It is convenient if Zernike polynomials are arranged in the so-called ‘fringe order,’ since the lower order polynomials are then equivalent to Seidel aberrations.
Gabor patterns have been popularly used in visual psychophysics, primate physiology and brain imaging, since the patterns can be manipulated in spatial and spatial frequency domains independently. However, Gabor patterns are known to have some inconvenient characteristics that the perception of the size of the Gabor pattern depends on the envelope contrast of the pattern. We investigated this phenomenon in detail. We measured contrast thresholds of perceived size discrimination a test and a reference Gabor pattern (σ=0.625 degree, 8 cpd-carrier). We varied reference pattern contrast from 10.0 to 80.0% at four orientations (0, 45, 90, 135 degrees) of the Gabor carrier component. We tested the upper and lower thresholds at which observers could discriminate the difference in perceived size by chance. All thresholds increased with increasing contrast of the reference Gabor pattern, but the steepness of the threshold functions differed between the upper and lower thresholds. We found an asymmetrical property of size perception that is dependent upon Gabor pattern contrast.
Depth of field (DOF) after cataract surgery was calculated using ray tracing and diffraction integral, with a coaxial, rotationally symmetrical optical model. The effects of optotype, optotype size, entrance pupil size, correction method (glasses, contact lenses (CLs), spherical intraocular lenses (IOLs), aspheric IOLs) and retinal contrast sensitivity were examined. Landolt’s optotype DOF was larger than that of four rectangular optotypes. The larger the optotype or the higher the retinal contrast sensitivity, the deeper the DOF. When pupil size was around 1.5mm, DOF was large and pinhole effect was confirmed. When pupil size was smaller than 2.5mm, DOF was the same in different correction methods. When pupil size was larger than 2.5mm, DOF was large in descending (i.e.; CLs > spherical IOLs > •••••) order of CLs, spherical IOLs, aspheric IOLs and glasses. Calculated DOF coincided well with the values in previous clinical reports. The amount of pseudo-accommodation is thought to be optically calculable and predictable.