The Array multifocal lens--functional principle and clinical results

BACKGROUND: Common refractive bifocal IOLs feature 2 or 3 spherical zones with different refraction; the design of the Array multifocal IOL consists of 5 concentric zones, each of them providing a progressive near addition with multiple foci by means of an aspherical surface. METHODS: As a part of a prospective study, distance and near visual acuity, contrast sensitivity, glare and depth of field were examined in 15 patients with the Array lens and a monofocal control group 12 months after implantation. Subjective assessment of the optical quality was performed by detailed asking for optical symptoms. Results were retrospectively compared with the one year follow-up of 15 patients with diffractive bifocal IOLs. RESULTS: No difference was found for best corrected far and near visual acuity and sensitivity for high contrasts. Glare and sensitivity for low contrasts of the monofocal IOL was significantly superior to both multifocal models. Array IOL and diffractive IOL achieved a near acuity of Nieden 2-1 with only distance correction; defocus curves revealed an increase in the depth of field, but with a superiority of the Array lens in intermediate imaging. Optical symptoms as halos were much more frequent in patients with the diffractive IOL than in the Array group. CONCLUSIONS: Functional results of the Array multifocal IOL seem to be comparable to those of the diffractive bifocal IOL, but with the advantage of an improved intermediate imaging and a reduction of optical side effects.     

Compared optical performances of multifocal and monofocal intraocular lenses (contrast sensitivity and dynamic visual acuity)

The functional results (contrast sensitivity and dynamic visual acuity) of 19 multifocal (3M design) and 14 all polymethylmethacrylate biconvex monofocal intraocular lenses (IOLs), 6 mm in optical diameter were compared. Best corrected visual acuity was > or = 8/10 (Monoyer chart) Parinaud 2 in all cases. Major differences of functional performance in favour of monofocal IOLs were found outside standard conditions of vision (low contrast and illumination levels). A significant difference in contrast sensitivity was found for each spatial frequency in favour of multifocal IOLs (0.0016 < p < 0.05). Mesopic vision was statistically higher in the monofocal IOL group (p = 0.0015). Moreover, dynamic visual acuity allowed accurate evaluation of the difference in performance between these two models of implant. In view of these results multifocal IOLs should be reserved for patients with normal psychosensitive adaptation; an ocular pathology that could alter contrast sensitivity or mesopic vision is a contraindication for multifocal IOLs.     

Posterior capsule polishing with the neodymium:YLF picosecond laser: model eye study

PURPOSE: To determine the ability and threshold energy of the neodymium:yttrium-lithium-fluoride (Nd:YLF) picosecond laser to achieve micron-level polishing of a latex posterior capsule facsimile (PCF) as an alternative to laser capsulotomy to treat posterior capsule opacification. SETTING: University of Rochester Medical Center, Rochester, New York, USA. METHODS: A solid-state, mode-locked Nd:YLF picosecond laser was used to polish a latex PCF in contact with a poly(methyl methacrylate) intraocular lens (IOL) in an experimental model eye. Eight study groups were treated at different energy levels ranging from 5 to 15 microJ. All treatments were done at least three times in different latex capsules and lenses. An atomic force microscope was used to measure IOL damage and an interferometric surface analysis microscope to assess the polishing effect on the PCF. The IOLs were further subjected to a scatter analysis to assess the optical significance of the damage produced. RESULTS: The latex PCF revealed a polishing effect with all energy settings used. The IOLs were damaged with all energy settings but 5 microJ. Energy settings higher than 5 microJ caused significantly more polishing effect to the latex and damage to the lenses. At the 10 microJ energy level, a single parameter with no depth produced a relative polishing depth of 3.01 microns +/- 0.10 (root mean square +/- SD). At this energy, the damage to the IOLs was 188 +/- 20.52 nm, and it was associated with typical craters over the surface at regular intervals that corresponded to each individual laser pulse. CONCLUSION: This model documented the feasibility of achieving micron-level precision in excising material with the picosecond laser and showed that posterior capsule polishing should be feasible and safe in human eyes.     

Theoretical and practical performance of a concentric bifocal intraocular implant lens

Some results from a survey of 43 patients who had a monofocal intra-ocular-lens (IOL) in one eye and a concentric bifocal intra-ocular-lens in the fellow eye are reported. Twenty patients with 6/9 or better post-operative visual acuity in both eyes, participated in the main part of the study. Optical transfer functions for the bifocal lens showed that, compared to an optimal single-vision correction, there is a 50% contrast degradation of the distance retinal image across all spatial frequencies above around 3 c/deg. For the patients in the main study, there was a close correspondence between practical measurement of contrast sensitivity and the theoretical predictions of the modulation transfer functions. Measuring contrast sensitivity proved an effective means of assessing misalignment of the bifocal IOLs.     

Multifocal rod electroretinograms

PURPOSE: To assess the feasibility of obtaining reliable multifocal rod electroretinograms (ERGS) and to compare them to full-field ERGs. METHODS: Multifocal rod ERGs were recorded using a stimulus array of 61 hexagons. The minimum number of dark, blank frames between flashes was varied from 0 (a minimum of 13.3 msec between flashes) to 21 (a minimum of 293 msec between flashes). Full-field ERGs were obtained using trains of flashes designed to simulate the multifocal sequences. Flashes were blue (W47B), except in a few cases in which red (W26) was used to check for cone intrusion. Flash intensities varied from -1 to 1.7 log scot td-s. RESULTS: Dark-adapted, multifocal ERGs to blue flashes had a small, early component followed by a larger, late component. The early component showed little change in amplitude with increasing intensity. Comparisons with the full-field ERGs indicated that the early component was the focal response. The larger, late component was the response to stray light, and it can be suppressed with the addition of a surround. The focal response was from a relatively circumscribed retinal region. This is shown by comparing the multifocal rod responses from a patient with retinitis pigmentosa to her behaviorally measured rod visual field. CONCLUSIONS: By choosing conditions (namely, flashes of moderate intensity with a surround) to minimize the effects of stray light, multifocal rod ERGs can be recorded with sufficient localization to be clinically useful. However, the signal-to-noise ratio of these multifocal rod ERGs was poorer than for multifocal cone responses for comparable recording periods because of the need for blank frames and the slower recovery of the rods to successive presentations.     

Absorption in a paraboloid of revolution-shaped welding or drilling cavity irradiated by a polarized laser beam

Energy flux absorbed by a paraboloid of revolution-shaped cavity subject to a focused polarized laser beam is systematically and quantitatively investigated. The incident flux is considered to be TEM₀₀ mode of a Gaussian distribution specified by the wavelength, spot size, and focal location of the laser beam. By neglecting absorption and scattering within the plasma in the cavity and accounting for diffuse and Fresnel specular reflection of the wall, the predicted results show that in contrast to cutting or etching, energy absorbed near the critical radius for a deep welding or drilling cavity is higher for s-polarization than that for p-polarization. On the other hand, absorption for p-polarization is higher than that for s-polarization in a shallow cavity. The critical radius indicating the jump of energy flux absorbed is independent of polarization and optical properties of the workpiece. The use of constant specular reflectivity instead of more elaborate c-polarized Fresnel reflectivities to predict absorption is accurate. A decrease in the wavelength of the laser beam and increase in cavity depth reduce the critical radius and enhance the peak of energy flux absorbed. As the focal distance and spot size decrease, both the critical radius and peak of energy flux absorbed increase. The predicted energy flux absorbed from the Monte Carlo method agrees well with an asymptotic solution.     

Complexity of focal spikes suggests relative epileptogenicity

The EEGs of 39 children with focal or multifocal spikes were subjected to singular value decomposition (SVD) as provided by a commercial software program. We noted that in children with spikes but no clinical seizures the variance accounted for by the first component averaged 91.9%, whereas in children with seizures it was 68.0% (p < .001). The first component accounted for 85.4% in children with single spike foci, for 71.5% in those with multifocal spikes, and for 61.4% (p < 0.002) in those with both focal spikes and generalized spike-wave complexes. Spikes in the frontal and frontopolar areas were the most complex, suggesting that at least in children they tend to be the partial expression of a generalized seizure tendency rather than a result of strictly local pathology.     

Image formation by the crystalline lens and eye of the rainbow trout

The image of a distant unresolved point (point image or PI) and modulation transfer function (MTF) of the eye and lens of the trout were recorded with high spatial (0.3 micron) and dynamic (4096 grey levels) resolution for various entrance aperture sizes and focal positions in monochromatic light, and in broadband light simulating sunlight absorbed by a retinal cone pigment. The PI is irregular, with streaks, wisps and speckle, as a result of lens structural irregularity and diffraction of light scattered within the lens and cornea. Maximum diameter of a diffraction-limited aperture area of the eye is about 0.3 mm. Axially spaced multiple foci are caused by irregular and discontinuous zonal spherical aberration. Lens substance dispersion causes strong longitudinal chromatic aberration, resulting in a broadband PI with concentric coloured haloes. Incident linearly polarized light is slightly depolarized in the PI. The nature of the image is discussed relative to lens and cornea structure, optical modelling and vision. Human subjective entoptic phenomena analogous to those observed objectively in the trout are described.     

缺陷控制对胆甾相液晶材料双稳态性能的影响及其应用

通过弯曲分子的掺杂实现了胆甾相液晶平面态油丝缺陷的调控和焦锥形貌的稳定,研究了各因素对双稳态稳定性的影响,并展示了双稳态的潜在应用。偏光显微镜观察和透过率?电压曲线测试结果表明,弯曲分子的引入可以调控甚至消除平面态的油丝缺陷,实现透过率增加,同时调节焦锥态的形貌,使扇形畴更细小破碎,有利于增强焦锥态的散射和稳定性,实现双稳态效果。这是因为弯曲分子具有很小的弯曲弹性常数,进而对胆甾相液晶的弯曲弹性常数和扭曲弹性常数相对大小进行调节。平面取向层的锚定越强,对双稳态(主要是焦锥态)的稳定越不利,但锚定作用太弱,不利于平面态的完美排列。可以通过取向作用强弱调节、盒厚调整来达到较优的效果。少量聚合物的引入有利于实现双稳态的稳定。最后,基于缺陷调制后的双稳态特性制备了无色和彩色的调光膜,展示了双稳态的潜在应用。      

An evaluation of the biocompatibility of intraocular lenses

BACKGROUND AND OBJECTIVE: The degree of cell adhesion to intraocular lenses (IOLs) was studied through the cell culture system and the morphology of adhering cells was studied using a light electron microscope and a scanning electron microscope. MATERIALS AND METHODS: Human lens epithelial cells were used as materials. The IOL materials were classified into four groups: polymethylmethacrylate (PMMA), heparin surface modified PMMA, surface passivated PMMA, and silicone. RESULTS: PMMA showed greater adhesion than did the other materials. Cells hardly adhered to silicone. Use of a light electron microscope and a scanning electron microscope revealed that cells adhered uniformly to the surface of PMMA and were elongated, but did not adhere uniformly to IOLs of other materials. Only a few cells without the tendency of elongation were noted on the silicone the second day after culture. The 14th day after culture, the surfaces of IOLs, except those of silicone, were covered with cells. CONCLUSION: Such differences in the surface adhesion and morphology of cells adhering to the IOL surface are important in evaluating IOL biocompatibility.     

锌铝镁钢板表面黑点缺陷原因分析与控制

针对厚镀层锌铝镁产品出现的黑点缺陷,使用光学显微镜、激光共聚焦显微镜、扫描电镜、能谱、微区XRD对缺陷进行分析。结果表明,黑点位置富含共晶相,这是由于局部缺少凸出的先析出富锌相、共晶组织对光反射的特点以及镁化合物在空气中的氧化,导致其目视为黑色。使用中性盐雾试验对黑点样品及正常样品进行测试,并对其耐蚀机理进行了分析。结合现场工艺,通过优化冷却制度,增加镀层在凝固时的过冷度,抑制共晶相的局部富集,使该问题得到解决。     

锌铝镁钢板表面黑点缺陷原因分析与控制

针对厚镀层锌铝镁产品出现的黑点缺陷,使用光学显微镜、激光共聚焦显微镜、扫描电镜、能谱、微区XRD对缺陷进行分析。结果表明,黑点位置富含共晶相,这是由于局部缺少凸出的先析出富锌相、共晶组织对光反射的特点以及镁化合物在空气中的氧化,导致其目视为黑色。使用中性盐雾试验对黑点样品及正常样品进行测试,并对其耐蚀机理进行了分析。结合现场工艺,通过优化冷却制度,增加镀层在凝固时的过冷度,抑制共晶相的局部富集,使该问题得到解决。     

Problems in timing of respiration with the nasal thermistor technique

Twelve normal control phakic eyes together with a number of other pseudophakic groups each consisting of 6 eyes were enrolled in this study of spatial and quantitative measurement of glare disabilities in the static visual field (Perimetric Glare Test) using an OCTOPUS 500E automated perimeter with an attached glare source. These groups were a 6 mm no hole lens group, a 6 mm 4 hole lens group, a 5.5 x 6.5 mm 2 hole lens group, a 5.0 x 6.0 mm no hole lens group and a diffractive multifocal group. Glare disabilities in the visual field were minimum in the control group. The 6 mm no hole lens group and the diffractive multifocal group showed no statistical significance compared the control group. Groups with the two types of ovoid lens and the 6 mm 4 hole lens group showed a statistically higher degree and a greater extent of glare disabilities in the static visual field than the control group. Careful selection of appropriate patients to receive implants of small efficient optic IOLs, such as IOLs with positioning holes and ovoid lenses, according to the preoperative pupil size under scotopic or mesopic condition and efficient lens optic size are important in order to reduce hole and edge glare. The diffractive multifocal IOLs group showed a slightly higher degree and a greater extent of glare than the control group and the 6 mm no hole monofocal lens group but the difference was very small and statistically insignificant. Therefore the effects of diffractive microstructure on glare disabilities were considered to be slight and clinically acceptable.     

The clinical picture and electroencephalographic changes in patients with multifocal epilepsy depending on the location of the epileptic foci

As many 116 patients were examined for the clinical course and electroencephalographic changes as well as for the x-ray, CT and NMR-tomography data, on the basis of which different forms of multifocal epilepsy were distinguished: with unilateral epileptic foci (cortical and cortico-subcortical form), bitemporal and with multiple bilateral epileptic foci. The data provided make it possible to differentiate between multifocal epilepsy and generalized epilepsy and to perform surgical treatment using the optimal surgical intervention.     

Independent origin of multiple foci of prostatic intraepithelial neoplasia: comparison with matched foci of prostate carcinoma

BACKGROUND: Prostate carcinoma usually is heterogeneous and multifocal, with diverse clinical and morphologic manifestations. Understanding of the molecular basis for this heterogeneity is limited, particularly for the putative precursor, high grade prostatic intraepithelial neoplasia (PIN). In this study, the authors attempted to determine the genetic relation between multiple foci of PIN and matched foci of carcinoma, and whether they are independent in origin. METHODS: The distribution and prevalence of allelic imbalance at 6 microsatellite polymorphic markers on chromosomes 7q, 8p, 8q, and 18q were examined in 84 microscopically excised PIN foci (mean, 1.6 foci/case) and 95 foci of prostate carcinoma (mean, 1.8 foci/case) from 52 completely embedded, mapped whole mount prostates. RESULTS: PIN contained a lower overall proportion of allelic imbalance than matched prostate carcinoma foci for the 6 polymorphic microsatellite markers (65% vs. 82%), but this difference was not significant. The rate of allelic imbalance in PIN was similar to that in prostate carcinoma at 5 of 6 loci studied; the exception, D18S34 (18q12.2-12.3), had a significantly lower rate of allelic imbalance in PIN than in prostate carcinoma (19% vs. 52%), suggesting that genetic alterations in this chromosomal region may be important in carcinogenesis. Of 22 cases with allelic imbalance in at least 1 focus of PIN and 1 focus of prostate carcinoma, 21 informative cases (95%) showed a similar pattern of allelic imbalance at > or = 1 markers in the matched PIN and prostate carcinoma foci. Significant genetic heterogeneity was observed in both PIN and prostate carcinoma. Allelic imbalance was observed in at least 1 focus in 11 of 25 cases with multiple foci of PIN (44%) and 20 of 25 cases with multiple foci of prostate carcinoma (80%). There was no significant correlation between allelic imbalance and pathologic stage or tumor grade. CONCLUSIONS: Our findings indicate that multiple foci of PIN arise independently within the same prostate. This observation suggests that a field effect underlies prostatic neoplasia. Multiple foci of prostate carcinoma also often arise independently, lending additional support for this hypothesis. The strong genetic similarities between PIN and prostate carcinoma strongly suggest that evolution and clonal expansion of PIN may account for the multifocal etiology of carcinomas.     

Comparison of carbon dioxide and neodymium: yttrium-aluminum-garnet lasers in surgery of the inferior turbinate

At the Department of Otorhinolaryngology-Head and Neck Surgery of the University of Kiel, 533 patients with hyperplastic inferior turbinates were treated between 1987 and 1994 with various carbon dioxide (CO2) and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser techniques. We report on the therapeutic results of both types of laser turbinectomy and compare their long-term results with those of submucosal diathermy. Among the different techniques, we preferred the following approaches. The CO2 laser technique involved the application of a few laser spots (laser energy density 6,100 J/cm2 per lesion) to the head of the turbinate under the operating microscope. In the Nd:YAG laser procedure, diffuse, low-power irradiation (laser energy density < 53 kJ/cm2) of the entire concha was performed under endoscopic control. The CO2 laser procedure involved little bleeding and hardly any pain. It produced a positive effect after only a few days and required no follow-up treatment. The success of Nd:YAG laser treatment, by contrast, only became evident after weeks or months, due to the slow scarring process. Compared to submucosal diathermy, both laser methods produced better long-term results. Two years postoperatively, the overall success rate, as defined by patient satisfaction, was 79.6% for the CO2 laser, 68.3% for the Nd:YAG laser, and 36% for submucosal diathermy.     

Rapidly solidified prealloyed powders by laser spin atomization

A new technique, termed laser spin atomization, for the production of rapidly solidified prealloyed powders is described. The results of experiments involving the production of powders of two alloys, one based on Ni, the other on Ti, are presented. The powders have been characterized using light optical metallography, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Auger elec-tron spectroscopy, and these various observations are described.     

Combined esophageal atresia and duodenal stenosis in polyhydramnios. Ante-, peri- and postpartum management]

Three-dimensional sonography of the mamma with a Voluson annular array transducer (10 MHz) (Kretztechnik, Austria) is a new method applicable in differential diagnosis of mamma foci. 50 patients (19 of them with breast cancer) were thus pre-surgically examined. Both sectional and stereoscopic representations were made use of. The suspected diagnoses and their correspondences with post-surgical findings were compared to the correspondences obtained through 2D-sonography. 3D-sonography produced 4 cases of the incorrectly positive diagnosis breast cancer, 2D-sonography 2 cases of incorrectly negative diagnoses. Other advantages of 3D-sonography over 2D-sonography include: better judgement of the conditional of focal environs (infiltration), existence and form of intracystic structures and of multifocal disease, short duration of examination, possible re-diagnosing of stored data.     

Intensity distribution, modulation transfer function, and the effective dimension of a line-focus x-ray focal spot

The radiant intensity along the anode-cathode dimension of a line-focus x-ray focal spot tends to peak at the center and decrease gradually to zero at the edges. In recognition of this varying intensity, the ICRU has recommended that the anode-cathode dimension of the focal spot be reported as 0.7 times the dimension measured with a pinhole camera. In this paper more objective correction factors are developed. These correction factors are based upon comparison of calculated MTFs of focal spots with Gaussian and cosine intensity distributions with the MTF for focal spots with a uniform intensity distribution.     

Progressive multifocal leukoencephalopathy in AIDS: a clinicopathologic study and review of the literature

We reviewed the clinical, radiographic, and pathologic features of 15 patients with the acquired immune deficiency syndrome (AIDS) and progressive multifocal leukoencephalopathy (PML). Brain tissue from 10 autopsy and 6 biopsy specimens was studied using: in situ hybridization (ISH) for JC virus (JCV), immunohistochemistry for human immunodeficiency virus (HIV) p24 antigen, and electron microscopy. Thirteen patients presented with focal neurologic deficits, while 2 presented with a rapid decline in mental status. PML was commonly the initial opportunistic infection of AIDS and produced hemiparesis, dementia, dysarthria, cerebellar abnormalities, and seizures. Magnetic resonance imaging was more sensitive than computed tomography in detecting lesions, and often showed multifocal areas of PML. CD4+ T-cell counts were uniformly low (mean 84/mm3), except in 1 patient who improved on 3'-azido-3'-deoxythymidine (AZT). PML involved the cerebral hemispheres, brain stem, cerebellum, and cervical spinal cord. The distribution of brain involvement was consistent with hematogenous dissemination of the virus. In 2 brain specimens, multiple HIV-type giant cells were present within the regions involved by PML. When co-infection by HIV and papovavirus was present, PML dominated the pathological picture. ISH for JCV showed virus in the nuclei of oligodendrocytes and astrocytes. Occasionally there was staining for JCV in the cytoplasm of glial cells and in the neuropil, the latter possibly a correlate of papovavirus spread between myelin sheaths, as seen by electron microscopy. ISH demonstrated more extensive foci of PML than did routine light microscopy.