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PubMed1991

Adjustable focus telescopes for near vision.

It is important for clinicians to know the equivalent viewing power and corresponding equivalent viewing distance of the adjustable-focus telescopes they prescribe for low vision patients. Formulas are presented here to calculate the equivalent viewing power and distance of these telescopes. The optical effects of adjusting a telescope for near vision are discussed and compared to using a lens cap fitted on the objective to permit focusing on a near target. Commonly prescribed adjustable-focus telescopes of four representative magnifications were evaluated. The results are presented in the form of a nomogram which can be used for determining the equivalent viewing distance of these telescopes based on the front vertex focal distance of the focused device. Other considerations including sources of error and field of view are also addressed.

Eyeglasses↗
PubMed2001

The development of the Ocutech VES-autofocus telescope and a future binocular version.

Conventional optical low-vision devices are hampered by the physical constraints of magnification-shallow depth of field and narrow field of view, and for telescopes, the need to change focus for different distances. These characteristics make low-vision telescopic aids difficult to use, especially at important midrange distances. The Ocutech VES Autofocus bioptic telescope (VES-AF) funded with National Institutes of Health-Small Business Innovation Research and Ontario (Canada) Ministry of Health grants, eliminates the need to manipulate the device to maintain focus. Clinical experience with the VES-AF has shown that autofocus (AF) enhances the acceptance and utilization of telescopic devices. Difficulty ignoring the fellow eye while sighting through the device has been a complaint of users that has undermined device acceptance. Although occlusion is an option to alleviate the diplopia experienced, the development of a binocular version may further enhance the acceptance, adaptation to, and utilization of telescopic devices and may offer wider fields of view as well.

Adult↗
PubMed2003

Telescopic esophageal anastomosis: operative technique, clinical experiences.

The authors reconstructed the continuity of the alimentary tract by performing telescopic esophagogastrostoma in 208 patients who underwent either esophageal resection or total gastrectomy. The substance of the telescopic technique is to invaginate the distal section of any oral tubular organ to the lumen of an aboral tubular one and to fix it there. In case of telescopic esophageal anastomosis a 10-15 mm long esophageal segment is invaginated into the gastric tube or jejunum. A 3-4 mm wide serosal surface of the wall of the distal anastomosing organ straps the esophagus circularly. Ninety-six transthoracic and 12 transhiatal esophagectomies, 19 partial esophageal resections, four esophageal bypasses, and 77 total or extended total gastrectomies were reconstructed using telescopic anastomosis. Undisturbed healing could be observed in 67 patients after esophageal operations and in 46 patients of total gastrectomies. Anastomosis leakage occurred in 12 of 108 patients (11.1%) after cervical esophagogastrostomy. Leakage could be observed in 7 of 44 patients (15.9%) after end to side and in 5 of 64 patients (7.8%) in case of end to end esophago gastrostoma. There were no failures after two cases of cervical esophago-ileocolostoma and 21 of esophagogastrostomas in the thoracic position. All of the 59 intra-abdominal anastomoses healed without complication. Thirteen of 131 patients (9.9%) died after esophageal operations and four of 77 (5.2%) after gastrectomies. There were no mortal complications due to anastomotic leakage. The telescopic anastomosis is a safe alternative method in cases of total gastrectomy or esophageal operation.

Aged↗
PubMed2003

Equal-curvature grazing-incidence x-ray telescopes.

We introduce a new type of x-ray telescope design, an equal-curvature telescope. We simply add a second-order axial sag to the base grazing-incidence cone-cone telescope. The radius of curvature of the sag terms is the same on the primary surface and on the secondary surface. The design is optimized such that the on-axis image spot at the focal plane is minimized. The on-axis rms spot diameter of two telescopes that we studied is less than 0.2 arc sec. The off-axis performance is comparable with that of equivalent Wolter type 1 telescopes.

Journal Article↗
PubMed2005

Cryogenic optical performance of the ASTRO-F SiC telescope.

The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 microm, which is a little worse than our original goal of diffraction-limited performance at 5.0 microm.

Journal Article↗
PubMed2005

Active optics and modified-Rumsey wide-field telescopes: MINITRUST demonstrators with vase- and tulip-form mirrors.

Wide-field astronomy requires the development of larger aperture telescopes. The optical properties of a three-mirror modified-Rumsey design provide significant advantages when compared to other telescope designs: (i) at any wavelength, the design has a flat field and is anastigmatic; (ii) the system is extremely compact, i.e., it is almost four times shorter than a Schmidt. Compared to the equally compact flat-field Ritchey-Chrétien with a doublet-lens corrector, as developed for the Sloan digital sky survey-and which requires the polishing of six optical surfaces-the proposed modified-Rumsey design requires only a two-surface polishing and provides a better imaging quality. All the mirrors are spheroids of the hyperboloid type. Starting from the classical Rumsey design, it is shown that the use of all eight available free parameters allows the simultaneous aspherization of the primary and tertiary mirrors by active optics methods from a single deformable substrate. The continuity conditions between the primary and the tertiary hyperbolizations are achieved by an intermediate narrow ring of constant thickness that is not optically used. After the polishing of a double vase form in a spherical shape, the primary-tertiary hyperbolizations are achieved by in situ stressing. The tulip-form secondary is hyperbolized by stress polishing. Other active optics alternatives are possible for a space telescope. The modified-Rumsey design is of interest for developing large space- and ground-based survey telescopes in UV, visible, or IR ranges, such as currently demonstrated with the construction of identical telescopes MINITRUST-1 and -2, f/5-2 degrees field of view. Double-pass optical tests show diffraction-limited images.

Journal Article↗
PubMed2006

Impact of telescope seeing on laser adaptive optics.

Atmospheric turbulence in the internal light path of a telescope produces noncommon path phase differences that degrade the image quality of adaptive-optics systems employing laser guide stars. The spatial covariance and rms wavefront errors produced by this effect are derived. It is found that the tilt-removed wavefront error ranges from about 12 nm for a representative 30 m telescope to 59 nm for a 100 m telescope of similar optical design. For adaptive-optics systems that aim to derive tip-tilt information from the laser guide stars the error is considerably larger, ranging from 22 nm for the 30 m telescope to 256 nm for the 100 m telescope. This effect can be a significant impediment to the performance of such systems.

Journal Article↗
PubMedDate not supplied

Implant-supported mandibular telescopic prostheses in oral cancer patients: an up to 9-year retrospective study.

PURPOSE: The aim of this retrospective study was to present the results of implant-supported telescopic prostheses in the mandible after removal of malignant tumors. MATERIALS AND METHODS: Between 1991 and 2000, 24 patients with squamous cell carcinoma (16 irradiated, eight nonirradiated) underwent mandibular rehabilitation with implant-supported telescopic prostheses. A total of 111 dental implants were placed. Treatment complications were observed. The cumulative survival rates of the implants and prostheses were evaluated by lifetable analysis. RESULTS: Within a mean follow-up period of 30 months (1 to 108 months), only three implants failed. All other implants are still in function. Of 24 patients, 23 were satisfied with their implant-supported telescopic restorations. Soft tissue, implant, or prosthetic complications occurred very rarely. The cumulative implant survival rate was about 97% and the cumulative prosthesis survival rate was about 95% at 9 years. CONCLUSION: Implants and implant-supported telescopic maxillofacial prostheses can successfully remain in function over a long period. Increased implant and prosthetic complications should not be expected. Therefore, telescopic implant attachments seem to be very useful as a treatment option for prosthetic restoration of the mandible in tumor patients.

Adult↗
PubMedDate not supplied

A randomized control trial of surgical task performance in frontal recess surgery: zero degree versus angled telescopes.

The use of angled telescopes in frontal recess surgery has the theoretical advantage of improved visualization in areas characterized by reduced access such as the frontal recess. However, their use also is accompanied by the disadvantage of increased visuospatial distortion. To examine the surgical error and task performance of angled telescopes when compared with the use of the 0 degree telescope in frontal recess surgery, we carried out a surgical controlled trial on a cadaveric specimen. Ten surgeons performed randomly predetermined surgical tasks on both sides of the frontal recess. The surgical tasks were divided into three components (passing, grasping, and withdrawing) for analysis. Our study revealed significant difficulty passing instruments with the highly angled 70 degrees telescope as implied by the increased passing time ratio (p = 0.000). This was associated with significant risk of passing instruments blindly (p = 0.011), resulting in significant surgical error of hits to the middle turbinate (p = 0.005). This study also showed that use of less-angled telescopes (30 and 45 degrees) in frontal recess surgery does not appear to be associated with these risks.

Cadaver↗
PubMed1987

Optical properties of low vision telescopes.

Angular magnification, resolving power, astigmatism, field of view, eye relief, and light transmittance of 157 low power telescopes comprising 25 models from seven manufacturers were measured. Roof-prism Keplerian telescopes provided about one-half the resolution, 30% lower transmittance, and more objectionable image flare than Galilean designs. The roof-prism was responsible for producing overlapping doubled images that appeared astigmatic-like. The prism further compromised rotational symmetry by deviating the image in a direction along the roof edge. The Keplerian telescopes, however, had about twice the field of view of the Galilean telescopes. Notably, several Keplerian telescope models from different suppliers were found to be optically identical, although they varied 50-100% in price.

Humans↗
PubMed1994

[The telescoping anastomotic technique: experimental efficacy for autogenous microvessel grafting].

An experimental study was performed to investigate the efficacy of the telescoping anastomotic technique for microvessel grafting. The left femoral artery was grafted into a defect in the right femoral artery in 51 rats using the telescoping technique for both the proximal and distal anastomoses. The inferior epigastric vein was grafted in situ in a further 42 rats using the same technique for both the proximal and distal anastomoses as a model of venous grafting for a venous defect. Arterial and venous grafting was performed using the conventional technique in additional rats for control purposes. The time required for anastomosis by the telescoping technique was about half that required by the conventional technique. The patency rate of the 51 arterial grafts was 51/51 (100%), and that of the 42 venous grafts was 40/42 (95.2%). In the histological examinations, the arterial grafts by the telescoping technique showed some stenosis at the site of the anastomosis at 1 week and 3 weeks postoperatively. The venous grafts, however, showed little stenosis at the site of the anastomosis at 1 and 3 weeks postoperatively. The telescoping anastomotic technique was useful for microvessel grafting and effective for saving time.

Anastomosis, Surgical↗
PubMed2002

Vein grafting with telescoping anastomoses for repair of a double-cut artery.

The rat femoral artery was cut in two places, and the telescoping anastomosis technique was used for all vascular repairs in combination with vein grafting, to determine whether the telescoping technique could safely be used more than three times for repair of an artery that has been injured at two places. One cut was repaired with vein grafting, and the other with either a telescoping anastomosis (the triple group) or with a second vein grafting (the quadruple group). The patency rate 3 weeks postoperatively was 86.4% for the triple group, and 90.5% for the quadruple group. Although tension of the repaired vessel was kept low by vein grafting, and deformities of the inserted vessel were carefully minimized, the patency rate was not 100%. It appears that a telescoping anastomosis should not be used more than three times on the same artery in combination with vein grafting.

Anastomosis, Surgical↗
PubMed1979

Telescoping anastomosis of the colon: a comparative study.

The incidence of large-intestinal anastomotic leaks remains unacceptably high. For this reason, we studied the resistance to dehiscence of a telescoping type of anastomosis and compared it with the conventional one-layer, two-layer, and stapled anastomoses in a canine model. These experiments demonstrated that the telescoping anastomosis provided a more resistant suture line during the early postoperative phase and did not cause encroachment of the lumen by the diaphragm, which was consistently produced when an inverting suture line was used. Three days postoperatively the mean bursting pressures of the one-layer, two-layer, and stapled anastomoses were 31 +/- 12, 120 +/- 46, and 52 +/- 21 mm Hg, respectively. The telescoping anastomosis had a mean bursting pressure of 210 +/- 44 mm Hg, which was significantly (P less than 0.01) higher than those of all the other anastomoses tested. However, seven and 14 days after operation, there was no statistically significant difference among the bursting pressures of the various anastomoses. When the different types of anastomoses were examined histologically, it was found that there was considerably more suture-line inflammation, edema, micro-abscess formation, mucosal ulceration and pericolic inflammation of the fat in the one-layer, two-layer, and stapled anastomoses than in the telescoping anastomosis.

Animals↗
PubMed1994

Arterial grafting with the telescoping anastomotic technique for arterial defects.

An arterial graft was taken from the left femoral artery of the rat and grafted into the right femoral artery using the telescoping anastomotic technique at both the proximal and distal anastomoses to compare the patency rate with that of the vein grafts interposed into the arterial defect with the same telescoping technique. The time required for each anastomosis was about 10 minutes and all of the 31 grafts remained patent without application of xylocaine, yielding a higher patency rate than the vein grafts interposed in an arterial defect. The telescoping technique proved to be so dependable that it could be used at least twice in an artery. Inserting one vessel stump into another using the telescoping technique may not itself be responsible for the failure of vein grafts interposed in an arterial defect, but distortion of the slack venous wall of the graft by high arterial blood pressure is.

Anastomosis, Surgical↗
PubMedDate not supplied

Ground-based telescope pointing and tracking optimization using a neural controller.

Neural network models (NN) have emerged as important components for applications of adaptive control theories. Their basic generalization capability, based on acquired knowledge, together with execution rapidity and correlation ability between input stimula, are basic attributes to consider NN as an extremely powerful tool for on-line control of complex systems. By a control system point of view, not only accuracy and speed, but also, in some cases, a high level of adaptation capability is required in order to match all working phases of the whole system during its lifetime. This is particularly remarkable for a new generation ground-based telescope control system. Infact, strong changes in terms of system speed and instantaneous position error tolerance are necessary, especially in case of trajectory disturb induced by wind shake. The classical control scheme adopted in such a system is based on the proportional integral (PI) filter, already applied and implemented on a large amount of new generation telescopes, considered as a standard in this technological environment. In this paper we introduce the concept of a new approach, the neural variable structure proportional integral, (NVSPI), related to the implementation of a standard multi layer perceptron network in new generation ground-based Alt-Az telescope control systems. Its main purpose is to improve adaptive capability of the Variable structure proportional integral model, an already innovative control scheme recently introduced by authors [Proc SPIE (1997)], based on a modified version of classical PI control model, in terms of flexibility and accuracy of the dynamic response range also in presence of wind noise effects. The realization of a powerful well tested and validated telescope model simulation system allowed the possibility to directly compare performances of the two control schemes on simulated tracking trajectories, revealing extremely encouraging results in terms of NVSPI control robustness and reliability.

Models, Theoretical↗
PubMed2003

The effect of three different periodontal pre-treatment procedures on the success of telescopic removable partial dentures.

In this prospective study, 120 teeth consisting of maxillary and mandibular canines and premolars were divided into three groups each containing 40 teeth. The teeth were assigned randomly in quadrants to three different periodontal treatment protocols. The first group was treated with professional prophylaxis only. The second group received additional deep scaling. With the third group, additional surgical periodontal flap surgery and scaling was performed. Both papillary bleeding index (PBI) and probing depth (PD) were evaluated before, during and after treatment. During the subsequent prosthetic treatment phase all teeth were then used as telescope abutments supporting a removable prosthesis. The documentation of the attachment level (AL) was then used as a clinical parameter. One year after the incorporation of telescopic removable partial dentures (RPDs), PD, PBI and AL were again evaluated. The resulting periodontal parameters were compared between the different groups using the general linear model (GLM) repeated measures and the Kruskal-Wallis test for non-parametric variables. Differences within the three treatment groups were determined using the t-test, e.g. the Wilcoxon test for dependent variables (P < 0.05). A significant decrease in inflammatory indices (PBI) was found for all types of periodontal treatment (P < 0.03 for all groups). Additionally, the reduction in PD was significant for all of the three groups (P < 0.001 for all groups). The greatest reduction in PD was observed in the group in which a surgical approach was used. Evaluation of the attachment level after the incorporation of the telescopic RPDs showed that tooth position did not influence the periodontal prognosis and that the use of telescopic RPDs exerted no ascertainable negative influence on the periodontium of the abutment teeth.

Adult↗
PubMed2001

Validation of the scanning -gamma-ray telescope for in vivo dosimetry and boron measurements during BNCT.

Gamma-ray telescope scans of a box phantom with inhomogeneous boron concentrations have proven the feasibility of in vivo measurements of different boron distributions in the head of a patient during boron neutron capture therapy (BNCT). Small structures with enhanced boron concentration can be reconstructed in a head phantom, even if the brain compartment of the phantom is surrounded by a skin layer with a ten times higher boron concentration. The motor-controlled telescope can scan the head/phantom, detecting boron and hydrogen prompt y-rays emitted at neutron capture reactions with a two-dimensional spatial resolution of 14 mm full width at half maximum. For reconstruction of the boron concentrations from the measured y-ray detection rates, a mathematical reconstruction algorithm is derived and discussed. Proper reconstruction requires position-dependent y-ray measurements combined with treatment planning programme calculations of the thermal neutron distribution. In a head phantom, in which the brain and the skull (bulk) were represented using a homogeneous boron distribution of 5.2 +/- 0.5 ppm 10B, surrounded by a skin layer with a ten times higher boron concentration, the bulk concentration was reconstructed to 4.7 +/- 0.3 ppm 10B. Telescope scans along and perpendicular to the beam axis showed the influence of inhomogeneities with a high boron concentration such as skin and a simulated blood vessel, respectively with a low boron concentration such as white matter. The profiles of the boron and hydrogen y-ray detection rates indicate how future patient measurements can be interpreted. In clinical trials, the telescope can then be used to investigate the averaged boron concentration in the bulk of a patient and local enhanced boron concentrations (e.g. in tumour tissue) in order to relate the measured boron dose distributions to the clinical effects of BNCT. Simultaneously, it can serve as quality control of the dosimetry during the irradiation.

Boron↗
PubMed1999

In situ identification of normal visceral tissues using contact telescopic microscopy.

OBJECTIVES: To improve the intraoperative anatomic identification of normal tissues during surgery using histologic-like criteria STUDY DESIGN: A contact telescope was used to identify normal visceral tissues in an animal model using pigs and dogs during routine human surgical procedures. METHODS: Tissues that could be identified grossly were stained topically with methylene blue and then examined with the contact telescope. The histologic appearance of these tissues with the contact telescope was correlated with routine histologic hematoxylin and eosin stains obtained after such tissues were excised. RESULTS: Normal tissues, such as fat, blood vessels, muscle, and parathyroid tissue, can be identified reliably in animals and humans. The contact telescope appears to be able to differentiate between a variety of visceral tissues in the neck and may become useful for practical differentiation between tissues during surgery.

Animals↗