Adjustable Lens Research Articles

Development of a repeatedly adjustable intraocular lens

Purpose: To provide a variable-focus intraocular lens (IOL) that is able to adjust repeatedly and reversibly. Setting: University of Missouri-Rolla, Rolla, and Eggleston Adjustable Lens, St. Louis, Missouri, USA. Methods: An adjustable IOL based on a mechanically adjustable design has been developed. Prototypes were fabricated from traditional Perspex ® CQ poly(methyl methacrylate) (PMMA) provided off the shelf by a current IOL manufacturer. The prototypes have undergone proof-of-concept testing per the requirements of National Institutes of Health grant 1 R41 EY13482–01, with specific attention to the feasibility and safety of continuing development of the lens with in vivo trials. The experimental results presented focus on operational force measurements. Results: Prototype lenses were produced consistently. Operational force measurements indicated that use of the mechanical adjustment mechanism is viable for an adjustable IOL and provides repeated adjustments over time. Turning forces exhibited by the prototypes were low enough to suggest that operation of this adjustable IOL will not damage the capsular bag or ciliary body of the eye, a potential concern in using this design. Biocompatibility and optical quality of the prototype lenses are ensured by use of traditional Perspex CQ PMMA. Conclusions: The mechanically adjustable IOL provides a feasible and promising means of confronting postoperative refractive errors and the changing desires of patients. The viability of this IOL design has been proven, and results suggest that operation of the lens is safe enough to pursue in vivo trials. Evaluation of the biocompatibility of the lens architecture as well as the ultimate goal of noninvasive adjustment using this model are reported in a companion article.

Magnetically adjustable intraocular lens

Purpose: To provide a noninvasive, magnetic adjustment mechanism to the repeatedly and reversibly adjustable, variable-focus intraocular lens (IOL). Setting: University of Missouri-Rolla, Rolla, and Eggleston Adjustable Lens, St. Louis, Missouri, USA. Methods: Mechanically adjustable IOLs have been fabricated and tested. Samarium and cobalt rare-earth magnets have been incorporated into the poly(methyl methacrylate) (PMMA) optic of these adjustable lenses. The stability of samarium and cobalt in the PMMA matrix was examined with leaching studies. Operational force testing of the magnetic optics with emphasis on the rotational forces of adjustment was done. Results: Prototype optics incorporating rare-earth magnetic inserts were consistently produced. After 32 days in solution, samarium and cobalt concentration reached a maximum of 5 ppm. Operational force measurements indicate that successful adjustments of this lens can be made using external magnetic fields with rotational torques in excess of 0.6 ounce inch produced. Actual lenses were remotely adjusted using magnetic fields. Conclusions: The magnetically adjustable version of this IOL is a viable and promising means of handling the common issues of postoperative refractive errors without the requirement of additional surgery. The repeatedly adjustable mechanism of this lens also holds promise for the developing eyes of pediatric patients and the changing needs of all patients.

Ophthalmoscopic examination training using virtual reality

Health care professionals perform ophthalmoscopic examinations to detect pathologies of the eye, as well as to evaluate the effects of other diseases, such as high-blood pressure and diabetes. The ophthalmoscopic examination is given using an ophthalmoscope, a hand-held instrument consisting of an adjustable lens and a focused beam of light. The difficulty of the procedure lies in positioning the ophthalmoscope accurately and then correctly identifying the ocular disease symptoms — skills that improve with experience. To improve and accelerate the training of the student, we developed aVirtual Ophthalmoscopic Examination, a three-dimensional real-time computer simulation of the ophthalmoscopic procedure using virtual reality techniques. By navigating and manipulating the virtual ophthalmoscope in the simulation environment, the student learns how to position the instrument properly. Unlike other training aids that use photographic slides to show the full retina, theVirtual Opthalmoscopic Examination programme simulates an accurate view of the retina. By increasing the realism of the training, the transition from the training programme to live examination of patients will become less difficult. The programme was evaluated by graduate nursing students and was shown to be a promising training aid.

Using a Digital Camera to Teach Physically Challenged Students

Kim, a student who cannot lift a camera to see through viewfinder, learned basic photography by using a digital camera. She parked her batterypowered wheelchair in my office door, and asked if I would be willing to modify some assignments to enable her to take my Graphics of Journalism course. This course includes projects that require students to use computers, cameras and other graphic arts tools such as an X-acto knife, a proportion scale, and a linen tester. No problem, I told her. In past, I have modified or substituted assignments to accommodate students with special needs. Kim's physical challenges would not prevent her from a productive semester in my class. Kim enrolled in course following semester. This article describes one way to adapt new technology to classroom. Kim cannot use her hands or arms because she has no muscles that connect her joints. Kim has Arthrogryposis Multiplex Congenita (AMC), which is characterized by a non-hereditary hypomobility of multiple joints due to fibrous ankylosis. The disease affects Kim's fingers, hands, elbows, and shoulders. She relies on her dextrous feet to handle almost anything -- including a pen, keyboard, and computer mouse. In Kim's case, no computer assignments had to be modified. In fact, no assignments were changed. She turned in her designs as computer printouts instead of mounting them on conventional presentation boards. The basic photography project presented a challenge, however. Because Kim could not hold a camera to look through viewfinder and take pictures at same time, she expected a substitute assignment. Resisting this simple alternative, I struggled with what ifs? What if Kim has a photographic eye but never gets a chance to find out? What if she has an innate sense of photographic balance, composition and framing? What if she has ability to a decisive moment like CartierBresson? At first, I had no solution. How could I offer the photographic to this student? An idea came to me while watching a hockey game on television. I remembered that advertised a camcorder with an adjustable lens and a large preview screen, holding it at arm's length close to ice to his son on video. I considered using this video camera. Kim could shoot a full-motion video, review it, capture or grab individual frames, print them, and submit them as photographs. Technically, I had found a solution. But this would have offered Kim experience of a photo editor, not that of a photographer. We needed a still-frame camera with that Wayne Gretzky interface, but with a preview screen instead of a viewfinder. It could be mounted on her wheelchair so Kim could frame photo and click shutter with her toes. Fortunately, Casio had recently released such a camera. I arranged for Kim to use one. For first time in her life, Kim took a picture. With that one assignment, she discovered an interest and talent for photography. She proved to be a natural. Through my experience with Kim, I discovered that an innovative application of new technology in classroom not only accommodates physically challenged students but empowers them to fully participate in learning process. In turn, this experience allows them to discover and develop talents and skills that may lead to career opportunities never-before-imagined. Photographic study After lectures on photography, photo composition, digital imaging, and picture editing, students were instructed to complete a photographic line study. This is a basic photography assignment that requires students to shoot an aesthetically pleasing picture involving a dominant line. A study is a classic assignment in photography because occurrence of a is often considered one of most powerful design elements in photographic composition. …

Some possibilities of nuclear microprobe focusing system improvement

The first part of this paper describes the numerical studies of some long and short optimal lens systems which consist of three magnetic quadrupole lenses suitable for use in a nuclear microprobe taking into account chromatic and geometrical aberrations of the third order. It is shown how the optimum emittance and the sizes of the object slit and the angular collimator of these systems depend on the microprobe resolution. In the second part of the paper the construction of the new precision adjustable magnetic quadrupole lens is described. The lens is fabricated to an accuracy of some microns by means of electro-erosion machine. The results of magnetic lens measurements are shown in the paper. It is shown that the use of this lens as active element of focusing system would increase the possibilities of operating microprobes.

Direct laser patterned deposition

The ability to write a material pattern directly on a substrate without involving lithography is of considerable technological importance. Research efforts have been targeted towards the development of metal microstrips [1-13] and more recently of microconnections made of high-temperature superconductors [14-16]. Two major approaches have been taken, both employing an intense laser beam as the modus operandi. In the first method organometallic/inorganic precursors are dissociated by laser-induced chemical reactions along the narrow scanning path of the focused laser output [1-6, 8-11, 14]. In the second technique, laser-induced forward transfer [7, 12, 13, 15, 16], the illuminated parts of a thin film are selectively separated from its transparent substrate and transferred on to an adjacent substrate by a single laser shot. The present method of patterning (direct laser patterned deposition) does not require chemistry, a specialized environment or a prefabricated thin film. A substrate transparent at the wavelength of the laser light in use is essential to the method. The laser is focused through the substrate on to a polished bulk target in contact with the substrate. Material is ablated off the target by the laser and is deposited on the side of the substrate facing the target. Patterning is achieved by moving the substrate-target combination which is mounted on an x y stage under computer control in a predesigned fashion. The laser beam can also be scanned across the stationary substrate-target assembly by employing a computer-controlled mirror, an alternative which we have demonstrated. Independently, Cook [17] proposed a similar technique in a patent. As seen in Fig. 1, the laser light is directed via a 45 ° mirror through an adjustable focusing lens towards substrate-target combination. The laser light is transmitted through the transparent substrate and ablates material off the target. The substrate and target are either in direct contact or are separated by a spacer about 200/xm thick. The ablated material deposits on to the side of the substrate facing the target. The target is a polished disc of the material to be patterned on the substrate; the target needs no special preparation and can be re-used repeatedly. In order to generate patterns the substrate-target combination is moved on an x y stage under computer control. We employed the fundamental (1064 nm) as well as the frequency-doubled (532 nm) mode of an Nd:YAG laser operated at 30 Hz. For most applications we used the Q-switched mode which is characterized by a pulse width of about 10 ns. For heat-

A horizontal intravital microscope-plus-bone chamber system for observing bone microcirculation

A horizontal intravital microscope has been built which utilizes the telescope optics format with infinity-corrected objectives. The intravital stage accomodates a rabbit into which a tibial bone chamber has been implanted. The chamber is itself an optical component and is considered an integral part of the system. Each animal is observed in supine position with its implanted leg held in an adjustable spring-loaded yoke which aligns the bone chamber in the optical axis. Long working-distance objectives and condensers allow for viewing of the slit-gap tissue in the bone chamber with both transmitted and epi-illumination; the latter being applied for fluorescence studies. A unique feature of the system is a transfer lens holder which can be relocated within the microscope tube. This adjustable lens holder allows for changing of transfer lenses, thereby freeing the investigator to utilize objective lenses with preferred numerical apertures for a given image size.

Sonic autofocus camera having variable sonic beamwidth

A photographic camera having a plurality of interchangeable, adjustable focus lenses and having a focus control system capable of focusing each such lens over a range of subject distances in response to a rangefinder derived signal is provided with a sonic ranging system that includes an ultrasonic, capacitance-type transducer having a multiple segment backplate whose sonic beam angle is automatically correlated to the field-of-view angle of the image forming lens by selecting a particular combination of backplate segments when or as a particular interchangeable lens is attached to the camera body.

Design and operation of a dual laser chromosome sorter.

We describe the design and operation of a dual laser fluorescence activated chromosome sorter that can analyze and sort chromosome suspensions stained with two complementary DNA stains. We used two 18-watt argon-ion lasers to provide maximal excitation of the DNA-specific stains Hoechst 33258 and chromomycin A3. The lasers are focused onto the sample stream by independent optics permitting optimal focusing of any pair of laser wavelengths. We incorporated beam expanders to decrease the energy density on the optics and improve the focal spot uniformity. Adjustable focusing lens holders are used to set the optimal focal spot size. The redesigned sorter separates suspensions of normal human fibroblast chromosomes into 21 fractions and can reliably sort more pure chromosome fractions than was previously possible.

Simple, adjustable lens holder

The construction of a simple, adjustable lens holder is described. This lens holder is unique in that it will firmly hold small lenses without taking up space at the edge of the lens or stopping them down.

An adjustable field shape electrostatic analyzer

An electric analyzer which permits the generation of any required field shape has been designed and constructed at Rensselaer Polytechnic Institute to be used with a broad range magnetic analyzer in the mass spectrometry program. The adjustable field shape electric lens is built using 20 elements in a 90° sector upon which voltages may be applied independently. First-order focusing theory for the generalized electric sector is developed using the principle of least action. The initial calculations involving determination of the potential distribution, the calculation of potentials for analyzer elements resulting in the most accurate field shape, and the studies of ion trajectories through the field of the lens are discussed. The details of the analyzer construction and operation are included as well as the techniques used to directly measure the focusing action of the lens during operation. Several related applications for this analyzer concept using modified designs are also mentioned.

Observation of plant roots in situ

A technique is described which permits the determination of root penetration, distribution, and density with minimal disturbance to the plant. A small diameter tunnel is made in the soil and fitted tightly with a glass or transparent plastic tube. A fiber optics probe is used to observe the arrival of roots at the wall of the tube at various depths and to estimate their distribution and density. The probe consists of a light source and fiber bundle for illumination, a coherent fiber bundle for image transfer to the surface, a right angle viewing attachment at the objective end, and adjustable lenses.

High Voltage Divider for Image Intensifier Tubes

A corona-free voltage divider with adjustable lens voltages was designed which gives excellent protection to the operator from the high voltage. The divider was built in a box made out of lucite sheets, and a grounded panel is provided between the divider and the operator. Corona-free connectors for 50 and 80 kv were also fabricated. Corona problems and their minimization are discussed. (D.L.C.)

An Improved ƒ/10 Sweeping-Image Camera

A rotating-mirror sweeping-image camera with mirror distortion corrector, faster writing speed, and apochromatic relay lens has resolving power greater than that of earlier models. An adjustable cylinder lens corrects astigmatism from mirror surface distortion. The mirror, rotating up to 2000 rps, gives a maximum writing speed of 13 mm/μsec for about 10 μsec. The ƒ/10 lens gives static resolution of 36 lines/mm on film. Time resolution is estimated at about 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> sec.