A minimally invasive lens-free computational microendoscope.

Ultra-miniaturized microendoscopes are vital for numerous biomedical applications. Such minimally invasive imagers allow for navigation into hard-to-reach regions and observation of deep brain activity in freely moving animals. Conventional solutions use distal microlenses. However, as lenses become smaller and less invasive, they develop greater aberrations and restricted fields of view. In addition, most of the imagers capable of variable focusing require mechanical actuation of the lens, increasing the distal complexity and weight. Here, we demonstrate a distal lens-free approach to microendoscopy enabled by computational image recovery. Our approach is entirely actuation free and uses a single pseudorandom spatial mask at the distal end of a multicore fiber. Experimentally, this lensless approach increases the space-bandwidth product, i.e., field of view divided by resolution, by threefold over a best-case lens-based system. In addition, the microendoscope demonstrates color resolved imaging and refocusing to 11 distinct depth planes from a single camera frame without any actuated parts.

Using motion capture technology to measure the effects of magnification loupes on dental operator posture: A pilot study.

BACKGROUND: Motion analysis has great potential for quantitatively evaluating dental operator posture and the impact of interventions such as magnification loupes on posture and subsequent development of musculoskeletal disorders. OBJECTIVE: This study sought to determine the feasibility of motion capture technology for measurement of dental operator posture and examine the impact that different styles of magnification loupes had on dental operator posture. METHODS: Forward and lateral head flexion were measured for two different operators while completing a periodontal probing procedure. Each was measured while wearing magnification loupes (flip up-FL and through the lens-TTL) and basic safety lenses. RESULTS: Operators both exhibited reduced forward flexion range of motion (ROM) when using loupes (TTL or FL) compared to a baseline lens (BL). In contrast to forward flexion, no consistent trends were observed for lateral flexion between subjects. CONCLUSIONS: The researchers can report that it is possible to measure dental operator posture using motion capture technology. More study is needed to determine which type of magnification loupes (FL or TTL) are superior in improving dental operator posture. Some evidence was found supporting that the quality of operator posture may more likely be related to the use of magnification loupes, rather than the specific type of lenses worn.

Laparoscopic lens fogging: solving a common surgical problem in standard and robotic laparoscopes via a scientific model.

BACKGROUND: Laparoscopic lens fogging (LLF) hampers vision and impedes operative efficiency. Attempts to reduce LLF have led to the development of various anti-fogging fluids and warming devices. Limited literature exists directly comparing these techniques. We constructed a model peritoneum to simulate LLF and to compare the efficacy of various anti-fogging techniques. MATERIALS AND METHODS: Intraperitoneal space was simulated using a suction bag suspended within an 8 L container of water. LLF was induced by varying the temperature and humidity within the model peritoneum. Various anti-fogging techniques were assessed including scope warmers, FREDTM, ResoclearTM, chlorhexidine, betadine and immersion in heated saline. These products were trialled with and without the use of a disposable scope warmer. Vision scores were evaluated by the same investigator for all tests and rated according to a predetermined scale. Fogging was assessed for each product or technique 30 times and a mean vision rating was recorded. RESULTS: All products tested imparted some benefit, but FREDTM performed better than all other techniques. Betadine and ResoclearTM performed no better than the use of a scope warmer alone. Immersion in saline prior to insertion resulted in decreased vision ratings. The robotic scope did not result in LLF within the model. CONCLUSIONS: In standard laparoscopes, the most superior preventative measure was FREDTM utilised on a pre-warmed scope. Despite improvements in LLF with other products FREDTM was better than all other techniques. The robotic laparoscope performed superiorly regarding LLF compared to standard laparoscope.

Testing feasibility of an accurate microscopic assessment of macrovesicular steatosis in liver allograft biopsies by smartphone add-on lenses.

Light microscopy is an essential tool in histological examination of tissue samples. However, the required equipment for a correct and rapid diagnosis is sometimes unavailable. Smartphones and mobile phone networks are widespread, and could be used for diagnostic imaging and telemedicine. Macrovesicular steatosis (MS) is a major risk factor for liver graft failure, and is only assessable by microscopic examination of a frozen tissue section. The aim of this study was to compare the microscopic assessment of MS in liver allograft biopsies by a smartphone with eyepiece adaptor (BLIPS device) to standard light microscopy. Forty liver graft biopsies were evaluated in transmitted light, using an Iphone 5s and 4 different mini-objective, add-on lenses. A significant correlation was reported between the two different approaches for graft MS assessment (Spearman's correlation coefficient: rs = 0.946; p < .001). Smartphone with eyepiece adaptor had similar discriminatory power to identify MS in liver grafts than standard light microscopy. Based on these findings, a smartphone integrated with a low-cost eyepiece adaptor can achieve adequate accuracy in the assessment of MS in liver graft, and could be used as an alternative to standard light microscope when unavailable.

Prospective, randomized comparison of the use of FloShield Air System® versus the reference technique (water + povidone-iodine solution) during gynecologic endoscopic surgery to evaluate the operative lens vision quality.

BACKGROUND: The FloShield Air System® is a new device for laparoscopic surgery that utilizes a continuous dry CO2 gas flow over the scope to defog the lens and protect it from condensation, debris and smoke. We set out to compare the performance and efficiency of the device in terms of operative lens vision quality (OLVQ) with the reference technique (water + povidone-iodine (PVI) solution) during gynecologic laparoscopic surgery. MATERIALS AND METHODS: We conducted a single-center randomized prospective study between March and June 2016 (Trials Database Registration NCT02702531) including 53 patients undergoing gynecologic laparoscopic surgery with water + PVI solution and 51 patients who underwent surgical procedures with the FloShield Air System. The primary outcome measure was the number of laparoscope removals during surgery. Secondary outcome measures were the time to clean, assessment of the quality of vision, the correlation between the laparoscopic surgical complexity and outcomes, and cost effectiveness. RESULTS: Overall, the mean patient age was 43.2 years (range 22-86) and body mass index 24.8 (range 16.8-42.7). The mean number of endoscope removals during surgery was 7.0 (range 0-37) in the water + PVI solution arm and 2.8 (range 0-12) in the FloShield Air System® arm. The number of removals was significantly lower in the FloShield arm (p < 0.001). No difference in time to clean, quality of vision, level of laparoscopic procedure complexity, or cost was observed between the groups. CONSLUSIONS: The FloShield Air System® resulted in fewer laparoscopic lens removals than the water + PVI solution solution, but that there was no difference in quality of vision, cleaning time or cost, especially for the more complex surgery.

Use of Magnifying Loupes among Dental Professionals.

AIM: The study aims to determine the perspective of dental professionals towards magnifying loupes and the selection criteria used while purchasing them. MATERIALS AND METHODS: In this regard, a close-ended questionnaire was structured and distributed among 111 dental professionals. The questionnaire was designed to obtain information regarding the usage of magnifying loupes in dental practices and procedures, limiting factors, and selection criteria for purchasing. The results obtained from this study were statistically analyzed with the help of SPSS. RESULTS: The findings illustrated that most respondents considered the use of magnifying loupes beneficial in dental practices. Also, 20.7% of them preferred "Through-the-Lens" magnifying loupes over "Flip-up" ones. Furthermore, many of the respondents considered that price, magnification, and resolution are the main factors in terms of selection criteria. CONCLUSION: Although, there is an immense growth seen in the usage of magnifying loupes in dentistry; still there is a need to increase the awareness of the dental professionals regarding the positive outcomes of magnification aids in dentistry. CLINICAL SIGNIFICANCE: The study will help enlightening clinicians regarding the selection criteria while purchasing magnifying loupes for dental practices.

Disposable optics for microscopy diagnostics.

The point-of-care testing (POCT) is having increasing role on modern health care systems due to a possibility to perform tests for patients conveniently and immediately. POCT includes lot of disposable devices because of the environment they are often used. For a disposable system to be reasonably utilized, it needs to be high in quality but low in price. Optics based POCT systems are interesting approach to be developed, and here we describe a low-cost fabrication process for microlens arrays for microscopy. Lens arrays having average lens diameter of 222 µm with 300 µm lens pitch were fabricated. The lenses were characterized to have standard deviation of 0.06 µm in height and 4.61 µm in diameter. The resolution limit of 3.9µm is demonstrated with real images, and the images were compared with ones made with glass and polycarbonate lens arrays. The image quality is at the same level than with the glass lenses and the manufacturing costs are very low, thus making them suitable for POCT applications.

¿Sirve para algo la lente de Goldman en el glaucoma por cierre angular? / Is the Goldman lens any good in angle-closure glaucoma?

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A planar-dimensions machine vision measurement method based on lens distortion correction.

Lens distortion practically presents in a real optical imaging system causing nonuniform geometric distortion in the images and gives rise to additional errors in the vision measurement. In this paper, a planar-dimensions vision measurement method is proposed by improving camera calibration, in which the lens distortion is corrected on the pixel plane of image. The method can be divided into three steps: firstly, the feature points, only in the small central region of the image, are used to get a more accurate perspective projection model; secondly, rather than defining a uniform model, the smoothing spline function is used to describe the lens distortion in the measurement region of image, and two correction functions can be obtained by fitting two deviation surfaces; finally, a measurement method for planar dimensions is proposed, in which accurate magnification factor of imaging system can be obtained by using the correction functions. The effectiveness of the method is demonstrated by applying the proposed method to the test of measuring shaft diameter. Experimental data prove that the accurate planar-dimensions measurements can be performed using the proposed method even if images are deformed by lens distortion.

New application of liquid crystal lens of active polarized filter for micro camera.

Liquid-crystal (LC) lens with low-voltage (3.5V) driving is reported with the experimental results of lens power, wavefront aberration, storage test and also the imaging test. Optical quality can be estimated by interference pattern under two polarizer plates set with the crossed Nichol position, and the optical quality is certified by the measurement of wavefront aberration. Durable stability of over 1000 hours under continuous driving in high temperature (85°C) environment is also verified and obtained less-damaged interference patterns. Finally a new application of active polarized filter for micro camera with focus control function is reported with sufficient quality of images.

Ballistic impact resistance of selected organic ophthalmic lenses.

PURPOSE: The aim was to assess the impact resistance of coated and uncoated mid-index spectacle lens materials using the ballistic impact test. METHODS: Nominally plano lenses of each material in three thicknesses were obtained. The lenses were flat edged to a 50 mm diameter. Each lens was impacted by a 6.35 mm steel ball. Impact velocities were selected using the Zippy Estimation by Sequential Testing protocol to determine the threshold fracture impact velocity. RESULTS: Threshold fracture impact velocity generally increased with thickness; however, there was a wide variation in performance among the various lens materials at each thickness. In all but two instances, the differences in impact velocity at each thickness of lens material were significant. Comparison of the data for CR39 and Hoya Phoenix with the results of earlier studies showed that the lens mounting is a significant factor. The fracture velocities found in the present study were significantly lower than the fracture velocities found when the lens edge is restrained in the mounting. A scratch resistant coating reduced the impact resistance of CR39. The effect of the antireflection coating on the fracture velocity depended on the nature of the base scratch-resistant coating. CONCLUSIONS: Mid-index lens materials of the same thickness show widely varying levels of impact resistance under the ballistic test. Impact resistance increases non-linearly with centre thickness. The lens mounting might affect the results of the ballistic impact test. The presence of 'cushion coatings' might enhance impact resistance.

Guidelines for standard photography in gross and clinical anatomy.

Photography has a widespread usage in medicine and anatomy. In this review, authors focused on the usage of photography in gross and clinical anatomy. Photography in gross and clinical anatomy is not only essential for accurate documentation of morphological findings but also important in sharing knowledge and experience. Photographs of cadavers are supposed to demonstrate the required information clearly. Thus, photographs should be taken with certain techniques in order to obtain high quality and standardization. Camera, lens, lighting, background, and certain photographic techniques are among the factors to achieve precise images. A set of suggested guidelines for accomplishing these standards are given for anatomists.

Prescription compliance in ophthalmic lenses.

PURPOSE: Tolerances required for ophthalmic lenses are set down in national and international standards. It appears that the compliance of manufactured lenses has not been reported previously. Assembling a statistical quantity of lenses of a single prescription is usually an expensive process. It was, secondary to a lens impact study, possible to assemble a large number of plano lenses. In the assessment of the fracture velocity of lenses approximately 20 plano lenses of each material and thickness are required. Prior to using lenses for the impact study, they were checked for prescription. The results of the prescription measurements are reported here and the results of the impact study are reported in a separate paper. METHODS: Using an automated focimeter, 679 plano lenses in stock thickness, typical occupational eye protector thickness and up to 3.5 mm thick were measured. There were 21 combinations of material/thickness/coating from seven suppliers. The power was evaluated against Australian Standard 2228.1-1992, as the lenses were supplied in Australia. The permitted tolerances are ±0.09 D sphere and ±0.06 D cylinder. RESULTS: When assessed for material/thickness/coating combination, failure rates varied from <0.0001 per cent to 77.5 per cent (with a further 17.3 per cent classified as borderline, because they were within the uncertainty of measurement of the required limit). Grouped by supplier, the failure rates ranged from <0.0001 per cent to 7.6 per cent (with a further 12.3 per cent borderline). To improve understanding of the result, it may be easier to quote the figures without considering uncertainties. When assessed by supplier, the failure rate varies from <0.0001 per cent to 12.6 per cent. CONCLUSIONS: Compliance of plano lenses should be among the easiest of tasks for a laboratory. While we know of no defined or required acceptance rates for prescription lenses, a failure rate for a laboratory of 12.6 per cent, which includes a failure rate of 88 per cent in 2.8 mm thick refractive index = 1.53 hard coated lenses (n = 20) cannot be considered satisfactory and is a strong indication of a failure to check lenses before they leave the laboratory.

Guidelines for 1D-periodic surface microstructures for antireflective lenses.

Antireflective properties of one-dimensional periodically microstructured lens surfaces (refractive index 1.5) are studied with the Green's function surface integral equation method, and design guidelines are obtained. Special attention is given to the requirement of having practically all incident light transmitted in the fundamental transmission diffraction order. The effect of the presence of higher transmission diffraction orders is studied to determine if such more easily fabricated structures will be useful. The decrease of optimum fill factor of a periodic array of subwavelength ridges with structure period is explained as a waveguiding effect. Near-fields are calculated illustrating standing-wave interference and waveguiding effects for ridge structures, and adiabatic field transformation for tapered structures, including evanescent near-fields in in- and out-coupling regions. The antireflective properties of tapered geometries are considered for a wide range of angles of light incidence. It is found that while the reflection can be very small this rarely implies high transmission into the fundamental transmission diffraction order when higher-order transmission diffraction orders exist. This leads to the guideline that for visible and normally incident light the surface structure period should not be larger than ~300 nm, and a smaller period is needed in the case of oblique light incidence.

Sunglasses, the European directive and the European standard.

PURPOSE: The Optics and Radiometry Laboratory (ORLAB) provides a testing service for the Australian sunglass industry to assist its compliance with the mandatory Consumer Product Safety Standard. In doing so, a number of sunglasses carrying the CE mark (in effect a claim of compliance with the European Union Personal Protective Equipment Directive) have been tested. Since there is no mandatory testing in Europe (the sunglass industry is deemed self regulating), evaluating their performance will give an insight into compliance with the Directive. METHODS: Consecutive submissions to ORLAB over a period of 18 months were examined for CE marked sunglasses. The results for 646 CE marked pairs of sunglasses tested during 2003 and first half 2004 were examined and evaluated for compliance with EN 1836 (the European sunglass standard) on the basis of refractive power, prismatic power, transmittance (visible, UV and coloration) and polarization. RESULTS: A total of 17.3% failed EN 1836 and 3.3% were borderline (i.e. within our uncertainties of measurement of the requirement). The failures comprised: 0.9% lens defect; 12.5% polarization alignment error; 2.7% excessive vertical prism; 22.3% excessive horizontal prism; 27.7% excessive spherical power; 14.3% excessive cylindrical power; 1.8% excessive UV transmittance; and 23.2% transmittance difference between lenses (always gradient tints). CONCLUSION: With up to 20% non-compliance, self regulation is not working particularly well in providing the public with complying sunglasses.

Minimal movement zoom lens.

We make a novel telescope design using a pair of Alvarez lenses. Previous examples using these types of lenses were single elements used just to provide a change in power. Consequently, the location of the object and/or image plane must move. In this effort, we combine two elements to form a telescope. In this manner, we can fix the location of the object and image plane and simply change magnification. We describe the shapes of the Alvarez lenses used, as well as the advantages, the disadvantages, and the differences between a telescope using Alvarez lenses and a traditional telescope.

Proper care and cleaning of the microscope.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Newly designed ergonomic surgical binocular telescope with angulated optic axis.

OBJECTIVE: Magnification by surgical loupes has the distinct merits of agility and nimbleness in observation, a wide stereo base effectuating superior depth sensation, and light augmentation by an objective lens that is larger than the pupil. However, continuous use of these loupes causes neck strain for surgeons as a result of flexion posture and fatigue. To minimize the strain and fatigue and maximize the advantages and performance of binocular telescopes, we have developed a novel optical design. METHODS: To allow observation of the operative field with the surgeon's neck and eye in a straight position, the light path of the telescopes was angulated downward with roof prisms. For maximum image quality, Keplerian real-image optics were adopted. RESULTS: The optics, finishing of the lens, and assembly were perfected through practical trials of more than 500 procedures over a period of 3 years. CONCLUSION: The new ergonomically designed optics provide excellent image quality comparable to standing microscopes in the low to medium range of magnification, while effectively reducing the neck flexion of surgeons working in the operative field below and relieving the surgeon's fatigue during hours of continuous use.

Calibrating lenses for standard scales of reproduction with digital SLR cameras.

This paper is an update of previous work undertaken by one of the authors (SY) that outlined a method for establishing standard scales of reproduction with digital SLR cameras for clinical photography. Recent experience in the authors' department has raised some issues with using the published formulae for calculating subject and working distances to achieve accurate magnifications. The authors explain a more pragmatic approach to calibrating lenses used on a range of Nikon digital SLR cameras.

Characterization of microscope objective lenses from 1,400 to 1,650 nm to evaluate performance for long-wavelength nonlinear microscopy applications.

We have demonstrated a simple method for characterization of objective lens performance at longer wavelengths for 3PLSM and THG imaging. We investigated a range of air and oil-immersion objective lenses across a wavelength range of 1,400-1,650 nm using a synchronously pumped optical parametric oscillator laser source. In the first instance, we investigated the percentage light transmission across this spectral range. Second, we used a simple second harmonic autocorrelation pulse measurement technique to study the dispersion properties of these lenses at the range of input wavelengths. For the objective lenses investigated, we observed pulse broadening on the order of around 4%-7% for air immersion lenses and 9%-12% for oil immersion lenses. Even for the greater dispersion incurred by the application of the oil immersion lenses, these objectives are suitable for longer wavelength application in conjunction with a suitable light source. The same techniques could easily be applied for a larger range of objective lenses and adapted for alternative spectral windows and pulse durations.