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.

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.

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.

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.

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.

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.

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.

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.

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.

Concepts for nanoscale resolution in fluorescence microscopy.

Spatio-temporal visualization of cellular structures by fluorescence microscopy has become indispensable in biology. However, the resolution of conventional fluorescence microscopy is limited by diffraction to about 180 nm in the focal plane and to about 500 nm along the optic axis. Recently, concepts have emerged that overcome the diffraction resolution barrier fundamentally. Formed on the basis of reversible saturable optical transitions, these concepts might eventually allow us to investigate hitherto inaccessible details within live cells.

A generic camera model and calibration method for conventional, wide-angle, and fish-eye lenses.

Fish-eye lenses are convenient in such applications where a very wide angle of view is needed, but their use for measurement purposes has been limited by the lack of an accurate, generic, and easy-to-use calibration procedure. We hence propose a generic camera model, which is suitable for fish-eye lens cameras as well as for conventional and wide-angle lens cameras, and a calibration method for estimating the parameters of the model. The achieved level of calibration accuracy is comparable to the previously reported state-of-the-art.

[Visual rehabilitation in patients with retinitis pigmentosa]. / Reabilitação visual em pacientes com retinose pigmentária.

PURPOSE: To determine which low-vision aids could be useful to patients with retinitis pigmentosa and also the benefits that the rehabilitation program could provide based on visual acuity and/or daily visual tasks. METHODS: A group of 30 patients with retinitis pigmentosa aged from 7 to 73 years were enrolled in this study. Visual acuity and visual function tests (visual field, full-field electroretinogram) was performed and low-vision aids tested. Information about the use of the remaining vision was obtained. After choosing the best optical or electronic devices and before their prescription, a low-vision training program was carried out. RESULTS: The best corrected visual acuity varied from HM (hand movements) to 20/40 for distance and visual acuity better than 16M to 0.5M for near. 90% of the patients had optical devices prescribed: 13 for near, 9 for distance, 2 electronic devices and 3 filters. Three patients with extremely narrow visual field and very low visual acuity were referred to orientation and mobility. CONCLUSIONS: The low-vision aids were useful for the retinitis pigmentosa patients: telescopes, hand-held magnifiers, stand magnifiers, half-eye base-in prism lenses, electronic devices and illumination control were beneficial to enhance visual acuity and visual efficiency. The prescription of low-vision aids was helpful in daily-life activities and a high level of satisfaction with the implemented visual rehabilitation program was reported.

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.

Biomicroscopic measurement of the optic disc with a high-power positive lens.

PURPOSE: To compare the magnification properties of four different indirect double aspheric fundus examination lenses for clinical disc biometry. METHODS: Experimental study in a model eye. The relationship between the true size of a fundus object and its image was calculated for each fundus lens for an ametropic range between -12.5 and +12.6 D using a slit lamp biomicroscope with adjustable beam length. RESULTS: Equations for determining the correction factor p (degrees per millimeter) were calculated for each fundus lens. The factor can be used in calculations to determine true optic disc size. The total change in magnification of the system from myopia to hyperopia was -21.1% to +24.0% (60-D lens; Volk Opticals, Mentor, OH), -12.9% to +16.2% (Volk super 66 stereo fundus lens), -13.2% to +13.9% (Volk 78-D lens), and -13.3% to +14.0% (Volk super-field NC lens). When the fundus lens position was altered im relation to the model eye by +/-2 mm under myopic conditions, the change in magnification of the system was -4.3% to +5.7% (60-D lens), -4.6% to +6.1% (66 stereo fundus lens), -4.9% to +6.3% (78-D lens), and -5.9% to +7.8% (super-field NC lens). In the hyperopic condition the change was -2.7% to +3.6%, -3.4% to +4.5%, -3.6% to +4.8%, and -4.5% to +6.0%. CONCLUSIONS: The study has shown that the use of a single magnification correction value for each fundus lens may not be appropriate. These findings have important implications for the way in which calculations for determining the true optic disc size and other structures of the posterior pole are performed using indirect biomicroscopy.

Pathology of the corneal endothelium.

Clinical specular microscopy has indicated that human cell healing occurs by spreading, there is a limited healing reserve, and premature cell loss is the equivalent of a "premature aging" that may lead to later decompensation. This instrument has been useful in studying healing and cell damage from surgery, drugs, and special procedures such as intraocular lens insertion. It pointed out extensive cell loss at the time of intraocular lens insertion, and subsequent studies have indicated that at least part of this cell loss may be due to the methacrylate surface of the lens. Laboratory studies suggest that coating that surface can prevent this component of cell loss. The magnitude of benefits to be found from such coating requires further clinical study.

Visolett magnifier. Evaluation and optics.

The Visolett is a glass, nonspectacle magnifier that rests on the paper, producing 1.8X to 2.5X magnification. It is one of the most useful nonspectacle magnifiers, because it is simple to use and diffusely concentrates illumination on its own field, enhancing the magnification. The optics differ from usual hand magnifiers in that the magnification does not increase with the dioptric power.