A modular, open-source, slide-scanning microscope for diagnostic applications in resource-constrained settings.

In this paper we report the development of a cost-effective, modular, open source, and fully automated slide-scanning microscope, composed entirely of easily available off-the-shelf parts, and capable of bright field and fluorescence modes. The automated X-Y stage is composed of two low-cost micrometer stages coupled to stepper motors operated in open-loop mode. The microscope is composed of a low-cost CMOS sensor and low-cost board lenses placed in a 4f configuration. The system has approximately 1 micron resolution, limited by the f/# of available board lenses. The microscope is compact, measuring just 25×25×30 cm, and has an absolute positioning accuracy of ±1 µm in the X and Y directions. A Z-stage enables autofocusing and imaging over large fields of view even on non-planar samples, and custom software enables automatic determination of sample boundaries and image mosaicking. We demonstrate the utility of our device through imaging of fluorescent- and transmission-dye stained blood and fecal smears containing human and animal parasites, as well as several prepared tissue samples. These results demonstrate image quality comparable to high-end commercial microscopes at a cost of less than US$400 for a bright-field system, with an extra US$100 needed for the fluorescence module.

Assessing the Use of Loupes and Lights in Dental Hygiene Educational Programs.

Purpose: The purpose of this study was to explore the use of loupes and lights in dental hygiene programs, to assess why they are being used, and to evaluate at what point in time they are introduced to students within the curriculum.Methods: A 20 question survey was developed and pilot tested. The survey was disseminated electronically to 335 dental hygiene program directors in the United States. Frequency distributions were analyzed to provide an overview of the data and Fisher's Exact Test was used to investigate differences between technical/community college programs and university-based programs.Results: Out of the 335 electronic surveys, 143 were completed for a response rate of 47%. Prevention of musculoskeletal disorders, ergonomics, and enhanced vision for instrumentation remain the top three advantages of using loupes. Ninety-six percent of respondents indicated students use loupes and over 50% of faculty use loupes. Fifty-seven percent of dental hygiene programs encourage students to purchase loupes with a light. Fifty percent of students pay $601-$900 for loupes and 47% pay $300-$600 for a light.Conclusion: Student and faculty use of loupes and lights are increasing in educational programs. Future research should focus on the longitudinal impact of using loupes/lights, the prevention of musculoskeletal disorders, and an investigation of the continued use of loupes in a professional setting post-graduation.

Effectiveness of Air Drying and Magnification Methods for Detecting Initial Caries on Occlusal Surfaces Using Three Different Diagnostic Aids.

Objective-The aim of this study was to assess the effect of magnification and air-drying on detection of carious lesion. Study Design-44 human extracted premolars were selected with sound occlusal surfaces without frank cavitation. The Diagnostic techniques used were Unaided visual examination, Magnifying Loupes (4.2×) and Stereomicroscope (10×, before and after air-drying) and then the teeth were sectioned bucco-lingually and both the surfaces were examined under Stereomicroscope (50×) to assess the presence or absence of carious lesion in the pit and fissures. The scores were compared to obtain Cohen's kappa coefficient (Reproducibility) and subjected to the Friedman Test and Paired t test. Sensitivity, specificity and positive predictive value used to assess accuracy. Results-On Statistical analysis, visual examination before and after air drying had highest specificity but lowest sensitivity compared to different diagnostic techniques. Magnifying loupes after air-drying had highest sensitivity and lowest specificity compared to other diagnostic techniques. Conclusion-Air drying combined with magnifying aids are cost-effective, reliable method for detection of early carious lesion. If used in pediatric clinical practice, any undesirable pain and discomfort to the patient due to invasive procedures and helps in employing preventive measures.

The takeaway Frenzel goggles: a Fresnel-based device.

OBJECTIVE: To develop and evaluate new thin and light glasses for the examination of patients with nystagmus and to compare them with Frenzel goggles. METHODS: First, we designed new examination glasses: a Fresnel-based device with a short focal length that is not as heavy or bulky as Frenzel goggles. Second, visual-fixation suppression of postrotatory nystagmus with Frenzel goggles and the Fresnel-based device, the latter with 2 different magnifications (2- and 4-fold), was compared in 13 healthy subjects. Third, the intensity of the peripheral vestibular spontaneous nystagmus-in 6 patients with acute vestibular neuritis-with the Frenzel goggles and the Fresnel-based device with the 4-fold magnification was compared. Fourth, the visibility and clinical applicability were evaluated. RESULTS: The Fresnel-based device weighs 6 g (dimensions 12 × 8 × 0.3 cm). There was no significant difference in the intensity of postrotatory nystagmus between the Fresnel-based device with 4-fold magnification (37.3 ± 17.9°/s) and the Frenzel goggles (39.0 ± 18.3°/s). There was also no significant difference between the intensity of peripheral vestibular spontaneous nystagmus in the patients with acute vestibular neuritis. The Fresnel-based device can be easily applied. CONCLUSION: For suppression of nystagmus, the new Fresnel-based device or so-called M glasses is not inferior to Frenzel goggles. Doctors can carry it in their pocket, it is inexpensive, and easy to handle and to fix to the patient's nose so that it can be used in daily practice for the bedside examination. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that, in subjects with nystagmus, a Fresnel-based device identifies a similar intensity of nystagmus as that identified by Frenzel goggles.

Low-cost mobile phone microscopy with a reversed mobile phone camera lens.

The increasing capabilities and ubiquity of mobile phones and their associated digital cameras offer the possibility of extending low-cost, portable diagnostic microscopy to underserved and low-resource areas. However, mobile phone microscopes created by adding magnifying optics to the phone's camera module have been unable to make use of the full image sensor due to the specialized design of the embedded camera lens, exacerbating the tradeoff between resolution and field of view inherent to optical systems. This tradeoff is acutely felt for diagnostic applications, where the speed and cost of image-based diagnosis is related to the area of the sample that can be viewed at sufficient resolution. Here we present a simple and low-cost approach to mobile phone microscopy that uses a reversed mobile phone camera lens added to an intact mobile phone to enable high quality imaging over a significantly larger field of view than standard microscopy. We demonstrate use of the reversed lens mobile phone microscope to identify red and white blood cells in blood smears and soil-transmitted helminth eggs in stool samples.

Use of dental loupes among dental trainers and trainees in the UK.

INTRODUCTION: Magnification loupes are used in dentistry where increased visual performance is needed. The interest and use of loupes among dental practitioners and students appears to be growing. Despite this little quantitative data regarding the use of loupes in clinical practice and factors governing their purchase among dental trainers and trainees is available. OBJECTIVE: To determine the extent of use of loupes among dental trainers and trainees in the UK and identify what factors influence their choice of selection. METHOD: A proforma questionnaire was designed to collect the information required and was handed out dental trainers and trainees. RESULTS: Use of loupes is more common among the dental trainers (44%) than trainees (28%). Of the nonusers, increased interest among the trainees (83.6%) and trainers (50%) in purchasing loupes was noted. Price was found to be the most important factor during purchase. The majority of users opted for 2.5×; and a light source was a popular choice. Both users and nonusers in the study group had an affinity towards "through-the-lens" type. No significant variation in back/neck discomfort between the users and nonusers was found. CONCLUSION: Use of loupes among dental trainers and trainees remains low. Reduction in price and provision of information could increase the number of loupe users.

Lens-free imaging for biological applications.

Lens-free (or lensless) imaging is emerging as a cost-effective, compact, and lightweight detection method that can serve numerous biological applications. Lens-free imaging can generate high-resolution images within a field-portable platform, which is ideal for affordable point-of-care devices aiming at resource-limited settings. In this mini-review, we first describe different modes of operation for lens-free imaging and then highlight several recent biological applications of this emerging platform technology.

Low-cost adaptive astigmatism compensator for improvement of eye fundus camera.

In this work we show a conceptually simple and cheap means by which to improve retinal image quality in fundus cameras. We will explain how to build a low-cost variable astigmatism-correcting device with a pair of identical commercial ophthalmic lenses. We have developed and tested a low order aberration compensation device capable of correcting astigmatism prescriptions up to -8.00 D with no significant addition of higher order aberrations. A theoretical description of the device, calibration, and improvement in retinal images without employing any image restoration technique will be shown.

High performance gel imaging with a commercial single lens reflex camera.

A high performance gel imaging system was constructed using a digital single lens reflex camera with epi-illumination to image 19 × 23 cm agarose gels with up to 10,000 DNA bands each. It was found to give equivalent performance to a laser scanner in this high throughput DNA fingerprinting application using the fluorophore SYBR Green(®). The specificity and sensitivity of the imager and scanner were within 1% using the same band identification software. Low and high cost color filters were also compared and it was found that with care, good results could be obtained with inexpensive dyed acrylic filters in combination with more costly dielectric interference filters, but that very poor combinations were also possible. Methods for determining resolution, dynamic range, and optical efficiency for imagers are also proposed to facilitate comparison between systems.

Disposable microscope objective lenses for fluorescence correlation spectroscopy using latex microspheres.

We explore the combination of a latex microsphere with a low NA lens to form a high performance optical system, and enable the detection of single molecules by fluorescence correlation spectroscopy (FCS). Viable FCS experiments at concentrations 1-1000 nM with different objectives costing less than $40 are demonstrated. This offers a simple and low-cost alternative to the conventional complex microscope objectives.

The rise and fall of the jewel microscope, 1824-1837.

To increase the resolution of the microscope Sir David Brewster proposed that lenses should be made from materials of high refractive index. In 1824 Dr C.R. Goring commissioned Andrew Pritchard to make a diamond lens, which was delivered at the end of that year. Pritchard made other jewel lenses and devised a stand for use with them. Inhomogeneities in the gem stones and the improvements in the design of objectives published in 1830 by J.J. Lister, led to the abandonment of jewel lenses for microscopy. The properties of twelve jewel and two fused quartz lenses have been measured and are tabulated.