Lasers & photonics
Retinal oximetry images taken using the handheld Corimap Camera.
correct myopia, hyperopia and astigmatism by removing the cornea or using a cutting laser to precisely shape it. LASIK is probably the most popular technique nowadays and it normally requires two types of lasers for the different processes: a femtosecond laser for cutting – because the ultrafast pulses avoid mechanical and thermal damages in the tissue – and an excimer ultraviolet laser to perform the modification of the cornea, without affecting the other parts of the eye.
Capsulotomy and iridotomy treatments are other good examples of photonics in action. Several millions of cataract surgeries are performed worldwide each year, with an important incidence of post-operative secondary cataracts. Nd:YAG laser capsulotomy has been widely used as an effective treatment for posterior capsule opacification (PCO). It avoids complications such as endophthalmitis and vitreous losses and improves visual acuity in patients after the treatment. Although Nd:YAG laser capsulotomy is accepted as a standard treatment for PCO, it can present some complications. In order to overcome them, several new developments have been made to these lasers. The goal is to enable more efficient, accurate and safe treatments with the most versatile platform possible. As an example, the high-quality optics used in the new Capsulo laser, from Lumibird Medical, allow for better visualisation of the structures in the anterior and posterior segments of the eye. This laser also includes a variable height light tower, which offers dual illumination angles of 16° and 7.5° for improved diagnostics and treatment of both segments.
Diagnostic imaging devices Medical diagnosis has also benefitted from the advantages of photonic technologies, particularly those based on imaging. In general, we can call medical imaging a set of techniques and processes to get images of the interior of a body for clinical analysis, medical intervention and visual representation of the function of some organs or tissues. Several emission sources have been used to obtain images of the human body, including those emitting light. We can mention, for example, the photoacoustic imaging technique, in
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which several laser pulses are delivered into a biological tissue where some ultrasonic waves are generated, or the functional near-infrared spectroscopy (fNIRS), an optical brain monitoring technique. Another of these techniques, the Optical Coherence
Tomography (OCT), has revolutionised the clinical practice of ophthalmology. OCT is a high resolution, non-contact advanced optical imaging technique developed for non-invasive cross-sectional imaging of biological systems. OCT can provide 2D and 3D images of the different segments of the eye with micrometre resolution. The structural information is derived from the light backscattered or backreflected at the interfaces between the regions of different optical properties within the object. Besides morphology, OCT reveals and visualises such properties of biological objects as velocity of flow (via Doppler effect), birefringence (via polarisation changes) and tissue extinction. It was initially used to obtain high resolution 3D images of the retina, allowing for the detection of morphological changes in the eye and preventing various eye diseases, including glaucoma and macular degeneration. In recent years, a 3D evaluation of the anterior segment of the eye has also become possible, allowing us to understand the optical quality of the human eye.
There are several versions of OCT, depending on the components used and the configuration of the set-up, but swept-source optical coherence tomography (SS-OCT) has stood out over the rest of the options due its high imaging speed. SS-OCT systems can obtain high-resolution images while reducing the negative effect of patient’s eye movements on scan quality. This performance of SS-OCT is mostly attributable to the laser source characteristics, a wavelength-swept laser. Companies such as CareGlance s.r.l. have been working on new lasers to transform OCT into a real-time, portable technique. They have developed new fast and cost-effective swept sources, granting a 1MHz scan speed together with high coherence and resolution. The high speed is achieved by means of a µs-response time tuneable material, while compactness is granted through an optimised micro- optics cavity assembly.
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Demcon Focal B.V
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