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Fresnel lenses are still in operation today. According to the US Lighthouse Society, more than 75 Fresnel lenses are in use in American lighthouses, and businesses such as Dan Spinella’s Artworks Florida craft replicas that capture the beauty — and functionality — of the 19th-century breakthrough.

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Eye diseases such as age-related macular degeneration, diabetic retinopathy, macular edema, and glaucoma can be diagnosed and monitored through the use of the OCT. In addition, the OCT can detect eye conditions such as macular holes, epi-retinal membranes, and retinal detachments.

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It is important to take the OCT if your doctor requests for it. Many eye diseases and conditions do not have any symptoms. By the time the symptoms present themselves, it may already be too late and lost vision cannot be recovered.

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The most important part of a lighthouse might be one of the beautiful tools hidden inside of it: the Fresnel lens, a breakthrough that changed seafaring and saved lives.

As the above video shows, these lenses satisfied a need for lighthouses that could shine farther and through dense layers of fog. The Fresnel lens, invented by Augustin-Jean Fresnel, helped do that by capturing all the light coming from a lamp, then magnifying and steering it in one direction. Suddenly, lighthouses became more useful and shipwrecks diminished.

The Optical Coherence Tomography (OCT) is the most current and precise technology that is used for diagnostic imaging of the eye. It is similar to an MRI or ultrasound but it is even more precise, with sub-micrometer resolution. The OCT uses non-invasive lasers that are capable of producing cross-sectional and three-dimensional images of the retina.  By taking thousands of scans per second, the OCT ensures high resolution and accuracy for imaging different states of disease in the retina.

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Figure 1. shows a cross-section of the foveal region of the retina, which is where our central vision is located. The image also shows the ten layers of the retina. Figure 2. shows a cross-section of the optic nerve head, which is where nerve impulses carrying visual information are sent to the brain. It is crucial to maintain the health of the retina and the optic nerve as they are both mandatory for sight.

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