LIFE SCIENCES AND MEDICAL DEVICES

OCT

Optics Supporting
OPTICAL COHERENCE TOMOGRAPHY (OCT)

Optical coherence tomography (OCT) is a non-invasive, high-resolution optical imaging technology that creates cross-sectional images from interference signals received from an object under investigation and a reference optic. OCT is commonly used in the medical field to obtain real-time, two-dimensional (2D) and three-dimensional (3D) images in-vivo for direct visualization of tissue structures.

OCT allows improved diagnosis of ophthalmic diseases, such as Age-related Macular Degeneration, AMD (a disease of the retina), which causes blurred vision or diabetic retinopathy, by quantitatively characterizing changes in the structure and appearance of retinal tissue. The effectiveness of therapies can also be tracked using OCT by quantifying the retinal thickness and biomarkers to determine if the disease is progressing. OCT can also be adapted for cardiology, where it enables the diagnosis of the likelihood of a heart attack. One of the leading causes for heart attacks is atherosclerosis which occurs when ruptured fatty plaques and calcium build-up inside the lining of the artery wall, blocking blood flow. OCT allows the detection of vulnerable plaques prior to rupture by visualizing plaques in the arterial wall with an image resolution of 5-7 µm to determine the size, shape, and location of the plaque. In both ophthalmology and cardiology, the ability to accurately diagnose degenerative diseases early makes treatments more effective and provides a better understanding of cellular progression and pathways of many incurable diseases.

Edmund Optics supplies a wide range of optics ideal for OCT systems, including plate and cube beamsplitters, broadband dielectric mirrors, lenses, illumination sources and whole Lumedica benchtop OCT Imaging Systems.

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Optical Coherence Tomography - Overview and Typical Beampath

Optical coherence tomography (OCT) is a powerful medical imaging technique which utilizes light to capture high resolution, three dimensional images from optical scatter in biological tissue. The principles are based off of simple interferometry with near infrared light to effectively penetrate the biological medium. There is a tradeoff to depth penetration and resolution that other technologies can address, but OCT is often coupled with these to ensure accuracy and multi model images.

There are a variety of advanced diagnostic techniques used to treat diseases and ailments of the eye. More and more techniques and devices are emerging due to the progression of optical technology, increasing the accuracy and timeliness of which ailments are diagnosed and providing a pathway for understanding and finding cures for incurable diseases.

LASIK

Laser eye surgery intended to correct human vision. LASIK is a refractive surgery to correct myopia and astigmatism by using a laser to reshape the cornea of the eye, therefore improving visual acuity.

Ophthalmology

Branch of medicine that deals with the anatomy, study, and diseases of the eye. The eye is one of the leading indicators for diagnosing a number of serious ailments. Due to the eyes ease of access and high level of transmission, it has become the “gold standard” for non-invasive medical imaging through various means and technologies such as optical coherence tomography (OCT).

Biometrics / Pupil Recognition

Automated biometric identification using mathematical algorithms to identify and properly recognize an individual’s iris/pupil. This form of biometric recognition is very reliable, as a human’s eye pattern is completely unique, stable over long periods of time, and can be distinguished and recognized over a great distance.

Product Spotlight

Aspheric Lenses

Aspheric lenses feature surface profiles that are not spherical or cylindrical, but have a radius of curvature that varies radially from the center of the lens. Their most notable benefit is their ability to correct for spherical aberration and producing high resolution images. Aspheric lenses are used in many techniques including OCT, biometrics, and LASIK surgery.

Comparison of Spherical and Aspheric surface profiles

Figure 1: Comparison of Spherical and Aspheric surface optics

Figure 1: Spherical aberration in a Spherical Lens (left) vs an Aspheric Lens (right)

Figure 2: Spherical aberration in a Spherical Lens (left) vs an Aspheric Lens (right)

Anatomy, benefits, and manufacturing methods
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TECHSPEC^® Aspherized Achromatic Lenses
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TECHSPEC^® Plastic Hybrid Aspheric Lenses
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Achromatic Lenses

Achromatic lenses consist of two optical components cemented together and are designed to limit the effects of chromatic and spherical aberration. They are used in many devices to diagnose conditions of the eye such as Fundus cameras and broadband OCT systems that utilize the full wavelength spectrum.

Figure 3: Polychromatic Imaging using a Plano-Convex Lens versus an Achromatic Lens

Achromats and their Advantages
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TECHSPEC^® YAG-BBAR Coated Achromatic Lenses
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TECHSPEC^® Mounted Achromatic Lens Pairs
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Standard Singlet and Off-the-Shelf-Optics

When in doubt, go standard! Standard or off-the-shelf optics provide numerous advantages for those designing or creating prototypes. Unlike custom optics, standard optics offer lower prices, in-stock availability, short lead times, no yield efficiency issues, and more.

Figure 4 (left): Plano-Convex (PCX) singlet lens, an ideal off the shelf solution for collimating and focusing applications utilising monochromatic illumination

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Designing with Off-the-Shelf Optics
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TECHSPEC^® λ/20 PCX Lenses
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TECHSPEC^® Beam Shaping PCX Cylinder Lenses
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Case Studies

Figure 5: 3nethra, by Forus Health, plays a critical role in eradicating preventable blindness worldwide

Forus Health

Forus Health leveraged EO’s optical design expertise and off-the-shelf components to build 3nethra, an affordable and portable ophthalmic device for diagnosing preventable eye diseases in India. India has a low ratio of ophthalmologists to population, and this easy-to-use device helps identify and prevent cataracts and glaucoma, along with diabetic retinopathy, refractive errors, and cornea problems.

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Ailments of the Eye

Below are common ailments of the eye that are detected by advanced diagnostic technology. These ailments occur for a variety of reasons such as age or blunt trauma, but are more easily detected and treated due to optical advancements within the industry, which provides a means for updating medical technology and equipment for quick, portable, and simplified use.

Diabetic Retinopathy

Damage to the retinaA thin layer that resides at the back of the eye, which contains cells sensitive to light. These cells trigger a nerve impulse that passes from the optic nerve to the brain, forming a visual image that we process as sight. The cells sensitive to light are known as photoreceptors. onset by diabetes, often leads to blindness. Accounts for 12% of all new cases of blindness in the US, and affects approximately 80% of those suffering from diabetes for an extended period.

AMD

Age-related macular degeneration, a medical condition that causes blurred or no vision at the central field of vision. This condition is onset by damage to photoreceptorsA type of neuron found in the retina that converts light into signals that our brain processes as an image. There are two types of photoreceptor cells known as rods and cones, which work in tandem to form the images that we see. in the macula of the retina and while it rarely leads to total blindness, AMD greatly reduces the ability to see objects or people clearly, if at all.

Glaucoma

Eye disease that causes damage to the optic nerveSensory fiber that carries electrical impulses generated by the photoreceptors in the retina to the brain, where they are processed. and vision loss. The loss of vision is slow and gradual, making glaucoma often overlooked and untreated. It is the 2nd leading cause of blindness around the world.

Cataract

A clouding of the lensTransparent, flexible tissue located directly behind the iris and pupil. It helps focus light onto the retina and provides 25-35% of the eye’s focusing power. A lens changes its curved shape to adjust its focus. in the eye resulting in vision loss. Most commonly onset by age, it can also occur via blunt trauma or poor health. Cataracts account for half of the world’s blindness.