Micro Ophthalmic Ocular Devices and Treatment
8/4/16 The ophthalmology drugs market is classified based on the type of drugs: treatment based drugs, over the counter drugs and ocular anesthetics. Ocular anesthetics are administered by surgeons during surgery. The treatment based drugs are provided based on the diagnosed conditions and are classified as retinal disorder drugs, anti-allergy/inflammatory/infective drugs, dry eye drugs, and anti-glaucoma drugs. Over the counter drugs can be purchased without any need of a prescription. There has been significant growth in this industry due to the increasing incidence and prevalence of eye related disorders such as macular degeneration, presbyopia and diabetic retinopathy. With the introduction of ophthalmic devices equipped with sophisticated technologies using micro components, people are increasingly opting for ophthalmic surgeries to correct their eye related disorders.
The eye is a complex and sensitive organ. There are many structures and targets, located closely together and sometimes, in terms of target for treatment, these structures are conflicting one another in their proximity. Existing in the eye are significant defense mechanisms, such as the tear film and the cornea, that present challenges for medication to enter. Specifically, the vitreous fluid is difficult for injected medication to traverse to reach the posterior of eye.
Anatomy of Human Eye, Photo credit- MasterEyeAssociates.com
Treatment of eye disorders often requires contributions from two or more parts of an inseparable therapeutic triad
• Ophthalmic pharmacology
• Surgery of the visual tract
• Implantable ophthalmic medical devices
Highly innovative specialist companies dominate pharmacological development. These companies define and epitomize the requirement for treatments of these conditions with micro sized and ultra-precision components and assemblies. Anyone who has ever worn corrective contacts and/or been on the bad end of a windy day near an outdoor fire pit, you have probably noticed that the smallest speck in your eye can cause you severe pain. The reasons for intraocular implants being micro-sized then are to provide the eye an extreme level of comfort with the least invasive, yet compliant implants in the human body. The thin and delicate structures of the eye require paper thin and flexible components that are nonetheless strong enough to withstand extreme fluid pressures in and behind the eye. The successful creation of a device that is both paper thin and strong is an engineering challenge that requires the skill and expertise that only micro molding and nano surface specialty companies can understand and implement.
Glaucoma (for example) is principally caused by elevated intraocular pressure within the eye. Micro surgical devices and intraocular implants are used if eye drops are not an effective treatment. Micro components and surgical treatments include:
o Trabeculectomy (laser surgery) is most common approach; creates a hole in sclera to allow fluid to drain into the outer cyst
o Conventional surgery can also be used to create a drainage hole in the white part of the eye if laser surgery is unsuccessful
o Implant surgery positions a device to aid the drainage; estimated that several thousand are performed each year in US
o Canaloplasty places a microcatheter into Canal of Schlemm to enlarge the natural drainage channel for healthy eyes
The above picture shows a glaucoma drain Micro Engineering Solutions worked on, commonly known as a shunt. This shunt is injection molded, spherically shaped with a wedge-shaped radial side action in the tool that creates the drain geometry. At the end of the side action travel is a 250 micron orifice whereby no flash can be tolerated. Shunts are mostly tubular, however this one is 3d shaped and designed for placement in the sclera (side of the eye). It is designed to act like a venturi system which uses the pressure of the eye to push the discharge from glaucoma to behind the eye where it can drain. In addition to the 250 micron entry orifice, there are 4 suture holes of 250 micron diameter (2x a human hair) molded into the top of the implant. These suture holes also must be free and clear of particulate or flash to prevent sutures from cutting during implantable or after surgery.
Another example is Age Related Macular Degeneration (AMD) is the leading cause of permanent impairment of reading ability and loss of fine detail for those over age 65. The macula is the central portion of the retina used for seeing fine detail and can be destroyed in one of two ways beginning at age 60.
In 2004, 1.5% of adults over age 40 experience advanced AMD and 6.1% had intermediate AMD (1.8 and 7.3 million adults, respectively). The dry form is the most common form of AMD but it can become the wet form which is more destructive. In dry AMD light sensitive cells in macula break down. Dry AMD is treated with oral ingestion with a high dose of anti-oxidants and zinc. Wet AMD is characterized by growth of abnormal blood vessels behind the retina. Laser surgery used in a small % of patients to destroy vessels but the treatment also damages the retina. Another treatment approach involves intravenous injection of a photo activated drug into the arm. When exposed to light in the eye the drug is activated and it destroys the new unwanted blood vessels. Injections into the eye to block the growth of abnormal new blood vessels is also available.
The above image shows an AMD guidance device that Micro Engineering Solutions worked on that is used in laser surgery. The spherical radius sits on the cornea and the lens underside must be free of flash, mold parting lines, and surface imperfections. The 300 micron laser hole shuts off on the spherical radius and blending these geometries three-dimensionally in steel to produce the polymer micro injection molded component is very challenging. In this case, material selection was also a key factor in providing the rigidity required to hold the guide in place during laser deployment. USP Class VI materials (they have previously been used in medical products) are necessary and also require OEM testing even if they are shown to be Class VI compliant.
Lastly, Dry Eye is one of the most common reasons for an appointment with an ophthalmologist. Dry Eye condition is defined as an irritation of the eye due to an inability to produce or maintain/retain enough tears on the surface of the eye. It can result in damage to the front surface of the eye and impair vision. The causes vary from specific diseases (such as Sjögren’s syndrome or lacrimal and meibomian gland dysfunction) to other causes including age, gender (women are more susceptible), medications, certain medical conditions, environmental conditions such as exposure to smoke, wind, or dry climates, and other factors such as prolonged use of contact lenses or refractive eye surgeries (LASIK).
Treatment, may require micro components (approximately ¼ the size of a grain of rice) include punctal whereby a plug is surgically placed in both the top and lower eyelid to prevent fluid in the eye from draining, thereby keeping the eye hydrated. Additional treatments use OTC eye drops or prescription lubricants and anti-inflammatories. These medications are extremely costly and if not administered properly (balancing the dropper over the eye and making sure it all gets into the eye) defeats the purpose and wastes consumer and healthcare costs. Much effort is put into micro pumping and micro administering of these fluids with aspirators, implantable pumps, and slow release polymers that release the drug in timed increments.
Punctal plugs placed in drainage channels of the upper and lower eyelids. Photo credit- allaboutvision.com
Many drug delivery devices are now manufactured in non-traditional ways such as silicon wafer technology, MEMS, and ground-up manufacturing methods. These methods are then matched to more traditional top down methods to provide medical and pharmaceutical companies with differentiated and strategic value. These processing techniques are typically developed using “conventional” single micron level positional accuracy using current work holding devices. These methods are inadequate in preventing cross contamination of actives in capillaries and other microscopic microfluidic assemblies.
Non-traditional methods for manufacturing such as nanometer positional accuracy and dust-specked sized injection molded, machined, and assembled components are spawning technological advances in ophthalmic intraocular implants and intraocular drug delivery devices. These new methods combine traditional top down methods and futuristic bottom up methods to provide medical and pharmaceutical device companies with enabling products to treat the likes of glaucoma, macular degeneration, cataracts, dry eye, and even diabetes around the world.
Areas unknown can be explored with micro manufacturing- restoring lost vision, enhancing vision, hydrating eyes in harsh conditions, gaining less invasive ways to cross the elusive blood-retinal barrier, micro-electronics and eyes controlling the brain to control prosthetics, and even controlling motion for paraplegics. Imagine- the technology allowing people to see……people they haven’t seen in years, objects in a room, light in a sky, food on a plate, and to recognize a smile. We are fortunate to be well positioned in micro and nano manufacturing to play a part in enabling these treatments and products that contribute to worldwide health.