Micro Components are KEY in the Treatment of Eye-related Illnesses
6/2/16 There are many illnesses that plague the eye. Below are a few examples and how micro-sized components aid in the treatment of these illnesses.
Glaucoma affects many elderly, African Americans, and those with a family history. It is considered the 2nd leading cause of blindness (after cataracts) and 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:
- Trabeculectomy (laser surgery) is most common approach; creates a hole in sclera to allow fluid to drain into the outer cyst
- Conventional surgery can also be used to create a drainage hole in the white part of the eye if laser surgery is unsuccessful
- Implant surgery positions a device to aid the drainage; estimated that several thousand are performed each year in US
- Canaloplasty places a microcatheter into Canal of Schlemm to enlarge the natural drainage channel for healthy eye
A glaucoma drain, commonly known as a shunt, is shown in the above image. 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.
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. Prior to 2007, medicine was not available to treat AMD; in 2007 the market was estimated to represent more than $1.2 billion in sales.
The above image shows an AMD guidance device 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.
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 plugs (See Figure 1.4) 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