Liquid Silicone Rubber (LSR) parts are used extensively in a multitude of fields in the medical industry because it is inert and bio-compatible — plus, it offers excellent compression characteristics. Ophthalmology is one of the medical fields where LSR is widely used and preferred.
What Is Ophthalmology?
Ophthalmology is a branch of medicine associated with the diagnosis and treatment of conditions related to the eye.
The field of ophthalmology encompasses eye examinations, prescribing vision-correcting eyewear or contact lenses, and for more serious conditions, eye surgeries.
Many of the ophthalmological equipment and instruments used in eye treatments and surgeries benefit from components made of liquid silicone rubber.
Most Common Types of Ophthalmological Surgeries
Ophthalmologists handle a wide variety of eye surgeries to maintain the function and health of the eyes. The most common ophthalmological surgeries include the following:
- Cataract surgery: Cataracts develop slowly and cloud the normally clear lens, affecting vision. The likelihood of developing cataracts increases with age. Cataract eye surgery is a procedure in which the ophthalmologist removes the lens of the eye, and in most cases, replaces it with an artificial lens. Cataract surgeries by far are the most common procedure performed by ophthalmic surgeons. There are approximately 10 million cataract operations performed each year around the world. Cataract surgeries are expected to increase even further as the average lifespan increases.
- Vitrectomy surgery: Vitrectomy surgery is a procedure in which the vitreous humor gel in the eye cavity is extracted to create better access to the retina. This type of procedure is used to facilitate various types of repairs, including scar tissue removal and macular hole treatment. Retinal detachments can also be repaired. Approximately 225,000 vitrectomies are performed in the United States annually.
Other common surgeries that ophthalmologists perform include laser eye surgery, glaucoma surgery, corneal surgery, and eye muscle surgery.
Why LSR Is Used for Ophthalmology Applications
In a range of medical fields, including ophthalmology, the use of LSR has risen. LSR has become known as a highly effective material choice for use in equipment and devices. Ophthalmology is no exception. So why is LSR a preferred material choice for ophthalmological applications? Here are just a few characteristics that make it an ideal material choice:
- Resilient: LSR has excellent rebound resilience, meaning it returns most of the kinetic energy that is applied to it. It also has a slower fatigue rate compared to other elastomers, so it doesn’t fail as quickly after physical cycling.
- Dynamic modulation or pumping: LSR is highly sensitive and responsive to physical input. Because of this, it is the chosen material for critical pressure sensing applications, such as those involved in phacoemulsification. Because of its sensitivity and responsiveness, the time between a doctor’s input and the fluid delivery output is minimal.
- Compression set: This means the material returns to its original formation after compression. So, LSR parts with slits and parts designed to seal will return to their original formation. This is especially critical in ophthalmologic applications where it is critical to maintain fluid pressure in the eye to avoid a collapse or rupture that could lead to permanent loss of vision.
- Smooth: Smooth, low–friction surfaces can be achieved with LSR for an effortless flow of fluids or substances.The soft, smooth surfaces are also more comfortable when in contact with the patient Special secondary treatments and specialty grades of silicone are available that provide added low-friction characteristics.
- Flexible and rigid: LSR offers an ideal balance between flexibility and rigidity—it maintains its structure but compresses when desired.
- Biocompatible and pure: With an inorganic backbone, silicone is inert, remains stable in the body, and does not create negative reactions when in contact with organic matter or with close interaction with biological fluids. This is important for parts in pumping applications used to cycle fluid in and out of the eyes.
- Chemical resistance: Silicone resists bacterial growth naturally. Additionally, it won’t break down from sterilization methods. LSR parts can be sterilized with methods including ETO, E-beam, Gamma radiation processes, and Autoclave.
- Compliant: LSR is produced in compliance with stringent FDA requirements for biocompatibility properties. Most medical grades of LSR carry ISO 10993-5,10,11 (Cytotoxicity, Sensitization as per LLNA, Pyrogenicity) and USP Class VI (Systemic Injection, Intracutaneous, Implantation tests) certifications.
Because of its many benefits, Liquid Silicone Rubber is highly conducive for use in a wide array of applications in the ophthalmology field.
Common Ophthalmology Applications for Liquid Silicone Rubber
For procedures such as cataract surgery and vitrectomy, LSR has proved to be a beneficial material for a range of applications. Some applications include:
- Pumping fluids: Fluid management is used during cataract, retinal detachment, and other ophthalmology surgeries. LSR diaphragms are critical components in their function. The diaphragms serve to channel the flow of fluids to and from the eyes. This step is necessary for maintaining pressure in the eyes during surgical procedures.
- Phaco sleeves: The sleeves that cover Phaco needles used in cataract surgery are another application where liquid silicone rubber is used. LSR provides the heat-protective properties as well as a balance between flexibility and rigidity to conform to the patient and maintain the integrity of the fluid channels.
- Actuators: Actuators are components responsible for movement and control in various mechanical applications. In ophthalmology, pneumatically driven actuators made of LSR can be found in retinal cutters used during vitrectomy surgeries to cut the retina wall. LSR’s excellent rebound resilience is advantageous for these types of applications.
- Slit valves: Any application with valves can benefit from the use of silicone. Slit valves or check valves are often made with liquid silicone rubber for vitrectomy and other ophthalmology applications. Silicone naturally reverts back to its original form, maintaining good seals.
- Trocar hubs: Trocars are used in vitrectomies. Liquid silicone rubber is well–suited and universally used for these applications. The trocars are placed within the eye to allow access to the vitreous cavity during vitrectomies and other surgeries.
Whether in surgical devices, in the eye, or in the pumping equipment, LSR offers unique benefits for ophthalmology applications.
Why Cleanrooms Are Essential for Creating Ophthalmology Parts
Because Ophthalmology products will come in close contact with patients’ eyes and eye fluids, they need to meet strict hygienic requirements. Cleanrooms are designed to limit contaminants during manufacturing by using an airlock and air filtration system and requiring operators to be properly dressed.
The use of such cleanrooms allows products to meet strict FDA requirements. This is why SIMTEC Silicone Parts has a class 8 cleanroom that is designed specifically to meet the needs of our customers in the life science industry. Class 8 means the particle concentration is lower than the standard for particles sized 0.5, 1, and 5 microns.
Glossary of Ophthalmological Terms
The following are some terms associated with ophthalmology and ophthalmic surgical procedures:
- Irrigation: The process of providing fluid to the eye.
- Aspiration: This is the process of removing fluid from the eye.
- Phacoemulsification: This is a procedure performed in a type of cataract surgery that involves the eye’s internal lens being emulsified and aspirated from the eye with an ultrasonic handpiece. The aspirated fluids are replaced with a salt solution to preserve the anterior chamber of the eye. Balancing the removed and replaced fluids is critical for maintaining pressure. This balance is accomplished by using a pumping unit with critical pressure readings during occlusion.
- Phaco sleeves: A phaco sleeve is an LSR sleeve that covers the phaco needle used in phacoemulsification. Its function is to protect the lips of the corneal incision from the heat generated by the phaco needle during emulsification. It also directs the infusion of fluid from the base of the phaco needle to the anterior chamber of the eye.
- Vitrectomy cutters: Cutting devices used to cut the retina wall during vitrectomy surgeries. The cutters allow surgeons to get close to tissue without significant vibration or movement and thereby avoid capturing and potentially damaging the tissue. Actuators made of LSR are commonly used in these surgical devices.
- Cannula: This is a small tube inserted into a body cavity or vein to drain fluid, administer medicine, or insert a surgical instrument. It is often made of silicone.
- Trocar: This device is made up of an obturator, a cannula, and a seal. Essentially, a trocar works as a portal for the later placement of other instruments, such as scissors, graspers, staplers, and other tools. It is often a two-shot part made of LSR and polycarbonate.
- Intraocular lens (IOL): An IOL is an artificial replacement lens inserted after cataract surgery. Typically made from Polymethyl methacrylate (PMMA), IOLs are the most common lenses used after cataract surgery, accounting for approximately 79% of the cataract surgery device market.
- Ophthalmic viscoelastic device (OVD): An OVD is a viscous aqueous solution that is used to maintain space in the anterior chamber of the eye during surgery and typically administered with a syringe. This solution is filled into the anterior chamber to help give more clearance for surgical procedures and to keep the cornea away.
Contact SIMTEC for Ophthalmology and Other Medical Parts
If you have hygienic product requirements for ophthalmology applications, SIMTEC can offer years of experience and LSR expertise to provide extraordinary solutions. In addition to our Class 8 cleanroom for strict particle-free requirements, SIMTEC’s customized, highly-automated manufacturing is clean, efficient, and a hands-free process. Our focus is on producing high–quality parts. Our LSR, LSR two-shot, multi-shot, and LSR overmolding technologies have exceptional process stability to deliver consistent and reliable part quality.
At SIMTEC, we prioritize early involvement, working closely with our customers to provide design optimization and pre-production prototyping for design validation manufacturing (DVM), and for clinical trials and testing purposes. Once the design is frozen, we are ready to kick-off high–capacity production molds and high-volume, long-term parts production.
Contact SIMTEC with your next high–volume program and see how our LSR for ophthalmology parts can deliver exceptional results.