Contact lenses are thin, curved pieces of plastic, typically made of polymers like hydrogels or silicone hydrogels, that sit on the surface of the eye to correct vision. Based on decades of clinical observation and regulatory oversight, the direct link between wearing standard, approved contact lenses and developing ocular or systemic cancer is not supported by current scientific evidence. While the eyes are susceptible to several forms of cancer, such as uveal melanoma and eyelid carcinomas, these malignancies have not been epidemiologically connected to the routine use of contact lenses. The prevailing expert consensus points to a lack of evidence for a cancer risk from approved lens materials.
Scientific Consensus on Contact Lenses and Cancer Risk
Regulatory bodies, including the U.S. Food and Drug Administration (FDA), classify contact lenses as medical devices and subject them to rigorous testing for safety and effectiveness. This oversight ensures the materials used are largely biocompatible and inert, minimizing the risk of adverse biological reactions during long-term contact with the corneal surface. Long-term studies tracking the health of contact lens wearers have not established a higher incidence of eye cancer compared to the general population. The absence of a clear signal in large-scale epidemiological data indicates that the device itself is not carcinogenic.
Recent consumer-commissioned testing has introduced public anxiety related to the presence of per- and polyfluoroalkyl substances (PFAS) in many popular soft contact lens brands. PFAS, often called “forever chemicals,” are man-made compounds linked to an increased risk of certain cancers, notably kidney and testicular cancer, in populations exposed to high concentrations. These chemicals are included in some lens formulations as fluoropolymers to enhance technical performance, such as oxygen permeability and surface lubricity.
Testing found organic fluorine, a marker for PFAS, in all 18 brands examined, with concentrations sometimes exceeding 100 parts per million. Experts acknowledge that while the presence of PFAS is confirmed, the specific biological risk from a lens sitting on the eye’s surface, as opposed to ingestion, is currently unquantified. The cornea is avascular and lacks the systemic absorption pathways of the digestive tract, making it difficult to extrapolate cancer risk from water contamination studies to contact lens wear. Therefore, while a chemical linked to cancer is present, a direct cancer risk from approved contact lens use has not been proven.
Examining Contact Lens Materials and UV Protection
Modern soft contact lenses are composed of water-absorbing polymers, primarily hydrogels or the more advanced silicone hydrogels. These materials are designed to be stable and allow oxygen to pass through to the cornea. The inclusion of fluoropolymers, a type of PFAS, is often necessary in silicone hydrogel lenses to increase oxygen transmissibility, or “Dk” value, preventing corneal oxygen deprivation. These materials maintain their structural integrity and do not typically leach harmful substances in quantities that cause a reaction.
A related concern involves ultraviolet (UV) radiation, a known cause of skin and ocular cancers, including basal cell carcinoma of the eyelid and pterygium. Many contact lenses now contain UV-blocking agents to filter out UVA and UVB light, providing a protective layer for the cornea and deeper structures of the eye. Class I UV-blocking lenses are designed to block over 90% of UVA and 99% of UVB radiation.
UV-blocking contact lenses are not a complete substitute for sunglasses and should not be relied upon as the sole source of sun protection. The lens covers only the central part of the eye, leaving surrounding structures exposed. These include the conjunctiva, the limbus (the junction between the cornea and the sclera), and the eyelid skin. These exposed areas are vulnerable to UV-related damage and subsequent cancer risk, necessitating the use of wrap-around sunglasses and wide-brimmed hats for comprehensive protection.
Proven Ocular Health Risks from Contact Lens Misuse
While the cancer risk from contact lenses remains theoretical and unproven, several acute and chronic ocular health risks are well-documented and directly linked to poor hygiene and misuse. One serious complication is microbial keratitis, a sight-threatening corneal infection often caused by bacteria like Pseudomonas aeruginosa or the protozoan Acanthamoeba. Infections typically occur when lenses are exposed to non-sterile water, such as tap water or swimming pools, or when poor hand hygiene introduces pathogens to the lens surface.
Acanthamoeba keratitis is devastating and strongly associated with rinsing lenses with tap water, as the organism is ubiquitous in freshwater sources. The lens can create minor trauma to the corneal epithelium during insertion and removal, providing an entry point for the microbe. Furthermore, the lens case can harbor a protective biofilm where the organisms thrive.
Corneal Neovascularization
Corneal neovascularization is a physical response to chronic oxygen deprivation (hypoxia) resulting from overwearing lenses, particularly while sleeping. In this condition, the cornea, which is normally avascular, attempts to compensate for the lack of oxygen by growing new blood vessels from the limbus into the clear tissue. These new, fragile vessels compromise the transparency of the cornea and can lead to permanent vision loss if the overwearing behavior is not stopped.
Giant Papillary Conjunctivitis (GPC)
Giant Papillary Conjunctivitis (GPC) is a chronic inflammatory reaction characterized by the formation of dome-shaped bumps, or papillae, on the inner surface of the upper eyelid. GPC is caused by the mechanical friction of the contact lens edge and the accumulation of protein and lipid deposits on the lens surface. These deposits irritate the tarsal conjunctiva with every blink.
Safe contact lens wear requires strict adherence to hygiene protocols. These protocols include:
- Washing hands before handling lenses.
- Using only fresh, recommended solution for cleaning and storage.
- Never exposing lenses to water.
Following the replacement schedule prescribed by an eye care professional is paramount to prevent the accumulation of deposits that contribute to GPC and increase the likelihood of infection. The true risks of contact lens wear are the preventable infections and inflammatory conditions that arise from consistent misuse.