Contact lenses are classified as medical devices, requiring professional fitting and ongoing oversight to maintain ocular health. While they offer a popular alternative to eyeglasses, not every individual is a suitable candidate for lens wear. Various factors, ranging from the structural condition of the eye to underlying systemic health issues, can make wearing contacts unsafe, impractical, or impossible. Determining suitability relies on a comprehensive eye examination and a discussion of a person’s health and daily routine.
Chronic Ocular Conditions
The most frequent contraindication to contact lens wear stems from the eye’s inability to maintain a stable, healthy surface. Severe Dry Eye Syndrome (DED) is a primary barrier, as the contact lens sits directly on the cornea and requires a functional tear film for lubrication and oxygen exchange. In DED, inadequate volume or poor quality of tears causes the lens to adhere to the cornea, leading to irritation, abrasions, and a heightened risk of infection.
Chronic inflammatory conditions also pose a considerable risk to the eye’s ecosystem, making lens introduction dangerous. Recurrent microbial keratitis or chronic blepharitis can lead to a constant presence of debris and harmful bacteria. Wearing a contact lens traps these microbes against the cornea, dramatically increasing the chance of a severe, vision-impairing ulcer.
Structural irregularities of the cornea may also prevent a successful fitting. Advanced corneal ectasias, such as severe keratoconus, cause the cornea to thin and bulge into an irregular cone shape, making it impossible for a standard lens to sit correctly. Although custom-designed lenses like scleral lenses can vault over the irregular shape, in the most severe or rapidly progressing cases, a stable fit or comfortable wear cannot be achieved. A persistent, severe form of allergic conjunctivitis, particularly giant papillary conjunctivitis, can also cause the inner eyelid to develop large, irritating bumps that make the friction of a lens intolerable.
Systemic Health and Immune Factors
Beyond local eye issues, body-wide health problems can fundamentally alter the ocular surface, making it intolerant of contact lenses. Autoimmune diseases, such as Sjögren’s syndrome or rheumatoid arthritis, can severely damage the lacrimal and accessory tear glands. This results in profound aqueous-deficient dry eye, where minimal tear production is too unstable to support a lens, leading to corneal damage and severe discomfort.
Uncontrolled diabetes presents a complex challenge due to its effects on nerve function and wound healing. Prolonged high blood sugar levels can lead to reduced corneal sensitivity, meaning a person might not feel the early warning signs of a poorly fitting lens or a minor injury. The impaired circulation and slower healing associated with diabetes increase the risk of infection and complicate the recovery from any lens-related corneal trauma.
Certain chronic conditions that require long-term oxygen deprivation can also be a factor. The cornea receives its oxygen primarily from the atmosphere, and while modern lenses are highly permeable, a pre-existing systemic issue that compromises oxygen delivery to tissues can exacerbate the mild hypoxia naturally caused by a lens. This combination may lead to corneal swelling and the growth of new, unwanted blood vessels into the clear cornea.
Lifestyle and Environmental Barriers
The safety of contact lens wear relies heavily on the user’s compliance with strict hygiene and wearing schedules. Poor hygiene is a leading cause of preventable, vision-threatening complications, as the inability or unwillingness to follow cleaning and disinfection protocols introduces pathogens into the eye. Re-using daily disposable lenses, using tap water for rinsing, or failing to replace the lens case harbors bacteria and fungi, which can lead to severe infections like Acanthamoeba keratitis.
Physical or mental limitations that prevent proper handling of the lenses create an unacceptable risk. Individuals with severe tremors, advanced debilitating arthritis, or cognitive impairment may find it impossible to safely insert, remove, and clean the small, delicate lenses. This inability to manage the lenses without contamination or excessive trauma to the ocular surface is a clear contraindication.
The occupational environment must also be considered, as some professions make lens wear hazardous. Exposure to heavy dust, chemical fumes, or particulate matter can cause foreign bodies to become trapped under the lens, leading to painful abrasions and inflammation. Working in extremely hot, dry, or smoky environments can accelerate lens dehydration, causing the lens to tighten on the eye and leading to corneal stress and discomfort.
Temporary Restrictions and Medications
Some contraindications are not permanent but rather temporary restrictions put in place for safety during recovery or treatment. Any acute eye infection, such as bacterial conjunctivitis (pink eye) or a corneal ulcer, requires the immediate cessation of lens wear until the infection is completely resolved. Continuing to wear a lens during an active infection can worsen the condition, delay healing, and even lead to permanent vision loss.
Following certain eye surgeries, there is a mandatory healing period where contact lenses cannot be worn due to the delicate state of the cornea. After refractive procedures like LASIK or PRK, the corneal flap or surface must be fully stabilized, a period that lasts from a few weeks to several months. After cataract surgery, the eye needs time to heal before any foreign body, including a contact lens, can be introduced.
A variety of systemic medications can severely limit tear production, making lens wear painful and damaging. Common over-the-counter oral antihistamines and decongestants can reduce the aqueous component of the tear film, leading to dry eye symptoms that are incompatible with comfortable lens wear. More serious offenders include certain chemotherapy drugs, which can damage the lacrimal glands, and some tricyclic antidepressants, which suppress tear secretion.