Contact lenses (CLs) are highly regulated medical devices worn directly on the cornea. If used without proper care, they can cause serious complications such as corneal infections and corneal ulcers that may have lasting effects on vision.
The number of contact lens wearers is estimated at about 15 to 18 million 1). It has been reported that about 65% of contact lens-related corneal infections are caused by poor care 2), so both the prescriber and the wearer need to understand the care steps and the importance of regular checkups correctly.
The care required depends on the type of contact lens. Daily disposable soft contact lenses are discarded every day, so lens care is not needed 3). Two-week replacement and monthly soft contact lenses require proper daily care. To prevent corneal damage caused by inadequate care, you must follow the instructions for each product.
The two pillars of preventing contact lens-related complications are following the correct care steps and having regular eye examinations. If either is missing, the preventive effect is cut in half.
If care is neglected, the risk of corneal infections (Acanthamoeba keratitis, Pseudomonas keratitis, staphylococcal infection, etc.) and corneal ulcers rises sharply. In particular, Acanthamoeba keratitis is difficult to treat, and severe cases may require corneal transplantation. Also, if poor care continues over time, complications such as corneal neovascularization and giant papillary conjunctivitis can build up, and you may no longer be able to keep wearing contact lenses.
| CL type | Disinfection requirements | Main features |
|---|---|---|
| Hard CL (HCL) | Usually not required | Effective for corneal astigmatism and irregular astigmatism. Cleaning and rinsing are basic |
| Soft CL (SCL) daily disposable | No care needed | Discard every day |
| Soft CL (SCL) 2-week and monthly | Disinfection required | Daily care (rub, rinse, disinfect, and store) is required |
| Orthokeratology lenses | Disinfection recommended | Disinfection is recommended because of the complex shape |
All SCLs need disinfection. HCLs generally do not need disinfection, but for dirt that is hard to remove with routine care, using a dedicated cleaner is recommended. Note that abrasive cleaners cannot be used with some HCLs, so check before use.
For HCL fitting evaluation, confirming the fitting pattern with fluorescein staining is the basic approach. When there is a lot of tearing, it is easy to judge incorrectly, so evaluate after the tearing has settled. SCL fitting evaluation is judged by the push-up test and by checking whether the lens edge rides up onto the cornea when looking up, down, left, and right.
| Type | Features | Notes |
|---|---|---|
| Multipurpose solution (MPS/MPDS) | Can clean, rinse, disinfect, and store in one solution | Weak disinfecting effect against fungi and viruses. Rubbing is required |
| Hydrogen peroxide solutions | They have a stronger disinfecting effect than MPS | If neutralization is incomplete, it can cause corneoconjunctival damage |
| Povidone-iodine solutions | They have the strongest disinfecting effect | Iodine allergy is a contraindication |
Even if the disinfecting effect is increased, neglecting the basic steps of rubbing, rinsing, and cleaning and drying the lens case can cause serious eye damage such as corneal ulcers. Following the correct care steps is far more important than choosing the care solution.
Daily SCL care is performed in the following steps.
The lens case can easily become a breeding ground for biofilm (a film formed by bacteria, Acanthamoeba, and others), and if it is not handled properly, it can become a source of infection when wearing CL4).
SCLs must not be washed or stored in tap water. Tap water contains Acanthamoeba that can survive even chlorination and can cause severe Acanthamoeba keratitis. More than 90% of CL-related Acanthamoeba keratitis occurs in contact lens wearers, and contact with tap water is considered the main route of infection4). Rinsing HCLs is also recommended to be done with a dedicated care solution or saline.
Regular checkups are essential for early detection of early corneal damage without symptoms. Many contact lens wearers do not visit an eye clinic until they start to feel discomfort, but by then complications may already have progressed.
| Wearing status | Recommended interval |
|---|---|
| New wearers | Visit at 1 week, 1 month, and 3 months after starting wear5) |
| Stable wearers | At least once a year (every 6–12 months)5) |
| When problems occur | Same-day visit |
The contact lens clinical guidelines recommend at least one visit per year even for stable wearers5). New wearers should have closely spaced visits during the first 3 months to check fitting and whether any complications are present early.
For stable wearers, at least one visit per year is recommended5). New wearers should be seen at 1 week, 1 month, and 3 months after starting wear to check fitting and whether complications are present. Even without symptoms, corneal neovascularization and corneal epithelial damage can progress, so regular visits should not be skipped. Also, if there is a prescription change (a change in eyeglasses or contact lens power) or any trouble such as eye redness, pain, or blurred vision, prompt medical attention is needed.
Bacterial keratitis
Causative organisms: mainly Pseudomonas aeruginosa, Staphylococcus species, and others2)
Features: It progresses rapidly and forms a corneal ulcer. Without proper antibiotic eye drop treatment, visual impairment can remain.
Prevention: rubbing and rinsing, proper lens case care, and avoiding overnight wear
Acanthamoeba keratitis
Cause: More than 90% of cases occur in contact lens wearers. Using tap water and wearing lenses around water are the main risk factors4)
Features: Causes severe eye pain, and in the early stage it is hard to distinguish from bacterial or viral infection. It is highly resistant to treatment
Prevention: Completely avoid contact with tap water. Do not bathe or swim while wearing contact lenses
Fungal keratitis
Reports: Outbreaks of Fusarium species infections have been reported in MPS users6)
Features: Progresses slowly and is often diagnosed late. Antifungal treatment is needed
Prevention: Strictly follow care procedures. Replace the lens case regularly
Other complications
Corneal vascular ingrowth: New blood vessel growth caused by low oxygen. Consider switching to a lens with high oxygen permeability (Dk/t)
Giant papillary conjunctivitis (GPC): Papillary proliferation of the upper eyelid conjunctiva. Consider changing the type of lens and using antiallergy eye drops
Corneal epithelial damage (SPK): Shorten wearing time and use artificial tears
CL wear can increase tear evaporation and destabilize the tear film, contributing to the onset and worsening of dry eye7). The combination with long periods of screen use is especially hard on the tear film. CL-compatible artificial tears (without benzalkonium chloride: BAK-free) are recommended.
Wearing them for long periods reduces oxygen supply to the cornea and increases the risk of complications.
The use of silicone hydrogel (SiHy) contact lenses, which have high oxygen permeability, is increasing. SiHy materials are designed to reduce the cornea’s oxygen deprivation load, and deciding whether they are appropriate for each case is important.
Research is advancing on smart contact lenses equipped with eye pressure sensors and blood glucose monitoring functions9). Contact lens applications are expected for managing intraocular pressure in glaucoma and monitoring glucose in people with diabetes, but they are not yet in clinical use.
Research is progressing on infection-prevention technologies that coat contact lens surfaces with antimicrobial substances9). The goal is to further reduce the rate of contact lens-related infections through surface treatments that inhibit biofilm formation and through the application of nanomaterials.
Research is progressing on optimizing contact lens fitting using corneal shape analysis with artificial intelligence (AI). A system that supports precise contact lens prescribing tailored to each person’s corneal shape is expected to become practical.
