Contact lenses: hygiene and complications

What they are

Contact lenses sit on the cornea. Poor care can cause microbial keratitis (MK), scarring or the need for a transplant. This page is public education — it does not sell, fit or rank brands.

Types (classes, not brand names)

• Soft: daily, two-week, monthly; many are silicone hydrogel (SiHy) for oxygen
• Rigid gas-permeable (RGP): high oxygen; adaptation period
• Orthokeratology (ortho-K): night wear, temporary daytime refractive change; axial length is not shortened; hygiene must be strict
• Scleral lenses: larger diameter resting on the sclera; specialist fitting
• Myopia-control optical designs: discussed as a class only — no product names; children need adult help with hygiene and follow-up

Microbial keratitis risk (multi-study ballparks)

Incidence figures vary widely and are not your personal odds. A large Australian study (Stapleton et al., Ophthalmology 2008) reported about 1.9/10,000/year for daily-wear soft lenses; overnight soft about 19.5/10,000 and overnight silicone hydrogel about 25.4/10,000. A Hong Kong series (Lam et al., Eye 2002) reported about 3/10,000 for daily wear and about 9/10,000 for extended wear. Daily disposables in that Australian study had a similar overall rate to daily soft wear, with fewer severe infections reported. Figures are not a guarantee and not a brand comparison.

Even lenses labelled for continuous wear still raise infection risk overnight.

Hygiene and wear steps (education, not your personal prescription)

1. Wash and dry hands before handling; keep bottle tips and lenses off lids, surfaces and taps
2. Never rinse lenses or cases with tap water, distilled water or saliva — Acanthamoeba keratitis (AK) is linked to water
3. Discard used solution — do not save money by leaving old solution in the case and adding fresh on top; replace the case about every three months and air-dry it
4. No swimming, bathing or hot tubs in lenses; remove before showering
5. Daily disposables are single-use; no overnight wear unless a doctor has written otherwise with regular review
6. Make-up after lenses in; remove lenses before make-up removal

Water and Acanthamoeba: why even a drop matters

Acanthamoeba is widespread in environmental water (including tap-water systems). With a contact lens on, water can trap organisms between lens and cornea and raise Acanthamoeba keratitis (AK) risk. AK is uncommon but can be severely painful, hard to treat and sight-threatening — typical features are in the serious-complications table. This section covers care principles only: it does not rank which solution “kills Acanthamoeba best”, and it does not promise that switching to daily disposables means you will never get AK.

If a lens or case may have touched water: follow your fitter — often discard a daily disposable, or fully disinfect a reusable lens and decide whether to replace case/lens; if red, painful or light-sensitive, remove the lens and get same-day eye care — do not “wear one more night to see”.

Orthokeratology (OK / ortho-K): overnight hygiene education

OK is a rigid gas-permeable design worn at night to temporarily change daytime refraction. Overnight wear is linked with corneal infection risk; scarring after infection in children can affect visual development. This is hygiene and alert education — not efficacy, myopia-control magnitude or product comparison. Refractive rebound after stopping is expected; this page does not describe the eye axis as “shortened” by OK. Whether OK is used for myopia management is a prescribing / consent decision — this insert does not discuss or cite efficacy trial conclusions.

1. Before wear: wash and dry hands → inspect for cracks, deposits or damage → process with the directed system before inserting → after insertion, do not stay up long reading or on screens before sleep (routine follows the fitter)
2. Before sleep: confirm the lens is comfortable; sharp pain, severe foreign-body feel or abnormal blur — do not force sleep; remove and contact care
3. Morning removal: wash and dry hands → lubricate / mobilise as directed before removal (do not force a dry removal) → clean and disinfect at once; do not leave the lens on the sink “for later”
4. Cleaning: digital rub to clear deposits (even if a label says no-rub, many regimens still emphasise mechanical cleaning — follow written care) → discard old solution → soak in fresh solution for the full time → no tap water at any step
5. Case: empty daily; rinse with care solution (not water); air-dry face-down; replace if damaged; replace on schedule (about every three months is a common class of advice — follow your fitter)
6. Follow-up: keep reviews; discomfort, red, pain, photophobia or sudden vision drop → stop wear and same-day ophthalmology; do not “wear one more night to reshape”
7. Parent role: primary-school children often cannot judge contamination alone; supervise until the routine is stable

• OK-specific do-nots: “rinse” a rigid lens under tap water; share lenses; wear a lost-and-found lens without full disinfection
• Do not read temporary daytime blur reduction as “infection risk gone”; do not treat this site as “guaranteed-safe myopia treatment”

Common myths (hygiene)

Serious complications

Milder or chronic problems

• CLARE: red painful eye after overnight wear — still exclude infection
• Giant papillary conjunctivitis (GPC): upper-lid papillae, mucus, lens decentration; may need a break or daily disposables
• Corneal new vessels (CNV): chronic hypoxia / tight fit
• SEAL, worse dry eye, long-term endothelial loss: related to wear time and fit
• Ortho-K refractive rebound after stopping is expected — the eye is not permanently shortened

When to remove the lens; A&E vs same-day care

• Red, pain, photophobia or vision change: take the lens out now — do not “try a bit longer”
• Sudden vision drop or sudden blindness, or severe pain with vomiting: go to A&E now (see the urgent page)
• Contact-lens–related red painful photophobic eye without sudden blindness: same-day ophthalmic assessment; do not delay if pain continues after removal
• Do not self-start antibiotic or steroid drops