Contact Lens Complications
On this page
Direct answer
Contact lens complications divide into infectious (microbial keratitis — the sight-threatening one), inflammatory (CLARE, infiltrative keratitis, giant papillary conjunctivitis, solution allergies), hypoxic (corneal oedema, neovascularisation, overwear syndrome, endothelial change), mechanical (superior epithelial arcuate lesions, 3-and-9 staining, tight-lens syndrome) and toxic. Microbial keratitis presents with pain, redness, discharge, an epithelial defect with infiltrate and anterior chamber reaction; overnight wear multiplies its risk several-fold, and every red, painful lens-wearing eye stops wearing immediately and gets examined — never patched. Acanthamoeba keratitis, the nightmare complication, shows pain out of proportion to signs, radial perineuritis and later a ring infiltrate, classically after tap-water or swimming exposure. Grading on a standard scale (Efron's 0-4) at every visit converts redness from an adjective into data.
What you must remember
- Triage law: a red eye with pain, photophobia or reduced vision in a lens wearer is presumed keratitis until examined; lens wear stops at once, and any infiltrate larger than about 1 mm, hypopyon, or central lesion refers urgently.
- Microbial keratitis: infiltrate with overlying epithelial defect, marked ciliary congestion, discharge, anterior chamber reaction; risk hierarchy — extended/overnight wear highest, daily disposables lowest; Pseudomonas the classic organism.
- CLARE (contact lens acute red eye): diffuse infiltrates, moderate pain, no epithelial defect, no discharge — an immune response to bacterial exotoxins; resolves with lens cessation, treat symptoms, no patching.
- GPC (giant papillary conjunctivitis): itchy eyes, mucus, lens intolerance, papillae on the upper tarsus graded 0-4; managed by reduced wearing time, better hygiene or daily disposables, mast-cell stabilisers, and lens refit.
- Hypoxic spectrum: acute oedema with overnight wear (haloes, steepened cornea), chronic neovascularisation beyond 1-2 mm into the cornea, overwear syndrome, and endothelial polymegathism after years of low-Dk wear — solved by higher Dk/t materials and shorter wearing schedules.
- Acanthamoeba: pain beyond signs, radial perineuritis, ring infiltrate; ask about rinsing in tap water, swimming, and hot tubs; diagnosis by confocal microscopy and culture — never steroid-mask without ophthalmology.
- Mechanical lesions: superior epithelial arcuate lesion (SEAL), 3-and-9 staining with rigid lenses, tight-lens syndrome (lens does not move on blink), and foreign-body tracking under RGP lenses.
- Grading discipline: Efron's 0-4 scale (or the five-image comparator charts) for bulbar redness, limbal injection, corneal staining, infiltrates and papillae — recorded at every aftercare so change is detectable.
Triage of the red eye at the slit lamp
A 24-year-old daily-extended-wear hydrogel user arrives with two days of pain, light sensitivity and a white spot. Sequence: vision first (6/18 from 6/6), then slit lamp — a 1.5 mm central infiltrate with epithelial defect, 2+ anterior chamber reaction, intense ciliary flush. This is presumed bacterial keratitis: lenses stop, no patch, immediate ophthalmology referral for scraping and intensive fortified antibiotics. Document the appearance, draw the infiltrate, and do not restart any lens wear until the cornea is quiet and the surface stable.
Contrast the next three chairs. Diffuse peripheral infiltrates with a comfortable eye and no defect after an overnight in an old pair — CLARE: lenses out, review in days. Itching, mucus and upper-lid papillae in a two-year soft-lens wearer — GPC: refit to daily disposables, strict rub-and-rinse, mast-cell stabiliser if needed. Bilateral haloes and hazy morning vision after sleeping in lenses — hypoxic oedema: wear stops, high-Dk material follows. Same symptom, four diseases, four endings — the skill is the sequence and the threshold to refer.
Where students slip
Calling infiltrates "sterile therefore minor": size, centrality, pain level and AC reaction decide urgency, and a sterile infiltrate can sit beside an infected one. Patching a red lens eye — never; patching accelerates infection. Missing the Acanthamoeba history: the tap-water rinse is the question that changes everything. Forgetting that complications track wear modality — the aftercare question "do you sleep in them?" outranks any test — and grading redness without a reference scale, so three visits of slow worsening never register. Finally, compliance counselling is treatment: care systems, case hygiene, replacement schedules and water avoidance prevent more disease than any drop.
Frequently asked questions
Which contact lens complication is sight-threatening and what triggers suspicion?
Microbial keratitis — pain, redness, discharge and reduced vision with an epithelial defect over an infiltrate, above all in overnight wear; it stops lens wear and refers urgently.
How does CLARE differ from infiltrative keratitis?
CLARE shows diffuse infiltrates with moderate pain but no epithelial defect or discharge (exotoxin-driven), whereas focal infiltrative keratitis shows discrete lesions that merit closer monitoring for infection.
What are the features of Acanthamoeba keratitis?
Pain out of proportion to early signs, radial perineuritis, later ring infiltrate, with tap-water or swimming exposure; suspect it early, since late disease responds poorly.
How is giant papillary conjunctivitis managed?
Reduced wearing time, daily disposable refits or better cleaning, mast-cell stabiliser drops, and lens material or edge redesign; papillae are graded at every visit.
Why must a red contact lens eye never be patched?
Patch occlusion raises temperature and retains organisms in an eye already at risk of infection; management is lens cessation, examination and, when indicated, urgent antimicrobial therapy.