# Contact Lens and Its Complications > Contact lenses for FMGE Ophthalmology: types, hypoxic and mechanical complications, giant papillary conjunctivitis, Pseudomonas and Acanthamoeba keratitis. - Canonical URL: https://prepelephant.com/topics/fmge/ophthalmology/contact-lens-fmge - Exam / course: FMGE · Subject: Ophthalmology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Contact Lens and Its Complications", PrepElephant, https://prepelephant.com/topics/fmge/ophthalmology/contact-lens-fmge ## Direct answer A red, painful eye with a white infiltrate in an overnight soft-lens wearer is microbial keratitis until the slit lamp proves otherwise — the single most consequential fact in contact lens practice. Lenses are refractive (soft hydrogels and silicone hydrogels for daily wear, rigid gas-permeable lenses that vault irregular corneas in keratoconus and high astigmatism), therapeutic (bandage lenses for epithelial healing, bullous keratopathy and post-operative comfort), cosmetic and prosthetic. Complications sort by mechanism: hypoxic (overwear syndrome, neovascularisation, contact lens acute red eye), mechanical (giant papillary conjunctivitis, tight lens syndrome, deposits) and infective (bacterial keratitis, classically Pseudomonas in extended wear, and Acanthamoeba — severe pain out of proportion to signs, a ring infiltrate, and a history of tap water or swimming in lenses). Hygiene discipline — no tap water, no overnight wear unless prescribed, rub-and-rinse cleaning, case replacement — prevents most of it. ## What you must remember - **Lens families:** soft hydrogel and silicone hydrogel (comfort, disposability); rigid gas-permeable (superior optics, the keratoconus lens); scleral lenses for severe surface disease; orthokeratology worn overnight. - **Hypoxic complications:** overwear syndrome (central epithelial oedema and haloes after a long wear day), corneal neovascularisation (response to chronic hypoxia; beyond about 1.5 to 2 mm, lens wear must stop), and contact lens acute red eye (CLARE) — sudden redness and infiltrates after sleeping in lenses. - **Giant papillary conjunctivitis:** cobblestone upper tarsal papillae, itching, mucus and lens intolerance; treatment is discontinuation, hygiene or disposable modality, mast-cell stabilisers, and steroids in the acute phase. - **Bacterial keratitis:** suppurative infiltrate with epithelial defect, hypopyon when advanced; Pseudomonas is the classic extended-wear organism, liquefactive and rapid — an emergency treated with intensive fortified or fluoroquinolone drops. - **Acanthamoeba keratitis:** pain far exceeding the clinical signs early on, radial perineuritis, then a ring infiltrate; history of tap water rinse, swimming or showering in lenses; diagnose by confocal microscopy and culture on non-nutrient agar seeded with Escherichia coli; treat with biguanides (polyhexamethylene biguanide or chlorhexidine) for months. - **Tight lens syndrome:** a lens that no longer moves on blinking after hours of wear produces a red, painful eye with corneal oedema — remove the lens and refit. - **Therapeutic uses worth quoting:** bandage contact lens for persistent epithelial defects, recurrent erosion, after photorefractive keratectomy, and to comfort eyes with bullous keratopathy. - **Non-negotiable counselling:** never rinse lenses or the case in tap water, never sleep in lenses not approved for it, replace the case frequently, and present the same day for a red painful eye. ## Managing the lens wearer with a red eye A 24-year-old sleeps in her monthly soft lenses and wakes with a red, tearing, photophobic right eye. Remove the lens first and inspect. Slit lamp: a 2 mm infiltrate with fluorescein-positive defect, 1 mm hypopyon and ciliary congestion — suppurative keratitis; the tap-rinsed lens case is a culture jar. Scrape for Gram stain and culture, start hourly fluoroquinolone or fortified antibiotics per protocol, review within 24 to 48 hours — Pseudomonas melts a cornea in a day. She heals with a peripheral scar. Her colleague later arrives with three weeks of pain exceeding all signs — a quiet eye with radial perineuritis and a partial ring infiltrate, in a swimmer who wears lenses: Acanthamoeba. Confocal microscopy and culture confirm it, months of biguanide therapy follow, with grafting only for the scarred aftermath. The contrast is the whole teaching: fast and bacterial versus slow and protozoal, and the water history usually tells you which before any test. ## Where the exam frames it Acanthamoeba vignettes are near-guaranteed: a contact lens wearer with severe pain, minimal early findings, a ring infiltrate and a water exposure history; the answers tested are the diagnosis, the culture medium (non-nutrient agar with E coli) and the drug family (biguanides). Pseudomonas is the named organism of choice whenever the stem says "extended wear" and "rapidly progressive ulcer". CLARE and GPC get discriminated by location and itch — upper lid cobblestones with itching is GPC, a diffuse red eye after lens sleep with infiltrates is CLARE. The exam also probes counselling directly: which single instruction prevents Acanthamoeba — never expose lenses to tap water. A final favourite is the therapeutic reversal: bandage lens for recurrent erosion, and rigid gas-permeable optics for keratoconus, testing that lenses are treatment, not just cosmesis. ## Frequently asked questions ### Which organism classically causes keratitis with extended soft contact lens wear? Pseudomonas aeruginosa — a rapid, suppurative, potentially perforating ulcer requiring immediate intensive antibiotic therapy. ### How does Acanthamoeba keratitis present? Severe pain out of proportion to early signs, radial perineuritis, then a ring infiltrate, in a lens wearer exposed to tap water or swimming; confocal microscopy and culture on non-nutrient agar with Escherichia coli confirm it. ### What is giant papillary conjunctivitis? A mechanical-allergic reaction of the upper tarsal conjunctiva to lens wear and deposits — cobblestone papillae, itching, mucus and lens intolerance — treated with hygiene changes, discontinuation, and topical antiallergics. ### What is the therapeutic role of a bandage contact lens? It protects and stabilises the corneal epithelium in persistent epithelial defects, recurrent erosion, bullous keratopathy and after surface laser procedures, relieving pain and promoting healing. ### Which lens type best corrects keratoconus? A rigid gas-permeable lens, whose tear lens neutralises the irregular corneal surface that soft lenses cannot.