Contact Lens Overwear Syndrome

Contact lens overwear syndrome is corneal injury from excessive hypoxia and mechanical stress due to wearing contact lenses for too long, sleeping in them, or wearing a tight or poorly fitting lens. The classic acute form is acute hypoxic keratopathy (also called tight lens syndrome or corneal epithelial oedema), which presents with severe pain, typically waking the patient or present on waking after 4 to 10 hours of sleeping in lenses. It is a common cause of out-of-hours eye emergencies, and it must be distinguished from microbial keratitis.

• Mechanism: reduced oxygen delivery from the lens and lid closure causes epithelial oedema and sloughing, inflammatory cell infiltration, and loss of the corneal epithelium (diffuse punctate keratitis or large confluent epithelial defects). Contact lens deposits and solution toxicity add to damage.
• Risk factors: sleeping in lenses (overnight wear increases the risk of microbial keratitis 5 to 10 times), low oxygen permeability lenses, extended wear, tight fit, poor hygiene, dry eye, smoking, swimming or showering in lenses, wearing past replacement dates, solution reactions.
• Chronic overwear: corneal neovascularisation, epithelial thinning, microcysts, endothelial polymegathism, limbal stem cell stress, giant papillary conjunctivitis, reduced corneal sensitivity.
• Complications: corneal abrasion, sterile infiltrates, microbial keratitis (Pseudomonas, Staphylococcus, Acanthamoeba), scarring and vision loss.

• Sudden onset severe eye pain (often waking the person from sleep or on removing lenses), marked photophobia, tearing, a foreign body sensation, redness, blurred vision, haloes around lights, blepharospasm, swollen lids; both eyes are often affected.
• Examination: conjunctival injection, diffuse epithelial staining or sloughing on fluorescein, corneal haze, corneal oedema, sometimes small infiltrates; no hypopyon in uncomplicated cases.
• Red flags (microbial keratitis): focal white infiltrate with an epithelial defect, hypopyon, severe pain disproportionate to findings, discharge, history of water exposure, unilateral involvement, reduced vision, steroid use, poor response in 24 hours.

• Clinical, from the history of lens wear and slit lamp findings with fluorescein.
• Corneal scraping for Gram stain, culture and sensitivity, and Acanthamoeba culture or PCR, if an infiltrate or suspicious ulcer is present; culture the lens and the case.
• Intraocular pressure and anterior chamber assessment.
• Differentials: microbial keratitis, corneal abrasion, photokeratitis, viral keratitis, chemical injury from solutions, uveitis, acute angle closure, giant papillary conjunctivitis.

• Remove lenses and stop all lens wear until the eye is healed and reviewed; use spectacles. Do not patch.
• Analgesia: paracetamol 1 g orally every 6 hours and ibuprofen 400 mg every 8 hours with food; cold compresses.
• Lubricant: preservative free drops every 1 to 2 hours, with ointment at night.
• Cycloplegic: cyclopentolate 1 percent, 1 drop twice daily for 1 to 2 days for ciliary spasm.
• Antibiotic cover for an epithelial defect in a contact lens wearer (Pseudomonas must be covered): ofloxacin 0.3 percent or ciprofloxacin 0.3 percent eye drops, 1 drop four times daily for 5 to 7 days, or moxifloxacin 0.5 percent four times daily; chloramphenicol 0.5 percent is less effective against Pseudomonas.
• Do not use topical anaesthetic or steroid for home treatment.
• Microbial keratitis (infiltrate present): same day referral to ophthalmology; corneal scrape; intensive topical therapy: moxifloxacin 0.5 percent or ofloxacin 0.3 percent or levofloxacin 1.5 percent, 1 drop every hour day and night for 24 to 48 hours, then reduced; fortified antibiotics (cefuroxime 5 percent plus gentamicin 1.5 percent hourly) for severe cases; admit for severe ulcers; topical steroids only under ophthalmology supervision after infection control.
• Follow up in 24 hours for epithelial defects, then until healed (typically 2 to 4 days); then resume lens wear only when the cornea is clear, symptoms have resolved for 1 to 2 weeks and fit is checked.
• Prevention and refit: refit with silicone hydrogel lenses of high oxygen permeability; daily disposable lenses; no sleeping in lenses; limit daily wear to 8 to 10 hours; replace as scheduled; fresh solution; rub and rinse; replace the case every 1 to 3 months; no water contact; hand hygiene; remove lenses at the first sign of redness or pain.