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Acanthamoeba keratitis occurring with daily disposable contact lens wear
  1. KENNETH J BLADES,
  2. ALAN TOMLINSON
  1. Optometry and Vision Science, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA
  2. Department of Optometry and Vision Science, City University, Dame Alice Owen Building, 311 -321 Goswell Road, London EC1V 7DD
  1. DAVID SEAL
  1. Optometry and Vision Science, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA
  2. Department of Optometry and Vision Science, City University, Dame Alice Owen Building, 311 -321 Goswell Road, London EC1V 7DD
    1. JOHN DART
    1. Moorfields Eye Hospital, London EC1V 2PD

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      Editor,—The term “disposable” contact lens is a misnomer perpetuated by the contact lens industry. Intuitively, a disposable item is discarded after use. Not so, however, for the “disposable” contact lens, as the term was introduced initially by the contact lens industry, for a lens that could be worn for 1, 2, or 4 weeks or on an extended wear basis andthen be disposed of. A later term adopted by them was “planned replacement”, which is a better description of this lens wear modality. This differs from true “daily disposable” lens wear (a recent introduction), where each pair of contact lenses is worn only once and then discarded.

      The primary difference between planned replacement and daily disposable contact lens wear is the modality of wear, not any particular feature of the contact lenses or their material. A patient could obtain daily disposable contact lenses, but decide to reuse them with appropriate cleaning and disinfection, and so would cease to be a daily disposable lens wearer and become a planned replacement lens wearer instead, though using the same contact lenses.

      The patient reported by Woodruff and Dart behaved as described above, so the authors have not reportedAcanthamoeba keratitis associated with daily disposable lens wear; they reported anAcanthamoeba keratitis infection associated with planned replacement lens wear, combined with an inadequate care regimen (saline).1 This has previously been well recorded.2 3

      It is important to warn patients that rewearing daily disposable contact lenses carries an increased risk of infection, and removes any benefit associated with this modality.

      We agree with Woodruff and Dart that patients prescribed daily disposable lenses must be warned not to reuse them. However, we do not agree that they have reported a case ofAcanthamoeba keratitis with daily disposable lens wear. There has still been no report ofAcanthamoeba keratitis with daily disposable contact lenses discarded daily. This lens wear modality affords great advantages over others, in terms of hygiene and simplicity, when used as intended. This needs to be emphasised as it is important that neither the public nor the eyecare professions are misled regarding the hygiene benefits of true daily disposable contact lenses.

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      Editor,—Our letter clearly describes a “daily disposable” lens user who developedAcanthamoeba keratitis on one occasion when she decided to “misuse” her lenses and store them overnight in saline. If we, and other researchers carrying out epidemiological studies, followed their advice and reclassified all daily disposable lens users as “planned replacement” users every time they “misused” their daily disposable lens this would make a nonsense of any analysis of risk factors, in that no daily disposable lens user would ever develop a complication from misuse of their lens because they would have become a planned replacement user by doing so. For this reason the lens should be classified by the way in which it was intended to be used and any deviations from this recorded; altering the classification after an adverse event will give rise to misleading statistics.

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