Although most patients are able to remove their own contact lenses, proficiency in contact lens removal is a useful skill for any clinician. Patients may present to the emergency department because of difficulty removing their own lenses or with acute ophthalmological complications of contact lens wear. Consideration should also be given as to whether patients with altered mental status (eg, comatose) may be wearing contact lenses.
Prolonged contact lens wearing times are associated with an increased risk of corneal hypoxia and edema, infection, and corneal vascularization. Contact lens removal is also necessary following ocular trauma; however, in severe trauma, where globe rupture is suspected, an ophthalmologist should be involved before any ophthalmic intervention.
The technique of contact lens removal varies slightly depending on the type of contact lens. Two main types of contact lenses are available: soft contact lenses or hydrophilic lenses, and rigid gas-permeable lenses (RGPs). A 2007 survey of prescribing habits in the United Kingdom found that soft contact lenses account for 97% of all new contact lens fits.
Soft contact lenses
These lenses are made from oxygen-permeable material. They are larger than rigid lenses but are more comfortable to wear and, therefore, are better tolerated. They may be worn monthly, continuously, or on a daily disposable basis.
Types of soft contact lens include the following:
Daily-wear contact lenses: These lenses are not suitable for wear while asleep and need to be cleaned carefully and stored.
Disposable contact lenses: These lenses are designed for short-term use. Daily disposable lenses account for 28% of the market in the United Kingdom but only 3% in the United States.
Extended-wear contact lenses: Superpermeable silicone hydrogel lenses may be worn up to 30 days continuously, even while asleep.
Rigid gas-permeable lenses
RGP lenses are made of plastic materials that do not contain water. The most popular material for their manufacture is fluorosilicone acrylate. The rigidity of hard lenses means they are generally easier to handle than soft contact lenses.
The typical RGP lens diameter is 9.8 mm (the typical soft lens diameter is13.8 mm). Rigid lenses cover only 50% of the area covered by a soft contact lens and are smaller than the cornea.
RGPs are more mobile on the eye than are soft contact lenses; therefore, they allow increased tear circulation beneath the lens. Increased tear circulation allows the transfer of more oxygen to the corneal surface.
RGPs have been shown to be statistically less likely than hydrogel materials to cause an infection. In one study comparing the relative risk of soft contact lens types to RGP lenses (the referent), extended-wear soft contact lenses had a relative risk for any complication of 2.7, compared with a relative risk of 1.3 for daily-wear soft contact lenses.