Contact Lens Selection
The main advantages of soft contact lenses are their comfort and shorter period of adaptation (see Table 5-3). They are available with a wide range of shapes and materials and are usually easier to fit than rigid lenses. A lost or damaged lens is readily replaced without much cost.
Soft lenses are designed for monthly, daily, and 1–2-week replacement. Very few soft lenses dispensed now are intended for longer-duration duty cycles.
Daily-wear lenses have been favored in the United States ever since reports in the 1980s showed increased incidence of keratitis with extended-wear lenses. Improved materials that have greater oxygen permeability (Dk = 60–140) have been approved for extended wear. Use of these materials may decrease the risk of infection compared with the risk associated with earlier materials, but patients who want extended-wear lenses should understand the increased risk of bacterial keratitis and the signs and symptoms that require the attention of a physician. Additional risk factors for extended-wear complications include previous eye infections, lens use while swimming, exposure to smoke, dry eye, eyelid margin disease, and allergy. Daily-wear users are exposed to the same risks, only less so.
About 10% of contact lenses fit in the United States are RGP lenses. Some with high-oxygen permeability are approved for extended wear. They are typically replaced yearly. The main advantages of RGP lenses are the high quality of vision they offer, including the correction of corneal astigmatism (see Table 5-3), durability, and simplicity of lens care. The main disadvantages of RGP contact lenses are initial discomfort, longer period of adaptation, greater knowledge and effort required for fitting, and the greater cost of replacing a lost or damaged lens. People who use contacts only sporadically are generally more comfortable with a soft lens.
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.