Contact lenses have comprised a major part of an eye doctor’s armamentarium for many years. Numerous people wear contact lenses successfully. They come in various forms, which will be discussed later. Contact lenses are the source of much pleasure and on occasion, the underlying cause of potentially severe ocular abnormalities.
Contact lenses have grown in popularity over the years. They are worn by people who are relatively young up to individuals in their 90s. They provide a cosmetic or necessary alternative to spectacles and allow a more normal appearance. With the advent of bifocal lenses, people can continue to wear lenses as long as they can see well with them and have no physical limitations with insertion or removal.
Contacts not only provide good vision but also allow for excellent peripheral vision, which is limited with higher spectacle prescriptions and frame or temple obstructions.
As long as people wear and care for their contacts as recommended by their eye care practitioners (and the FDA), usually no problems arise from normal daily wear. It is the deviation from the recommended use of contact lenses that increases the possibility of an eye infection. Proper contact lens use involves daily cleaning, periodic replacement of the contact lens case, and discarding of lenses when recommended. It is critical that patients do not overwear contact lenses. The abuse of extended wear lenses are often the underlying reason for abnormalities that lead to temporary or sometimes permanent discontinuation of contact lenses.
Types of Contact Lenses
- Hard contact lenses (also known as polymethyl methacrylate or PMMA lenses) – These are rigid lenses that are nonoxygen permeable. They fit directly on the ocular surface with a small tear layer between the back surface of the lens and the front surface of the eye. These lenses were popular until about the mid-1980s but are essentially no longer available. They could be fit as a spherical, astigmatic (toric), or multifocal lens.
- Gas permeable lenses (also known as rigid gas permeable or GP lenses) – Gas permeable lenses are similar in size, appearance, and fit to a hard lens but made out of a plastic or silicon material that is more flexible and oxygen-permeable than a traditional hard contact lens. They are available in spherical, astigmatic (toric), and multifocal designs. These are commonly used for a conventional spherical lens fit, to correct for astigmatism, or for specialty fits, such as those patients who have irregularly-shaped corneas due to scarring, trauma, or a condition that develops, culminating in a distorted cornea such as keratoconus or secondary to refractive surgery such as RK (radial keratotomy) or LASIK. If fit well, these lenses provide very sharp vision.
- Soft lenses (Hydrogel lenses) – Soft contact lenses were introduced in the 1970s and now make up 90% of new contact lens prescriptions. They are large, flexible lenses, ranging from 60% to 80% larger than conventional hard or gas permeable lenses. They offer the highest level of comfort among contact lenses and are available in spherical, astigmatic and multifocal designs. Specialty designs are available for use with disfigured eyes or artistic use. They can be worn on a daily, weekly, monthly, or extended wear basis.
- Hybrid lenses – Hybrid contact lenses are large-diameter lenses that combine a central gas permeable lens with a soft peripheral lens design. These lenses are used for irregularly-shaped corneas, such as those with keratoconus, post-RK, post-LASIK, or scars. They combine the excellent optical quality of a rigid lens with the comfort of a soft lens.
- Scleral lenses – Scleral lenses are very large gas permeable lenses that fit over the entire cornea and extend onto the white, or scleral, portion of the eye. They are used for several reasons: irregularly-shaped corneas, keratoconus, post-RK and LASIK procedures, for athletes who experience dislodged lenses, or dry eye. They are relatively comfortable and have gained in popularity.
- Bandage lenses – this is a soft contact lens that is used therapeutically to assist with treatment of a corneal abrasion instead of a pressure patch.
- Overwear syndrome – Wearing contact lenses beyond the recommended time often leads to overwear syndrome. This condition is usually characterized by a red eye, scratching or staining of the cornea or conjunctiva, GPC, neovascularization, edema (swelling), blurred vision, foreign body sensation, and/or infiltrates or ulcers.
- Red eye – Red eye is characterized by dilation of the blood vessels (referred to as injection or hyperemia) on the conjunctiva. It can be minor or quite severe. It is usually caused by a decrease in oxygen exchange, dry eye, or infection.
- Staining – Staining refers to small scratches on the corneal and/or conjunctival surface secondary to lack of oxygen exchange, a tight fitting lens, or an eye that is not receiving adequate moisture. Staining can also occur with a poorly-fitting RGP or soft contact lens or a lens fit on an irregular corneal surface.
- Giant papillary conjunctivitis (also known as GPC) – GPC is characterized by the formation under the upper lid of various-sized bumps or papilla that cause excessive movement of the contact lens, discharge, swelling of the lid, and generalized itching and discomfort. This condition is most often seen with soft contact lenses.
- Neovascularization – New blood vessel growth extending at least 2 millimeters into the normally avascularized cornea is known as neovascularization. It is usually indicative of a tightly-fitting contact lens, an extended wear lens, or a cornea that is being deprived of oxygen.
- Edema – Edema refers to swelling of the cornea. It is also caused by a tightly-fitting contact or one that is not transmitting enough oxygen through the material. This condition may be accompanied by a corneal infiltrate or an ulcer.
- Blurred vision – Blurred vision is usually caused by swelling, or edema, or a surface defect of the cornea secondary to an infiltrate or ulcer.
- Foreign body sensation – Foreign body sensation is caused by a surface defect of the cornea such as abrasion, infiltrate, or ulcer.
- Inflammation – Inflammation is characterized by increased redness or swelling externally and possibly by an internal reaction indicative of an early infiltrate or ulcer. The underlying cause is usually overwearing or sleeping in contacts.
- Infiltrate – Infiltrate refers to a possible early manifestation of a corneal ulcer. These are usually small, white circular lesions characterized by a foreign body sensation, light sensitivity, redness, swelling, possible reduction of vision, and moderate to significant pain. These require discontinuation of lenses and initiation of treatment with antibiotics and/or steroids.
- Ulcers – Ulcers are infected corneal lesions of various sizes. Usually a culture is required to determine the organism (bacterial or fungal) that is causing the symptoms. The symptoms are similar to an infiltrate but to a greater degree. Ulcers can be vision-threatening depending on their location on the cornea. Contact lenses are discontinued immediately and, depending upon the results of the culture, either easily obtained topical medication(s) may be prescribed or compounded, fortified medications will be prescribed. These are used to decrease or hopefully minimize the damage to the cornea in an attempt to spare the central cornea a permanent reduction in the visual acuity. If central scarring occurs, culminating in a significant visual reduction, a corneal transplant may be required.
For Better or for Worse
Contact lenses have had a major impact on the ophthalmic community. There have been major advances in the types of lenses available over the years. Nowadays, soft lenses are mostly fit and are available in many different modalities to be worn for various lengths of time. It is important that contact lens wearers and eye care practitioners work together to select the appropriate type of lens for each person’s lifestyle. It is equally important that contact lens wearers do not misuse their lenses. Failure to adhere to proper wear or care of lenses can result in potentially vision-threatening disorders.
More About Ocular Disease Specialist Leonard Thurschwell, O.D.
Dr. Thurschwell is a primary care optometrist with the Marietta Eye Clinic who also provides ocular surgery co-management. He earned his doctor of optometry from the Pennsylvania College of Optometry. He is a member of the American Academy of Optometry, the Georgia Optometric Association, and the American Optometric Association. He has had his research published in the Southern Journal of Optometry and the Journal of the American Optometric Association. Read more about him in his bio.
References and Additional Resources
The American Academy of Ophthalmology (AAO) is the world’s largest association of eye physicians and surgeons. It describes itself as a “global community of 32,000 medical doctors who protect sight and empower lives by setting the standards for ophthalmic education and advocating for our patients and the public.” Its website is a great resource to learn more about how to care for your eyes.
The American Optometric Association (AOA) describes itself as the leading authority on quality care and an advocate for our nation’s health, representing more than 44,000 doctors of optometry, optometric professionals, and optometry students.