Pharmacists occasionally field patients’ questions about contact lenses. There are numerous types of lenses and solutions, and pharmacists should not hesitate to refer patients to an eye care practitioner whenever they do not feel comfortable answering these questions.
Contact lenses have important advantages compared to eyeglasses.1,2 They move with the eye, allow the patient to have a natural field of view, do not have frames that obstruct vision, and reduce visual distortions caused by eyeglass lenses. Glasses fog up with temperature and humidity changes, and they can be spotted with rain; contacts do not share these drawbacks. Contacts are better for active sports, and they generally provide better sight when compared to eyeglasses.
Categories of Contact Lenses
Contact lenses fall into one of two general categories: soft and rigid gas permeable (RGP) lenses. There are also several other ways to categorize them, including as decorative contacts. Approximately 34 million people in the United States wear contact lenses, with soft lenses being the most common type (87%).3
Daily Wear Soft Contact Lenses: These lenses are composed of soft, flexible plastic.1,2 Their oxygen permeability allows the cornea to receive oxygen, unlike the older hard lenses that were prevalent in the 1970s. Patients usually adjust to daily wear soft lenses within several days, and these lenses are considered to be more comfortable and more difficult to dislodge than RGP lenses. More recent materials include silicone hydrogel plastics that further increase corneal oxygenation. Daily wear soft lenses are available in tinted and bifocal versions, but they cannot correct all visual problems. Patients must make regular office visits for follow-up care. These lenses soil and must then be replaced to ensure decent vision.
RGP Lenses: RGP lenses have significant advantages and disadvantages when compared to soft lenses. It may take a few weeks to become adapted to them due to greater discomfort.1,2 However, RGPs are less likely to tear, are more durable, and generally last longer. They are more resistant to buildup of deposits, and the visual acuity achieved is clearer and sharper than with soft lenses. Most visual problems can be corrected using RGP lenses. They may be better for certain patient populations, such as those with presbyopia or astigmatism. However, RGP lenses slip off the center of the eye more easily than other types. Debris can collect under the lenses, and patients require office visits for follow-up care.
Extended-Wear Reusable Lenses: Lenses known as extended wear are most often soft plastic lenses, although occasionally RGPs may be approved for overnight wear. Soft extended wear lenses may be worn overnight, continuously for 1 to 6 nights or up to 30 days.1,2 The maximum time of wear is determined by the prescriber for each patient based on the specific lens and the patient’s tolerance for extended use. These lenses cannot correct all visual problems, and patients require regular office visits for follow-up care.
Extended-Wear Disposable Lenses: These soft lenses are worn for 1 to 6 days before disposal. They require little or no cleaning.1,2 If the patient follows directions, they present minimal risk of infection. Vision may be less sharp than with RGPs. Handling may be more complicated, and they cannot correct all visual problems.
Planned Replacement Lenses: These lenses are daily wear soft lenses that are replaced according to a planned schedule, such as every 2 weeks, each month, or once every 3 months (quarterly).1,2 Cleaning and disinfection are simpler, although vision may not be as sharp as with RGPs.
Risks of Wearing Contact Lenses
Patients may ask pharmacists about certain types of ocular discomfort, each of which may indicate irritation or infection.4 These include discomfort, itching, burning, pain, or swelling; a foreign body sensation with a feeling of grittiness; excessive tears or any other ophthalmic discharge; extreme sensitivity to light; unusual redness; or blurred vision. If untreated, these symptoms can lead to corneal ulceration, worsening of infection, and blindness. Patients with these problems should be referred to their eye care professional.
Preventing Contact Lens Problems
Pharmacists can give patients several commonsense bits of advice to prevent problems.5 To reduce the risk of infection and irritation, patients should not sleep in daily wear lenses. They should only purchase lenses after a visit to an eye care professional and after receiving a prescription. The FDA alerts patients against purchasing contact lenses from gas stations, convenience stores, video stores, and other vendors who sell them illegally. It is risky to swap lenses with another person, as cross-contamination may occur. In addition, wearing lenses fitted for another person can result in permanent ocular injury or blindness. Patients should be advised to cease smoking, as smokers experience an enhanced risk of adverse reactions. Patients should not swim while wearing lenses, since water in pools, hot tubs, lakes, and oceans is not sterile. Contact wearers often ask about concomitant use of ophthalmic drops for dry eye, red eye, and allergic conjunctivitis. Although OTC eye drops for use with contact lenses are available, it is vital for patients to contact their prescribers before using any products, to confirm whether the drops are compatible with their specific lens type.
The Contact Lens Prescription
A prescription for contact lenses is a legal document issued following an examination by a legitimate prescriber (e.g., ophthalmologist, optometrist). The prescription may be filled by the issuer, an optician, or an online vendor (e.g., VisionDirect.com).6,7 Prescriptions contain such data as date of the examination, expiration date of the prescription, power of the lenses, the material and/or manufacturer of the prescribed lenses, the diameter of the lenses, and the base curve of the lenses. The Federal Trade Commission (FTC) enforces a legal requirement that patients be given a copy of their prescriptions.6 This law is meant to make the transaction “portable.” Patients should be urged to keep a copy of their prescription with other medical records. When the patient chooses a lens provider who was not the original prescriber, the seller is required to verify each prescription with the eye care provider before filling.7 It may be necessary for the patient to fax or send the prescription to such sellers to speed the process of procuring their lenses.
Safe Use of Contact Lens Solutions
The sheer complexity of the contact lens solution market defies discussion of individual products here. However, both the FDA and CDC provide several practical pieces of advice that must be followed.8,9 Patients must understand that their contact lens case can become a breeding ground for infection if not cleaned properly. They must empty the solution out after every use. Remaining solution is contaminated and has reduced disinfectant capability. Each time lenses are removed from the case, the patient should clean and rinse the case, inverting it to allow fluid to drain, and then allow it to air-dry. Cases should be replaced every 3 to 6 months.
In addition, patients should understand that cleaning via “rubbing and rinsing” is superior to rinsing alone (i.e., the “no rub” method) for cleaning lenses.10-12 To properly “rub and rinse,” the wearer places the disinfectant solution on the lens while it lies in the palm. The solution is rubbed over the lens surface for 5 to 10 seconds with the index finger of the other hand. The lens is then turned over and the process repeated. A strong stream of disinfectant solution is sprayed over both sides of the lens to remove debris, such as bacteria, proteins, and other deposits. Patients must never use saline solution or rewetting solution as a contact disinfectant, as neither is effective for that purpose.9
Pharmacists may suspect infection when patients complain of discomfort, itching, burning, severe pain, photophobia, excessive tearing, mucus discharge, blurred vision, decreased visual acuity, swelling, unusual redness, or a foreign body sensation.8,13 The symptoms may be confined to one eye only. This helps differentiate infection from allergic rhinitis, in which the eyes are pruritic, the discharge is watery, and both eyes are affected equally due to common allergen exposure.8
Bacterial infections are the most common type in contact lens wearers. They include those caused by Clostridium species (spp), Peptostreptococcus, Propionibacterium spp, and Fusobacterium spp.14 In particular, Pseudomonas infection is liable to be a rapidly progressing condition causing the development of corneal ulcers and blindness within 24 hours if left untreated.10,15 Fungal infections (e.g., from Fusarium spp) within the cornea grow slowly but can cause severe pain leading to corneal ulcer and blindness.10,16 They are highly resistant to therapy. A protozoan of the genus Acanth-amoeba is a rare cause of contact lens–related infection, with about 1 to 2 cases per million lens wearers.13,17,18 Risk factors include improper lens storage and handling or improper disinfection (e.g., using homemade solutions or tap water); wearing lenses while swimming, using a hot tub, or showering; contacting infected water; and having a history of corneal trauma.17,19 The organism can also cause blindness.
Dangers of Decorative Lenses
FDA personnel experience great apprehension with the approach of Halloween each year.8,20 The reason is the desire of some people to alter the appearance of their eyes for decorative purposes. Decorative lenses change eye colors and give the eyes a strange, startling look, such as cat eyes. The lenses are also known as zero-powered, plano, or noncorrective lenses. The FDA regulates such decorative lenses, and legislation does not allow marketing them as nonprescription items. Nevertheless, they are sold illegally at beauty shops, flea markets, convenience stores, record/video stores, and from the Internet.20 Use of lenses without a fitting by an eye care practitioner can lead to corneal ulcer, which can progress to internal ocular infection, corneal scarring, visual impairment, blindness, and loss of the eye.8
Future Uses for Contact Lenses
The future of contact lenses and their potential to help patients with medical problems is unknown. Researchers project that they may deliver medications to the eye through creation of a lens known as a drug-eluting lens.21 Prototype lenses were tested for their ability to release ciprofloxacin in a controlled, extended manner.22 The lenses were able to do so over a 4-week period during in vitro experiments.
Contact lenses may also be used to help manage diabetes. Researchers have developed lenses embedded with nanoparticles capable of reacting with glucose molecules in tears. The reaction results in a chemical change that alters the lens color. Using this innovative technology, patients with diabetes may eventually be able to eliminate fingersticks.2
When you need vision correction, there are several choices, such as eyeglasses or LASIK surgery. However, many people choose contact lenses, for which a prescription is required.
What Do I Need to Know to Wear My Lenses Safely?
You must follow the recommended wearing schedule. Be sure to wash your hands thoroughly before inserting your lenses. This will reduce the risk of infection. Never expose your contacts to nonsterile water such as tap water, bottled water, distilled water, or ocean water. If you fail to follow this vital precaution, you may get an organism known as Acanthamoeba in your eyes. This and other organisms found in nonsterile water can cause blindness, so avoidance is the best advice. Lenses should never be placed in the mouth, as saliva is full of bacteria.
What Do I Need to Know About Cleaning My Lenses?
You should recall and follow strictly all instructions given to you by your prescriber. Those relating to your lenses and lens care products are some of the most confusing and detailed. When there is any question, call or visit your prescriber. Only use the lens solutions that your eye care professional has recommended. Do not substitute another trade name, simply guessing that it will be the same as the product that was recommended to you.
Use only your own products. You should not trust others to pay sufficiently careful attention to the sterility and care of their products. Never use any product or lens solution if the tamper-proof seal has been violated, or if it has expired.
Sterile saline solutions are only to be used for rinsing lenses. They are never to be used as cleaning or disinfecting solutions. Rub and rinse your lenses as recommended by your prescriber. Cleaning and disinfecting should follow all instructions exactly. Never “top off” the contact solutions in your case. Any leftover solution should be discarded after each use. Lens solutions should never be reused.
Each time you remove your lenses, clean, rinse, and air-dry the case. Allow excess solution to drain out of your lens case by turning it upsidedown. Bacteria may grow in the case if this is not done properly.
When you travel, keep your lens solutions in their original bottles. Never transfer them to smaller containers for travel, as this can introduce infection by contaminating them. Further, the new containers will not have the appropriate labels. As a result, you may mix them up, or you may even mistakenly use another liquid that you keep in a similar container (e.g., shampoo).
When Should I See My Prescriber?
If your eyes become red or irritated, or if you experience changes in vision, you should remove your lenses immediately and make an appointment with an eye care professional.
Remember, if you have questions, Consult Your Pharmacist.
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