Appendix 2: Contact Lenses
Uses of contact lenses
•Refractive errors: people may wear contact lenses for cosmetic reasons instead of glasses. High myopes benefit from wearing contact lenses because they would need to wear thick-lensed glasses which cause visual distortion. Contact lenses afford much improved vision involving the whole visual field.
•Aphakia (see p. 156).
•Corneal abnormalities such as keratoconus (see p. 112).
•Protection: a bandage lens can protect the eye from perforating or becoming too dry. Painted contact lenses are worn by albinos or people with aniridia to prevent too much light entering the eye.
•Some people seek to have myopia corrected by the insertion of an intraocular lens surgically so they do not have to wear glasses or contact lenses.
Types of lens
•Hard or rigid lens.
•Gas-permeable lens.
•Soft lens.
•Extended-wear lens.
•Bandage lens.
•Disposable – monthly/weekly/daily.
•Toric and bi-toric for astigmatism.
•Bifocal.
Hard and gas-permeable lenses
Hard and gas-permeable lenses must be removed before sleep or if the eye is irritable. If they are kept in under these circumstances, corneal damage is likely to occur. Artificial teardrops may be required to prevent the cornea drying out. Gas-permeable lenses should cause less corneal dryness.
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Soft lenses
Soft lenses are slightly larger than hard lenses. They tend to be used if the wearer finds hard lenses intolerable. They should also be removed at night and if the eye is irritable. More scrupulous care is required for soft lenses as they are more likely to cause corneal damage; because they are made of a softer material than hard lenses, a scratch on the cornea or a small foreign body underneath the lens is not so likely to be felt until damage has been done.
Fluorescein drops should never be put into an eye with a soft contact lens in, as the dye will be taken up by the lens and is extremely difficult, if not impossible, to remove. Only eye drops without preservative should be used with soft contact lenses, as the preservative can be absorbed by the lens, which may provoke an allergic reaction. Soft lenses should be stored in normal saline if no soaking solution is available; water, whether sterile or not, will cause them to dry out.
Extended-wear lenses and bandage lenses
Extended-wear lenses and bandage lenses are essentially similar to soft lenses but are larger in size. They can be worn for up to three months without being removed, so are therefore useful for the young and the elderly. The optician removes the lens and replaces it with a new one. Artificial teardrops will be required to prevent the cornea drying out.
Bandage lenses do not have a prescription incorporated.
Disposable monthly/weekly/daily lenses
Disposable lenses are becoming more popular. Initially the lenses were designed to be worn day and night for six days and then discarded. The eyes were rested on the seventh day. Some contact lens wearers now use disposable lenses but as daily wear, removing them at night to reduce the complications (see p. 246).
Care of contact lenses
Contact lenses require great care to prevent corneal damage and eye infection. There are several different brands of products on the market for use with contact lenses. Two important steps in the care of the lenses are handwashing before and after handling the lenses and cleaning the contact lens case. There are different solutions for hard and soft lenses.
Care of lenses involves:
•Cleansing with a cleansing solution rubbed on the lens with the finger and washed off with water. It has been suggested that using solutions containing hydrogen peroxide are better in that they destroy acanthamoeba (see p. 246).
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•Wetting – wetting solution is dropped onto the corneal surface of the lens before it is inserted into the eye.
•Soaking the lens – when the lens is not in the eye, i.e. overnight, it is placed in a special container filled with soaking solution. This fluid should be changed each time the container is used. Once a week the container should be washed out with warm water and rinsed with the soaking solution.
•There are now ‘all in one’ solutions available that reduce the number of processes involved in the care process. By doing so it is hoped that the wearer will better comply with a simple regimen.
Lenses should be cleaned well and checked by an optician before being reinserted following corneal damage.
Insertion/removal of contact lenses
See p. 44 for details of how to insert and remove contact lenses.
Complications of contact lens wear
•Intolerance: some people find wearing contact lenses intolerable. Hard lenses are usually prescribed initially as they cause less problems. If these are difficult to wear, gas-permeable or soft contact lenses are prescribed. Some people have to abandon contact lens wearing and resort to spectacles.
•Corneal abrasion.
•Dry eyes: the lens prevents the tear film from adequately covering the cornea. Artificial teardrops can be prescribed for people who do experience dry eyes.
•Giant papillary conjunctivitis or contact lens associated papillary conjunctivitis. This is more common in wearers of soft contact lenses. It may not manifest itself for months or years after starting to wear lenses. Symptoms include:
itching
mucus discharge
increasing intolerance to lens wear.
Signs: large conjunctival papillae (Kanski, 2003).
•Hypoxia: the cornea is deprived of oxygen from the tear film by the presence of the contact lens. The cornea becomes oedematous and new vessels may develop in the limbal area. This usually occurs after years of contact lens wear.
•Sensitivity: this may develop in response to the preservative in the cleaning and soaking solutions.
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•Keratitis: people wearing extended-wear soft contact lenses are 21 times more likely to get microbial keratitis than gas-permeable lens wearers and daily soft contact lens wearers are four times more likely to suffer from keratitis at some point (Cochrane, 1993). Acanthamoeba is the most dangerous organism requiring intensive antibiotic application (Kanski, 2003). This may be Chlorhexidine and Polyhexamethylenebinguanide. The contact lens should not be reinserted into the eye until the infection has cleared and the lens itself has been cleaned.
It is advisable for all contact lens wearers to have a spare pair of spectacles to wear in case they are unable to use their contact lenses for a while.
Nurse’s role
Although nurses do not prescribe or fit contact lenses, they are in an ideal position to educate people on the care of contact lenses whether the person has a problem or in a more informal advisory capacity.
Nurses must stress the importance of the following:
•Complying with scrupulous and effective care regimes of their contact lenses (Wakelin, 1995; American Academy of Ophthalmologists, 2003). However, wearers of extended-wear soft contact lenses have an increased risk of keratitis despite complying with hygiene instructions (Stapleton, 1992).
•The need to discard any remaining solution after 28 days of use.
•Saliva and tap water must not be used as wetting or cleaning solutions.
•Other people’s contact lens cases, which may not be clean, must not be ‘borrowed’ for their lenses.
•Allowing time for the cornea to ‘breathe’ by removing the lenses for a period of time each day.
•Removal of lenses, except extended-wear lenses, at night.
•Washing of hands prior to handling lenses and avoiding creamy soft soaps and ensuring all traces of hand cream are removed from finger tips.
•Avoiding swimming/jacuzzis whilst wearing contact lenses.
•Removing the lenses if the eye becomes sore and seeking medical advice.
•Remove contact lenses before going to sleep.