Printer Friendly FormatCHILDREN AND CONTACT LENSES
INTRODUCTION: What is a contact lens? Contact lenses are optical devices that are placed on the front surface (the cornea) of the eye to alter the refractive power of the eye. In many cases, they are an acceptable substitute for glasses with both practical and cosmetic advantages. The refractive state of the eye may be hyperopic (farsighted), myopic (nearsighted), astigmatic (unequal corneal curvatures), or a combination of these conditions (e.g. myopic astigmatism).
I. LENS CHOICES:
There are several types of lens products on the market. Each has its own advantages and disadvantages.
Hard contact lenses are the traditional contact lenses, and are made out of a non-gas permeable polymer called polymethyl methacrylate (PMMA). "Hard" contact lenses are durable and do not allow the transmission of fluids or gas through them. These lenses do not permit any transmission of oxygen through the surface of the lens to the cornea. Oxygen is transmitted to the cornea through the tear layer upon which the contact lens rides. Because of this, over-wear or irritation symptoms can occur. Although these contact lenses are often the least expensive, the aforementioned drawbacks limit their use, especially in the pediatric population.
Rigid gas permeable lenses are similar in appearance to hard contact lenses but permit diffusion of oxygen through the lens. Theses lenses are custom-made lenses which float on the cornea's tear film layer. The lenses are fit so that they are comfortable and, because the lenses are gas permeable, the risk for over-wear or discomfort is reduced. These lenses are durable, manufactured locally and are the safest type of contact lens on the market. These lenses are less susceptible to contamination as it is easier to achieve complete cleaning. Rigid gas permeable contact lenses are suited for patients with astigmatic refractions, high refractive errors, and in growing children. Because these lenses are rigid, they can be easily modified, frequently without sending them back to the manufacturer. These lenses, although initially more expensive, are ultimately more economical than other types of contact lenses because the power can be changed and they are more durable and require less maintenance.
Soft lenses (hydrophilic) are thin, flexible lenses, which have the consistency of a semi-rigid piece of Saran Wrap. These lenses are available in many stock parameters and are not custom-designed. If an eye has an unusual power requirement or corneal curvature, these lenses sometimes cannot be used. Soft lenses require disinfection with chemical solutions. These solutions reduce but do not completely eliminate the number of bacteria on the surface and within the matrix of the lens. Soft lenses, if viewed on a year-long basis, are usually more expensive than gas permeable lenses. Soft lenses can be used as extended wear or daily wear contact lenses. The FDA regulates the proper wear time and replacement schedule of contact lenses.
Extended wear lenses are soft lenses that are left on the eye overnight. We do not recommend these lenses for overnight wear in children because of the increased chance for infection associated with their use. However, extended wear lenses may be used on a daily basis (i.e., take them out at night). These lenses should be replaced at the interval recommended by the contact lens manufacturer.
Daily wear lenses are soft contact lenses that are replaced at predetermined intervals: monthly, bi-weekly, weekly or daily. These lenses should be removed each night. If these lenses are worn overnight, there is an increased risk for infection, which is concerning. These lenses do offer convenience and comfort for responsible patients.
II. INDICATIONS FOR CONTACT LENSES:
Anisometropia: The most common use of a contact lens is to correct an error of the focusing power of the eyes. The term "refractive error" is used to describe this condition. A difference between the refractive errors of the eyes of a patient is referred to as anisometropia. When anisometropia is large and it is corrected with glasses, there can be magnification or minification of the retinal image in one eye. The brain cannot fuse, or unite, these two images if the difference is great. Because the brain receives two dissimilar images, it may cause potentially permanent loss of vision in one eye (amblyopia) in children. Contact lenses are ideal to correct this problem because they reduce the size disparity between the two images that are relayed to the brain.
High refractive errors: Occasionally, contact lenses are used therapeutically for children who have myopia (nearsightedness) greater than -5.00 diopters or hyperopia (farsightedness) greater than +5.00 diopters, especially if there are difficulties in fitting glasses. Also, contact lenses may be used to correct optical distortion due to corneal disease such as keratoconus.
Cosmetic: Contact lenses can be used for cosmetic purposes. Patients who have a lack of iris tissue (aniridia) or inadequate pigment in the eye (albinism) may use tinted contact lenses to create a synthetic iris, which improves the appearance of the eye and reduces the excessive amount of light entering the eye. Another reason to use cosmetic lenses is to improve the disfigured appearance of the anterior portion of an eye with corneal scarring, white deposits, or scar tissue within the eye. This can occur after trauma or it may occur in some forms of severe intraocular disease. Cosmetic contact lenses are not recommended in the pediatric population for vanity purposes of changing the eye color because these lenses allow less transmission of oxygen due to the pigment on the lenses.
Refractive Error: Other uses for contact lenses include the correction of low refractive errors, both nearsightedness and farsightedness, as well as small degrees of astigmatism as an alternative to glasses. For example, older children often find contact lenses preferable to spectacles for athletic activities. Contact lenses are only medically necessary in a few ocular diseases. This use is purely cosmetic in all other cases. The recommendation for cosmetic use of contact lenses to correct low refractive errors will depend on the patient's interest, maturity, dexterity, level of parental supervision, and financial resources.
Therapeutic: Occasionally soft contact lenses are used to "bandage" the cornea to promote healing of its surface. These lenses are usually prescribed under close medical supervision for a limited period of time.
III.CONTACT LENS FITTING:
The use of contact lenses in a young child or an adolescent is impossible without encouragement and confidence building. Normal concerns about a contact lens "going behind" or becoming "lost" in the eye must be dispelled! Because the eye's natural reflex is to close to protect itself from foreign objects, contact lens insertion can be difficult at first. With sufficient practice of simple insertion and removal techniques, success can be achieved. The use of contact lenses in children requires parental supervision and more office visits than if spectacles were to be used. The young eye, as it grows, will require not only prescription changes but also fitting modifications as the cornea grows and changes shape. The fit of a contact lens will depend on the size, curve and surface irregularities of the cornea and the power of the optical system when the lens is on the eye. The contact lens fit is checked using a microscope (slit lamp) and, with rigid lenses, by placing some fluorescein dye in the tears and examining the eye and the fit of the contact lens with a cobalt blue light. The power is verified with a retinoscope.
IV.COMPLICATIONS/CONCERNS:
The complications of contact lens wear include corneal abrasion, the "over-wear" syndrome, infection, and non-infectious conjunctivitis.
CONTACT LENS OVERWEAR SYNDROME
The cornea requires oxygen to nourish the cells that make up the corneal tissue, especially the endothelial cells that line the inside surface of the cornea. The corneal endothelium keeps the cornea in a relatively dehydrated state. It has a pumping function that draws fluid from the cornea back into the anterior chamber. If the endothelium does not receive enough oxygen, the cornea becomes swollen with fluid. When this happens, the epithelial or surface layer of the cornea may become damaged, leading to a painful red eye. If the cornea lacks the oxygen it needs on a daily basis, then it will begin to grow new blood vessels (neovascularization) to provide itself with the needed oxygen. This can ultimately lead to decreased vision since the cornea is a clear tissue and should not have blood vessels running through it. Also because contact lenses can harbor bacteria, the constant presence of bacteria on the eye can result in the formation of subepithelial infiltrates due to an immune response, which leads to a painful red eye.
CORNEAL ABRASION
Airborne debris that would ordinarily be washed away by tears is sometimes trapped behind a contact lens. Sudden, sharp pain is experienced by the patient and the contact lens should be removed. When the eye has quieted and irritation has subsided, the contact lens can be rinsed and reinserted. If the pain persists after the contact is removed, a corneal abrasion may have occurred. This should be brought to the attention of the eye care practitioner who may patch the eye or prescribe medication for the eye. We encourage the use of sunglasses for protection from blowing wind and debris.
INFECTION
The eye surface is a warm, moist and dark (when sleeping) environment that readily supports growth of bacteria. When lenses are not properly and regularly cleaned or when the lens case is allowed to build up a biofilm, bacteria begin to grow. If contact lenses are not clean or are worn improperly, a serious infection of the cornea may occur. It is very important to consistently follow all instructions for the care, cleaning, and disinfection of contact lenses and cases to prevent such infections.
CONJUNCTIVITIS
Another complication of contact lens wear is noninfectious conjunctivitis. One type of this occurs when there is an allergic or toxic reaction to one of the ingredients of the solutions used to clean, rinse, or disinfect the lens. When this happens the eye becomes red and uncomfortable. Contact lens wear must be discontinued temporarily, and different brands of lens solutions may then be substituted to prevent recurrence.
A second type of conjunctival reaction to contact lens wear is giant papillary conjunctivitis. It is so called because of the development of large papillae on the conjunctiva overlying the tarsal plate under the upper eyelid. It can be readily observed with eversion of the eyelid. This condition is usually caused in part by the mechanical effect of the edge of the contact lens where it contacts the tarsal conjunctiva. Changing the lens type can often alleviate this problem, but sometimes contact lens wear must be discontinued for an extended period of time.
IV.YOUR CHILD AND CONTACT LENSES:
The contact lens can be a wonderful device to build self esteem and responsibility in a teenager. It provides a changeable and safe mode of optical correction for the pediatric cataract patient. With care, caution, and medical supervision, contact lens wear can lead to a lifelong enjoyment of clear vision without the use of glasses.
Pediatric ophthalmology and Strabismus, Inc.
