The key to success when dealing with refractive error in children is the early detection of the condition. Children should have their eyes examined as young as six months of age or earlier if necessary.
Eyeglasses can be prescribed to correct a variety of eye problems, but children are capable of wearing contact lenses when they are a few months old, obviously with help from their parents. Studies report that between the ages of six and eight years of age those children should be able to insert and remove lenses independently.
Contact lenses offer a wider field of view than glasses, with less prismatic effect and better depth perception, retinal image sizes and binocular fusion. The child will also have fewer worries about the weight of eyeglasses and the cosmetic appearance of lenses to correct high myopic or hyperopic vision.
Common conditions that could warrant fitting a child with contact lenses
Anisometropia, which is a significant difference in refractive error between the two eyes. Approximately 3 percent of children have this condition.
Astigmatism, which is present in two-fifths of children prior to entering school.
Nearsightedness, present in 2 percent of children entering elementary school and at least 15 percent entering high school.
Strabismus, which is a muscle imbalance that must be detected early in order to stop the development of amblyopia. Vision is a learned behavior, and if vision does not develop properly one eye will shut down.
Nystagmus, which causes involuntary oscillations back and forth movement of both eyes.
The most common use for a pediatric contact lens, however, is to correct aphakia. A child with cataracts must have them removed immediately. While adults can then be fitted with intraocular lenses, most surgeons will not do so for children under the age of two. Placing an artificial lens in the eye provides temporary vision correction, but cannot compensate for the growing eye. As the eye grows the prescription changes. An aphakic child is very farsighted and contact lenses can correct that. They also allow the corrective power to change at a reasonable price.
Types of contact lenses for pediatric use
Rigid Gas Permeable lenses
This is the best choice for treating aphakia in children. Lenses must be fitted exactly to the size of the cornea and each child must be treated individually. Keep in mind that we are dealing with small corneas and tight lids, and that we must have a large enough optic zone to accommodate the larger than normal pupil size. If the lens fits properly, there will be a normal exchange of tears between the cornea and the lens.
Soft contact lenses
Use soft lenses carefully, as concerns arise related to poor oxygen delivery when compared to RGPs and silicone hydrogel lenses. The power required for aphakic correction is very high and is associated with thick centres on the lens. Where there are differences in thickness there are differences in oxygen delivery, and that could lead to hypoxia and anoxia, possibly resulting in corneal edema, vascularization, abrasions and red-eye syndrome. Soft lenses are sometimes considered unhealthy for the small and developing eyeball.
Silicone hydrogel lenses
These lenses deliver more oxygen than RGPs and can be very comfortable. But they can be expensive and base curve and power options may be limited. Deposition is an issue with these lenses, as the composition of the tear layer varies greatly with younger eyes.
Janice Schmidt has been an optician for more than 30 years and is coordinator of the Opticianry program at Georgian College in Barrie, Ontario.