Fitting Kids with Rigid Gas Permeable Lenses
KIDS AND RGPS
with Rigid Gas Permeable Lenses
By Jeffrey J. Walline, OD, MS
to coax kids through the RGP fitting process,
and identify which kids are potential RGP lens wearers.
Society often demands immediate satisfaction with products and medical devices on the market today. While rigid gas permeable lenses may provide immediate visual and cosmetic improvements, they are generally uncomfortable in the initial stages. Patients, especially young children, may not understand that the initial discomfort subsides with time, and the lenses can be worn without noticing any irritation. They may decide to forego contact lenses and wear their new stylish spectacles. Why should we risk wasting our valuable resources and chairtime on a patient who may not be able to adapt to contact lenses?
This article will outline reasons for fitting children with contact lenses, provide tips for making the process less difficult for children and more efficient for eyecare practitioners, detail some experiences of fitting myopic children with rigid gas permeable lenses and help you guide decisions regarding children who will be successful contact lens wearers.
RGP lenses subjectively provide clearer vision than other modes of refractive error correction, especially when worn to correct astigmatism caused by corneal toricity. RGP lenses also allow improved tear flow and oxygen under the contact lens, thereby providing ocular health benefits to the long-term lens wearer. Anecdotally, RGPs are easier to handle because they cannot invert or fold as soft lenses do and less contact time with the eye is necessary to allow the lens to settle.
Myopic children may also benefit from a reduction in the progression of myopia due to the influence of rigid contact lens wear. Perrigin and colleagues reported that myopic children fitted with RGP lenses progressed 0.53D over a three-year period, compared to 1.53D for a control group of spectacle wearers. Other studies have reported similar findings, but limitations in study design have made interpretation of results difficult.
The Contact Lens and Myopia Progression (CLAMP) study is a randomized clinical trial to examine the effects of RGP lenses on myopia progression in children. Children must successfully complete a run-in period to be enrolled in the CLAMP study. To successfully complete the run-in period, subjects must show that they can wear contact lenses at least 40 hours per week and report "always comfortable" or "usually comfortable" lens wear. Children who do not meet both of these criteria are not considered successful rigid gas permeable lens wearers, and they are not enrolled in the CLAMP study.
Some 222 children were examined for eligibility to participate in the CLAMP study. Table 1 shows eligibility criteria. Some 146 children were eligible for participation in the CLAMP study and fitted with RGP lenses. Out of the 140 children who completed the run-in period, 112 (80 percent) successfully adapted to RGP lens wear (Table 2).
Tips for the Fitting Visit
The contact lens fitting can be very traumatic for a young child because he or she does not know what to expect. A direct approach is often best, but is not universally appropriate. You may tell a child, "I am going to put a contact lens in your eye. It will feel like getting an eyelash or a piece of dust in your eye. After you wear the lens for one or two weeks, you probably won't feel it in your eye any more." Anxiety is a major factor in the child's ability to initially tolerate a contact lens, so a second pair of trial lenses may be easier to evaluate than the first.
Figure 1: A child who can tolerate holding of the eyelids is a potential candidate for RGP lens
Bennett et al. reported that the use of topical anesthetic at the fitting and dispensing visits improves adaptation to rigid lens wear. To prevent putting an additional drop in a child's eyes, place the drop of anesthetic in the contact lens prior to insertion. The effects of the anesthetic improve the child's disposition as well as the practitioner's ability to evaluate vision and lens fitting with fluorescein due to reduced tearing.
You may find that the child will squirm to avoid having something placed in the eye when you approach with the lens. If you can avoid chasing the child, the entire fitting process will be easier for both of you. Give the child a target to fixate on, firmly hold the eyelids open and stabilize the head so that you can insert the contact lens quickly. Let the child know as soon as you place the lens on the eye.
There are few differences between an adult and a child when deciding the lens parameters to order. We fit all children with a 9.2mm diameter contact lens and a 7.8mm optic zone diameter. The base curve for the initial trial lens is based on keratometry readings and the standard fitting guide found in contact lens text books (Table 3). It may be difficult to get accurate keratometry readings on a child fidgeting in the chair, but you can be more sure the readings are correct if the two eyes have similar readings, if the keratometry readings are similar to simulated keratometry readings from a corneal topographer or if two measurements of the same eye are similar.
Due to tearing and time constraints, a refraction performed over the rigid lens may not be necessary. An alignment-fitted contact lens should result in a refraction that is equal to the spherical component of the manifest refraction. We order the lens prescription based on this theory and have not had to alter the power unless an alignment fit was not achieved.
Tips for the Dispensing Visit
Depending on the child's motivation, the dispensing visit may be exciting or scary. One way to slowly adapt the child to contact lens wear is to instill a drop of topical anesthetic at the dispensing visit. The drop will again help alleviate some of the child's fears and allow for a more proper assessment of the fit and the prescription of the contact lens. The anesthetic drop may be placed in the lens prior to insertion to lessen the number of drops necessary. Insertion and removal training takes more than 15 minutes, so corneal sensation will return to normal levels by the time the child leaves your office.
Children have a fast-rising learning curve when it comes to handling RGP lenses. They regularly lose or break at least one lens in the first week, but the number of lost or damaged lenses decreases dramatically after two weeks. The first pair of lenses should be warranted, but a warranty is not necessary after the first pair unless you feel the child is less responsible than most children. Consider ordering a spare pair right away. Most lenses ordered initially will fit appropriately and provide good vision, and a contact lens lost in the early stages dramatically extends the adaptation period.
When you check the refraction over the lenses, you may find that the child accepts +0.50D to +1.00D of sphere power. When this happens, ask the child to blink hard, then recheck the power. You will probably find that the child will no longer accept the plus power. Even if the child accepts up to +1.00D over the contact lens power, recheck the power in one week. You may find that the child will encounter reduced visual acuity with +0.25D because the acceptance of plus power is probably due to excess tearing.
Successful RGP Lens Wearers
Some four out of every five children adapt to rigid gas permeable lens wear. Knowing how to predict which children can successfully wear lenses will save both you and the child many problems.
Young girls are typically more mature than boys of a similar age. While maturity plays a role in the success rate of RGP lens wearers, boys and girls equally succeeded in completing the run-in period. Even so, more girls attempted to wear contact lenses, and they account for 58 percent of the patients who are able to adapt to rigid lens wear.
Maturity is primarily an issue at the fitting visit. Some 8-year-old subjects could not distinguish the initial discomfort from pain. They were not able to comprehend that the sensation was temporary, so they cried or refused to wear contact lenses. This is fortunate in that you immediately know the child's chance of successfully adapting to lens wear. A child's ability to handle or care for RGP lenses was not dependent on the child's age. Nearly all of the children in the CLAMP study can insert, remove and care for contact lenses without assistance from their parents.
We often think that the motivation to wear lenses must belong solely to the contact lens wearer. When young lens wearers are involved, parents must also be motivated. Once outside of your office, parents must encourage the child to insert his or her contact lenses every day and help with problems that may come up during the adaptation period. Parents must also be willing to allow the child to learn on his or her own and must tolerate the additional time necessary to insert or remove lenses.
In-office indicators of success include the child's ability to tolerate eye drops and holding of the eyelids by the practitioner (Figure 1). Children who run to mommy for a hug between each eye drop or are not able to answer your questions on their own are less likely to become successful RGP lens wearers.
Occasionally a successful contact lens wearer may experience a traumatic situation such as inserting the lens without rinsing off all of the soaking solution. This single event may cause a mental block that is very difficult for the child to overcome. The child may refuse to insert the lenses because he or she fears it will hurt again. More often than not, the parents tell the child many times without success to try inserting the lens again. The eyecare practitioner's reassuring affirmation and individual coaching often helps the child overcome his or her fear.
Unfortunately, no universal predictors of success exist. Children may become successful RGP lens wearers despite initial signs that indicate the child may not be a good candidate. Two-thirds of the children who could not adapt to rigid lens wear did not report to the one week check. Most children who are not able to wear rigid lenses realize it in a relatively short period of time, which can reduce chair time.
Myopic children represent a relatively untapped population of contact lens wearers that you can recruit into your practice. The 80 percent success rate is higher than that reported for adults (69.6 percent). When examining children, be direct and honest. Children appreciate learning what to expect and a quick examination. Include the parents and the child in the examination to make them more comfortable and help you retain the patient. Above all, when examining a child, have fun and project this attitude to your patient.
References are available upon request to the editors of Contact Lens Spectrum. To receive references via fax, call (800) 239-4684 and request document #62 (Be sure to have a fax number ready).
Dr. Walline is a Senior Research Associate at the Ohio State University College of Optometry and Principal Investigator of the Contact Lens and Myopia Progression (CLAMP)
TABLE 1: Eligibility Criteria for Enrollment in the
||8 to 11 years at time of initial examination
0.75D to 4.00D spherical component, inclusive, each eye
by cycloplegic autorefraction
||20/20 or better in each eye
||Less than or equal to 1.50DC in each eye by cycloplegicv
autorefraction and less than or equal to 1.00DC on manifest refraction
No previous or attempted history of contact lens wear
||Less than or equal to 1.00D difference (spherical component)
between the eyes by cycloplegic autorefraction
||No eye disease or binocular vision problems (e.g. strabismus,
amblyopia, oculomotor nerve palsies, corneal distortion, etc.)
No systemic disease that may affect vision or vision
development (e.g. diabetes, Down syndrome, etc.)
TABLE 2:Number of Subjects at Various Stages of the CLAMP Study
|Examined for eligibility
|Not eligible to participate
|Could not complete the run-in period
|Currently participating in the run-in period
Successfully completed run-in period
and were enrolled
TABLE 3: Guide to determine the base curve from keratometry readings
||0.50D flatter than flat K
|Up to 0.75D toricity
||0.25D flatter than flat K
|0.87D to 1.37D
||Fit on flat K
||0.33 times the toricity steeper than flat K
Contact Lens Spectrum, Issue: July 2000