Pediatric and Adolescent Contact Lens Correction

Pediatric and Adolescent Contact Lens Correction

David P. Libassi

Ralph E. Gundel

Around the world, one of the most common causes of blindness in children is the presence of pediatric cataracts (1). By advancing pediatric vision care, we hope to improve early detection of lens opacities and provide enhanced postsurgical management of pediatric aphakia. Dense amblyopia that develops from an undetected cataract or undetected high myopia requires early intervention, early optical correction, and consistent patch therapy as the steps toward ensuring a future of clear functional vision. With better detection, we can significantly reduce the number of children who suffer a life of compromised vision.

Pediatric Aphakia and High Myopia

For the infant born with a congenital cataract, most pediatric ophthalmologists prefer to remove the opacified lens within the first 4 to 6 weeks of life. If cataract extraction is not performed by 6 months of age or if postsurgical correction is ignored, dense persistent amblyopia will develop. Ophthalmic literature, however, shows that children born with congenital cataracts or significant refractive error, who receive early surgical intervention followed by consistent optical correction and amblyopia treatment, can still have compromised vision simply because they may suffer from other ocular anomalies. Children who acquire a cataract because of metabolic problems or secondary to trauma have a slightly lower risk of developing deep amblyopia. These children may have had longer visual stimulation and more normal neurologic development before cataract development (2).

Although universal agreement exists on the need for early surgical removal of the opacified lens, little agreement is seen on the best method of postoperative pediatric aphakic correction. Pediatric aphakic rehabilitation can currently be accomplished by a variety of surgical or optical devices. Epikeratophakia, and intraocular lens (IOL) implantation are two invasive surgical procedures for the correction of pediatric aphakia, whereas spectacle and contact lens correction are less-aggressive forms of optical correction for the child with significant refractive error.

Epikeratophakic procedures, once thought to be a safe and effective treatment for the child with aphakia, have largely been abandoned today. This refractive surgical correction requires removal of the corneal epithelial surface of the host eye and a lathe cut donor corneal button is sutured into place. This surgical process results in significant ocular pain, risk of epithelial in-growth, postoperative corneal inflammation, potential corneal scarring, and generally unpredictable refractive outcome (3). Epikeratophakia does not facilitate repeat procedures needed to correct for axial elongation and myopic shift as the infant eye matures through the
toddler, young child, and young adult stages of life (4,5,6).

Implantation of an IOL for pediatric aphakic correction has been a controversial topic for many years. Although the age for IOL implantation has been decreasing in recent years, most surgeons are reluctant to suggest their use in patients less than 2 years of age (7). Perceived advantages are seen for the IOL for the pediatric patient. Children who receive an IOL theoretically have less uncorrected treatment time, and their parents avoid contact lens handling and lens loss problems. It is important that practitioners and parents realize that the use of an IOL presents additional risks to ocular health and vision development in the already compromised pediatric eye. These complications include possible postsurgical inflammation, possible IOL-induced iritis, and the potential side effects of the high doses of topical steroids needed to manage the postsurgical eye. The rough and tumble life of the toddler leads to additional concern about the possible subluxation of an IOL, iris capture of a displaced IOL, and the need for repeat surgeries to remove, replace, or reposition the IOL (7,8). During the first 2 years of life alone, the increasing axial length of the eye creates 2.00 to 3.00 D of change in refractive power, requiring repeat surgical procedures to exchange the IOL. The additional 1 to 2 mm of axial length known to be added during puberty further compounds the limitations of the pediatric IOL (9,10). Add to these problems, that we do not really know the effects on ocular tissue of long-term IOL presence in the eye (7). In addition to all the ocular health concerns listed, and because it is very difficult to accurately predict the final refractive error for these children, IOL implantation becomes a less than ideal approach to pediatric aphakic vision correction (11).

Aphakic and myopic spectacle correction have been and will continue to be a safe and successful means of providing vision correction. Both monocular and binocular spectacle correction, however, present a variety of optical problems (e.g., image distortion, limitations in peripheral vision, disparities in retinal image size, fluctuations in magnitude of optical correction because of changing vertex distance in the active child, and the challenge of frame fitting with the pediatric patient) (3). Despite these problems, spectacle correction remains the least invasive form of pediatric aphakic or myopic correction.

For the pediatric patient, contact lens correction provides a means of precise refractive control with an acceptable level of ocular complications when compared with all other pediatric aphakic and myopic corrections. With a variety of contact lens materials and fitting parameters available, it is easy to find the right combination of lens material, permeability, lens parameters, and corrective power, to provide a safe and effective means of refractive correction. Clinical studies designed to compare the visual outcome of children who are pseudoaphakic with aphakic contact lens-corrected children have failed to exhibit a statistically significant difference in visual acuity 6 months following surgery (12). These studies have found that both parents and pediatric patients can do very well with aphakic or myopic contact lens correction when given adequate training and support.

Pediatric Contact Lens Materials

Contact lens options for the pediatric patient are similar to those of the adolescent or adult contact lens population. Lens material choices include silicone elastomer, spherical and toric hydrogel, and rigid gas permeable (RGP) lenses. The most frequently used contact lens for the correction of pediatric aphakia is the Silsoft lens (10). This 100% silicone lens, manufactured by Bausch & Lomb, is easy to handle, easy to maintain, and is extremely durable. The rubberlike silicone elastomer material provides high oxygen permeability with diffusion and solubility (Dk) of 340 (cm2/sec) (mL O2/mL × mm Hg), excellent thermal conductivity, and is approved for six consecutive nights of wear. The Pediatric Silsoft lens is available in an 11.3-mm diameter with steepest base curve of 7.5 mm radius followed by 7.7 mm and 7.9 mm. The lens power range starts at +20.00 D and increases in three diopter steps up to +32.00 D. The Adult Silsoft lens is available in the larger 12.5 mm diameter with base curves as steep as 7.5 mm and flattens by 0.2 mm up to an 8.3-mm radius. Because of the unique
characteristics of the silicone elastomer material, the lens is easy to handle, and is capable of correcting up to 2.00 D of corneal astigmatism. Containing only 0.02% water, the fit of a Silsoft lens is evaluated with the use of fluorescein dye applied to the tear film (13). The cost per lens to the practitioner is approximately $120.00.

Custom-made pediatric aphakic hydrogel soft contact lenses are available from a number of specialty lens manufacturers such as Continental Soft Lens, Flexlens, Kontur Kontact Lens, Ocu-Ease Optical, and Optech Incorporated. On request, specialty laboratories will provide the fitter with a 12.0-mm diameter lens, with a base curve range from 6.8 mm to 8.0 mm, and lens power between +20.00 to +40.00 D. These pediatric lenses are manufactured in 53% to 55% water content lens materials having a relatively low Dk (14). With this wide range of lens parameters, fitting a well-centered lens with adequate movement on a blink can be successfully accomplished. Because of the characteristics of hydrogel lens materials used, careful monitoring of the lens surface condition and corneal health is required. The U.S. Food and Drug Administration (FDA) Group 4 hydrogel materials used for these lenses will attract tear mucin and protein deposits during months of lens wear, reducing lens comfort and optical quality, and increasing the possibility of bacterial contamination. In addition, the reduced oxygen transmission available through these thick hydrogel lenses raises concerns about possible corneal edema. A handheld slit lamp or white light view through the magnifying lens of the Burton lamp is helpful to assess hydrogel lens movement. The cost per lens of pediatric hydrogel lenses ranges from $50.00 to $100.00.

Although slightly more challenging to accomplish, RGP contact lenses provide several advantages over all other contact lenses for the pediatric patient. RGP lenses are known for their excellent optical quality, high oxygen permeability (Dk ranging from 50 to 151), and low risk of bacterial or protein contamination. When properly fitted, RGP lenses provide significant postlens tear film exchange with each blink. These benefits typically translate into fewer corneal complications and fewer days of nonlens wear. For pediatric patients who have had traumatic eye injuries, RGP lenses offer the added benefit of correcting for significant amounts of irregular corneal astigmatism (15). In addition, replacement RGP aphakic lenses can be one third to one half the cost of a replacement silicone or hydrogel lens. The underutilization of RGP pediatric lenses is likely related to practitioner inexperience, lack of fitting sets, and perceived lens intolerance. Those practitioners with RGP pediatric lens experience report that lens adaptation and success is much better than perceived (15).

Pediatric Prefitting Examination

Fitting the infant with a pediatric contact lens typically requires little cooperation from the patient and significant cooperation from the parents. When fitting toddlers with their first contact lens, although cooperation of the child would be greatly appreciated, a significant struggle is usually the reality. As is usually recommended for pediatric patient care, avoid wearing a white coat to help reduce the child’s anxiety and enlist greater cooperation. During the first office visit, the parents must be educated about the risks and rewards of pediatric contact lens correction and their role in lens handling. These parents will be required to learn the technique for contact lens insertion, removal, and periodic eye lens evaluation. Parents will be asked to carefully study their child’s ocular appearance several times each day to determine ocular health. Parents’ willingness to learn lens handling and to be compliant with lens care and wearing instructions are critical for their child’s success.

Before lens fitting, careful evaluation of the patient’s lids, bulbar conjunctiva, and cornea are essential. Using an ultraviolet light of the handheld Burton lamp or handheld slit lamp with cobalt filter illumination, fluorescein dye can be applied to the corneal surface in an effort to identify areas of corneal compromise. If the keratometry readings taken in the operating room are unavailable, an attempt should be made to gather this information. Although keratometry is helpful, fitting without this information can proceed. It has been well established that infants and toddlers who are aphakic have steep corneal curvatures and high plus refractive errors (16,17). Selection of initial trial
lens base curve is typically based on the patient’s age. Careful observation of the trial lens centration, movement, and possible fluorescein pattern is critical for a successful fit. Retinoscopy, with handheld trial lenses, of the pediatric eye before lens fitting is helpful to determine a starting contact lens power.

For example: If neutrality in the vertical meridian is achieved with a + 18 D handheld lens, and in the horizontal meridian with + 20 D lens, these powers are averaged and then adjusted for vertex distance back to the corneal plane using the following relationship (assuming an 11-mm vertex distance): Contact lens Rx = Spectacle Rx/1 – vertex distance (in meters) × Spectacle Rx (10). This would result in the following calculated contact lens power: +19.00 D/1-[.011 (+19.00 D)] = +24.00 D.

Pediatric Contact Lens Selection

When planning to use a Silsoft pediatric lens, parameters of the initial fitting lens can be based on the age of the child. For children less than 2 years of age, start lens fitting with a 7.5-mm base curve, 11.3-mm diameter, + 32.00 D lens. As the toddler matures, it is expected that the child’s corneal curvature will flatten, aperture will enlarge, and the prescription will require less plus power. The 7.7-mm base curve lens is the starting point for children between 2 and 4 years of age, whereas the 7.9-mm base curve is for the child older than 4 years of age (16).

Pediatric hydrogel lens use should be considered when the child is in need of lens parameters not available in the Silsoft lens. Hydrogel lenses are available in high minus lens corrections, high plus corrections above +32.00 D, or base curves steeper that 7.5 mm. The specific soft contact lens parameters available from a particular manufacturer can be provided by the manufacturer’s consultation service. By providing the consultant with the on eye assessment of a pediatric diagnostic contact lens, or the age and approximate retinoscopy findings for the patient, new hydrogel lens parameters can be selected. Although the hydrogel lens insertion and removal technique is identical to the silicone soft lens technique, the inability to use fluorescein dye makes hydrogel lens fit assessment more challenging.

The use of RGP contact lenses for pediatric patients should not be overlooked. Because of their excellent safety profile, RGP lens application should be considered for children with high myopia or corneal pathology such as micro-ophthalmia or postcorneal ulcer (15,16). Although sometimes done in the operating room under general anesthesia, pediatric RGP contact lens fitting can certainly be performed in the office. The pediatric RGP trial lens set is typically composed of small (8.5 mm) diameter lenses, with base curves as steep as 5.0 mm as well as high plus and minus powers. Keratometry measurements, usually taken during the surgical procedure, can make the fitting process efficient but are not essential for fitting success. Before trial lens application, a drop of topical anesthetic should be applied to speed the trial lens process. The base curve of the first trial lens should be equal to the average of the flat and steep keratometry measurement or 7.5 mm when such measures are unknown.

Pediatric Contact Lens Insertion

Insertion of the initial pediatric aphakic trial contact lens can be one of the most challenging and rewarding contact lens procedures. A variety of methods exist to stabilize a child during the contact lens insertion and removal process. Contact lens insertion and removal during the infant stage is relatively easy and can often be done by one parent. For the completely cooperative infant, one parent may be able to hold the child and insert or remove the contact lens. The infant can be placed face up with its back on the parent’s thighs and head positioned on the parent’s knees. The infant’s legs should be wrapped around the parent’s waist (18). The parent’s nondominant hand is used to stabilize the child’s forehead while the dominant hand is used for lens insertion. When inserting a Silsoft or hydrogel lens, the thumb and forefinger of the dominant hand hold a partially pinched contact lens. The inferior one third of the lens is pinched closed, yet the top one third of the lens is completely open. As the palm of the nondominate hand stabilizes the forehead, the thumb of this hand is used to retract the upper eyelid allowing for the fanned out superior lens edge to rest on the superior bulbar conjunctiva. As
the middle finger of the lens-holding hand retracts the lower eyelid, the inferior lens edge is allowed to unfold onto the inferior cornea. When inserting an RGP contact lens, the lens should be adhered to the tip of the pointer finger by a wetting agent, and then placed directly onto the corneal apex. The upper and lower lids are slowly released and the child is allowed to blink naturally. The parent is encouraged to comfort the child as we wait for the contact lens to equilibrate.

Contact lens fitting for the 2- or 3-year-old toddler can prove to be very challenging for the experienced fitter as well as the nervous parents. Toddlers have developed the muscle strength and coordination needed to demonstrate a significant struggle during the early stages of the patient’s contact lens experience. When first introducing contact lenses to the toddler, two adults are usually needed for lens insertion and removal. One parent is needed to firmly secure the toddler while the second adult inserts or removes the contact lens. The toddler is cradled across the lap of one adult, with the toddler’s head securely nestled in the angle of the adult’s elbow. If the parent inserting the contact lens is right handed, it is helpful for the child to be secured in the angle of the holder’s right elbow. Depending on the cooperation and age of the child, this parent must concentrate on securing the body, arms, and legs of the child while comforting the child throughout the lens insertion or removal process. The child’s left arm is placed behind the holder’s body while the child’s right arm is held by the parent’s right hand, which is wrapped around the child’s head. The child’s legs may need to be secured by the holder’s left hand. Once secured, the second parent will focus on the actual lens insertion or removal process, as previously described. Releasing the child from the secure hold and comforting the child with a bottle or pacifier is recommended while waiting for the contact lens to settle down.

An alternative approach to stabilize the struggling toddler requires wrapping the child in a sheet or blanket to immobilize the child’s arms and legs (10). Once tightly wrapped in the sheet, the child is placed across the lap of the holding adult with the child’s head cradled in the angle of the right elbow. The adult manipulating the contact lens can then proceed with contact lens insertion or removal using the techniques previously described.

Parents benefit when having the complete cooperation of the infant, providing them with the best possible opportunity to learn lens handling despite the emotional challenges they may be experiencing. Starting aphakic contact lens wear as an infant gives the child the opportunity to gain comfort with the ritual of lens insertion, lens wear, and removal. Despite the formidable challenge put forth by the toddler, with determination, a firm grip, and loving care, these children learn to accept contact lens wear as part of their daily routine and demonstrate a high level of cooperation as they mature. Changes in contact lens parameters as the pediatric child matures are generally uncomplicated.

Pediatric Contact Lens Fit Assessment

The ability to use fluorescein dye to help evaluate the fit of a Silsoft pediatric aphakic contact lens is a great advantage. After 15 minutes of lens equilibration, fluorescein dye is instilled in the child’s eye. The ultraviolet lights and magnification of the Burton lamp aid in determining the Silsoft lens centration, movement, and thickness of a post-lens tear film. The ideal Silsoft lens fluorescein pattern would exhibit minimal apical clearance, minimal bearing in the intermediate zone, and peripheral edge clearance to moderate nasal edge lift. Lens movement of 1 to 2 mm is expected on a normal blink (18). If the first fitting lens demonstrates no movement, the lens is too steep and a flatter base curve should be tried. A steep-fitting Silsoft lens would demonstrate no fluorescein exchange under the lens base curve and a flatter base curve should be tried. Conversely, a flat-fitting Silsoft lens exhibits significant edge lift and excessive movement, and is easily displaced off the cornea onto the conjunctiva. When such a flat-fitting Silsoft lens has the steepest (7.5 mm) base curve, transition to a hydrogel or RGP lens is required. Hydrogel lenses are available with base curves as steep as 6.8 mm, whereas RGP lenses can be made with base curves as steep as 5.0 mm.

Unlike the silicone lens, hydrogel lenses will readily absorb fluorescein dye if it is accidentally placed in the eye. Consequently, the fit assessment for pediatric hydrogel lenses is completed using the same observation skills needed to assess a conventional or disposable hydrogel lens. After allowing 15 minutes for lens equilibration, the white light from a handheld slit lamp or ophthalmoscope is used to illuminate the lens on the eye. The practitioner must determine if the diagnostic lens demonstrates complete corneal coverage and exhibits 1 to 2 mm of movement with a natural blink. The use of a push-up test or gentle manipulation of the upper or lower lids should help determine the amount of lens float on the eye. Hydrogel lenses that move more than 2 mm with the blink or easily shift off the cornea onto the temporal bulbar conjunctiva and do not return to center with a natural blink are considered flat fitting. The next steeper base curve or larger diameter hydrogel lens should be considered in an effort to provide a more stable lens fit. Those pediatric hydrogel lenses that do not appear to move with a blink or with lid manipulation are too steep in fit and require the use of a lens with a flatter base curve. When in doubt about which diagnostic lens to dispense for trial use, it is safer to release the flatter fitting lens for daily wear use. Because of the increased center thickness of pediatric aphakic hydrogel lenses, oxygen transmission through these pediatric lenses is less than the oxygen transmission through a myopic hydrogel lens of the same material. As a result, it is very important that pediatric lenses move adequately with a blink to allow for tear film exchange under the lens.

The RGP lens assessment is performed using fluorescein dye applied to the anterior surface of a diagnostic lens. Illumination of the eye with the handheld microscope and cobalt filter, or black light of the handheld Burton lamp, is undertaken to appreciate the tear exchange under the lens. Careful and critical assessment of the central and peripheral fluorescein pattern is paramount. Time should be taken to observe the on eye lens pattern as the child blinks naturally and looks around the room. Comforting the child with a bottle or pacifier will help provide the fitter with ample time to observe the lens position and tear exchange. The ideal fluorescein dye lens pattern would represent apical alignment surrounded by a mild amount of edge lift (17). Changes in trial lens parameters, namely base curve and diameter, are made until the well-fitted RGP lens centers over the apex of the cornea and demonstrates 1 to 2 mm of movement with a blink. Although an easily displaced lens is not desired, the successful lens base curve to cornea relationship should avoid a tight adherent lens relationship.

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Jun 5, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Pediatric and Adolescent Contact Lens Correction

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