Guidelines for Prescribing Eyeglasses in Young Children

Patrick A. DeRespinis, MD

Introduction

Prescribing eyeglasses in young children is a particular dilemma for eye care professionals. No guidelines exist and practitioners frequently rely on their own experience and preconceived information, which are not always based on science. Usually, children younger than 3 years cannot offer any feedback in the decision making process of physicians prescribing spectacles. There is also a frequent lack of cooperation in children of this age group.

A child's visual requirements differ greatly from those of an adult. The development of amblyopia as it pertains to myopia, astigmatism, hyperopia, anisometropia, and strabismus, does not occur in the adult population, yet it is the most important consideration in young children. Parental and child noncompliance in treatment also impedes the practitioner from obtaining a favorable visual outcome.

A firm understanding of examination techniques is important, but knowledge of the development of the human eye and changes in refraction is essential. This tutorial reviews these areas and supplements the information with survey results gathered from the nation's pediatric ophthalmologists. Interesting trends, therapies, and controversies in prescribing eyeglasses will also be discussed.

History and Examination

The proper and comprehensive ophthalmic evaluation of a young child should include the following:

A careful history of the child's behavior at home may often reveal a potential visual deficiency. Significantly myopic children often tend to hold objects or books close to their face. They may squint and also sit close to the television, yet occasionally myopic toddlers give their parents no indication they have any visual deficiency. They tend to adapt to their visual state due to their relative lack of appreciation of normal vision.

Small to moderate amounts of hyperopia appear to be the norm in preverbal children and are accommodated well as long as esotropia does not occur. Higher amounts of bilateral hyperopia and astigmatism can cause ametropic amblyopia due to blurring of perceived images at both near and far. Anisometropic amblyopia can be particularly insidious because a relatively small amount of refractive imbalance can cause a significant unilateral visual loss that is not always detected by the parents or the pediatrician.

Children born premature, particularly those with retinopathy of prematurity, are more likely to develop myopia and/or astigmatism.1,2 The child's general health is also important because congenital and hereditary disorders can be associated with refractive errors (e.g., Down syndrome,3 Marfan syndrome,4 and Sticker disease5). Myopia can be inherited as either an autosomal dominant or autosomal recessive trait, with recessive often mistaken as a sporadic event. A good family history is essential.

Quantitating the visual acuity in a preverbal child, although not impossible, is time consuming, not always accurate, and impractical for most busy practices.6 Preferential looking techniques such as Teller7 and Cardiff8, and Vernier cards9 may provide results skewed by false positives due to observer bias and false negatives due to lack of child cooperation. Fixation responses are also obscured by the presence of underlying disorders such as nystagmus or strabismus. Children suspected of being visually impaired may also undergo electrophysiological testing such as visual evoked potentials (VEP). The results of VEPs correlate well with behavioral acuity estimates. However, unfortunately, the use of a VEP is impractical due to time restraints and cost. It is still a useful diagnostic tool in difficult cases.10,11

In the majority of practices, the detection of visual asymmetry in preverbal children is usually obtained by using small test objects of interest to the child. Using such acronyms as F&F (fix and follow) or CSM (central, steady, and maintained fixation), the visual acuity of young children is qualitatively noted on charts. The term "resistance to cover" is also an effective way to describe a dominant versus amblyopic eye. A child with strabismus who "cross fixates" usually has relatively equal vision due to the obvious lack of preference in fixation. These observations must be correlated with the entire history and the pertinent clinical findings obtained during the examination.

Possible organic disorders must be eliminated as a cause of visual impairment before eyeglasses are prescribed. Even relatively inconspicuous corneal and lenticular opacities can be the cause of visual loss in the amblyogenic period. A small retinal lesion can also cause visual loss and strabismus in young children. Therefore, a funduscopic exam is essential to rule out entities such as retinoblastoma and toxoplasmosis.

The motility evaluation is important in differentiating among forms of strabismus. Measuring the deviation at near and far and correlating the results with a good cycloplegic refraction distinguish between accommodative and nonaccommodative esotropia, and also high AC/A ratio deviations. Intermittent exotropias of the divergence excess type also vary at near and far fixation. Incomitancy of horizontal gaze can identify Duane's retraction syndrome and third and sixth nerve palsies, among other entities. Vertical imbalances can identify A and V patterns and fourth nerve palsies. Occasionally, V pattern esotropias are confused with high AC/A ratio deviations due to improper measuring technique.

Developmental Aspects and Refractive Findings

The mean axial length of a full-term infant's eye is approximately 16.5 mm with an average axial length increase of 3.75 mm in the next 18 months.12 By the age of 13 years, the mean value is 23 mm, which is near the adult mean of 24.5 mm.13 This explains why 75% of newborns have some form of hyperopia opposed to 25% having myopia.14 The mean refractive error of a full-tem infant has been found to be approximately 2 D with +/-2 D of standard deviation.15 Myopia appears to be much more common in premature infants, along with astigmatism and/or anisometropia.1,2 Anisometropia is relatively common at birth, but decreases fairly rapidly thereafter. In a normal child, hyperopia can increase to the end of the seventh year and myopia increases from age 8 to 13 years, on the average.16 Approximately 19% of normal infants have astigmatism of 1 D or more, which is at least twice the amount of adults. The trend is toward decreasing incidence of astigmatism with increasing age.17

The accommodative range has been determined to be a function of advancing age. The amplitude is approximately 14 D (+/-2 D) at 8 years of age. It decreases by 1 D every 4 years until the age of 40.18 Therefore, it is likely that a newborn has an accommodative reserve in excess of 14 D, and corrections for infants other than those with high hyperopia are unlikely.

Newborns preferentially view face-like stimuli and by 1 month of age can discriminate between a circle and a triangle. 19,20 Contrary to popular belief, a normal infant's visual system is capable of resolving a 20/20 target by at least 18 months of age.21 Fusion develops between 4.5 and 6 months of age and stereopsis has been demonstrated at approximately 3 months of age.22,23

Indications for Spectacle Correction

The following factors are indications for eyeglasses in young children. The overall visual effect of correcting the refractive error can provide multiple benefits, which may be reciprocally related:

Refractive Situations
The diagnosis of ametropic (bilateral) amblyopia can usually occur with a hyperopic correction of 5 D or higher. Amblyopia in bilateral myopia does not generally occur because of the preservation of near point vision. Unilateral high myopia can cause a significant amblyopia but may be treated with spectacles, unlike the unilateral hyperopia found in aphakia. This can be explained by Knapp's rule, which states, "If the ametropia is axial in origin, a correcting lens placed on the anterior focal plane of the eye produces an image equal in size with that of the emmetropic eye." 24 The following are refractive situations for which spectacles are prescribed:

Strabismic Situations
Generally, patients with strabismus caused by accommodative esotropia, high AC/A ratio esotropia, or forms of exotropia require eyeglasses.
Slide 1

Slide 1. Flat Top 35-type bifocals.

Slide 2

Slide 2. The improper bifocal height adjustment for a young child's eyeglasses.

When bifocals (BF) are indicated, the proper segment must be chosen:

Flat Top 35 BF (Slide 1). Fused BF segment (glass) or molded (plastic), with a thin segment line. There is a minimal blur area and the 35-mm segment covers the majority of the near visual field for a child. There is uniform power of add throughout the segment. The flat top 35 BF is the most inexpensive type of BF and is easy to fit. The optician should bisect the pupils with the segment tops (Slide 2 and Slide 3).

Slide 3

Slide 3. The correct bifocal height adjustment for a young child's eyeglasses.

Slide 4

Slide 4. Executive-type bifocals.
Executive BF (Slide 4). Molded BF segment with a front segment ridge. There is a larger blur area and the segment covers the entire near visual field. There is a uniform add power throughout the segment and they are inexpensive and easy to fit. The executive BF is not available in polycarbonate. The pupils should be bisected.

Progressive Lens (Slide 5). Multifocal, molded lens with no segment line. Cosmetically favorable with no blur area but visual distortion as you go further from the visual axis. The power of the add increases as you go downward. They are expensive and difficult to fit. In infants
Slide 5

Slide 5. A multifocal-type (Progressive) lens.
and toddlers, the frames are too small to accommodate the progressive lens and still allow for distance vision. The progressive near power must be set 4 mm higher.25 They are generally recommended in the nonamblyogenic period (older than 8 years) and in smaller deviations (ages 6 to 8 years).

Contraindications for Spectacles

The practitioner must decide whether the indications for eyeglasses outweigh the reasons for not prescribing them. These reasons include:

Emmetropization is the combination of active (visual feedback) and passive (eye growth) factors, which during development of the visual system, guide the refractive error towards emmetropia and then maintain it at an approximately emmetropic level.26

Trends in Spectacle Prescribing

Slide 6

Slide 6. The threshold amount of myopia for which ophthalmologists would prescribe eyeglasses in 1-year-old child and 2- to 3-year-old children, based upon a survey of AAPOS members.

Slide 7

Slide 7. The threshold amount of hyperopia in which ophthalmologists would prescribe eyeglasses in orthophoric children 1 year old and 2 to 3-years old, based upon a survey of AAPOS members.
Threshold Amounts of Refractive Error
U.S. pediatric ophthalmologists were asked an array of questions pertaining to spectacles in preverbal children. The prescribed threshold amounts of myopia, hyperopia, and symmetrical astigmatism in 1-year-old and 2- to 3-year-old children were the initial questions. Because of low visual demands, 1-year-old children are not prescribed myopic corrections until acuity is -4 D, whereas the majority of 2- to 3-year olds are given spectacles at -2 D to -3.75 D (Slide 6). In symmetrical hyperopia, 1-year-old children can usually tolerate larger amounts without correction because of their larger accommodative reserves. Prescribing hyperopic corrections too early may also interfere with emmetropization (Slide 7). Corrections for symmetrical astigmatism are generally given at 2.25 D to 3 D in both age groups to prevent ametropic amblyopia (Slide 8). Practitioners wait longer to prescribe astigmatic glasses in 1-year-old children due to decreased visual demands and to allow for the normal reductions in astigmatism, which occur with age.
Slide 8

Slide 8. The threshold amount of symmetrical astigmatism in which ophthalmologists would prescribe eyeglasses in 1-year-old and 2- to 3-year-old children, based upon a survey of AAPOS members.

Most ophthalmologists who responded would prescribe between 3 D and 6.25 D of correction in an orthophoric preverbal child with a 7 cycloplegic retinoscopy in both eyes. The prevention of ametropic amblyopia is the chief concern in this case because of the larger amount of hyperopia. The total amount of correction is often reduced for visual comfort since the child is orthophoric, yet it still enhances the child's ability to focus.

Anisometropia
Anisometropia is fairly common at birth but decreases rapidly over the first year. The majority of pediatric ophthalmologists are concerned with the development of amblyopia and the loss of binocular vision with hyperopic anisometropia. Fifty percent prescribe spectacles when the amount is more than 1.50 D. The responses were similar with regard to myopic anisometropia of more than -1.50 D (41%) and astigmatic anisometropia of greater than 1.50 D (60%). In unilateral high myopia (assuming one eye is -11.50 D and the other is plano), 59% prescribe the same amount in spectacle correction, while 33% utilize a contact lens. In an orthophoric child with 1.50 D in one eye and -3 D in the other, the majority of respondents maintain the difference in prescriptions with 38% giving 0.50 D and -4 D, and 23 % giving 1.50 D and -3 D, respectively.

Slide 9

Slide 9. The least amount of hypermetropia for which ophthalmologists would prescribe eyeglasses in a child 1 year of age or younger and 2 to 3 years old, assuming the child has 30 pd of esotropia, based upon a survey of AAPOS members.
Accommodative Esotropia
When queried on the least amount of hypermetropia for which eyeglasses would be prescribed in children at 1 year of age and 2 to 3 years of age, if a child had a 30 pd esotropia, the respondents chose the following: In the 1-year-old group, 49% prescribed at 2.25 D to 3 D. In the 2- to 3-year-old age group, 61% prescribed at 1 D to 2 D. Cholinesterase inhibitors were prescribed infrequently. In 1-year-old children, it is unlikely that 30 pd of esotropia will be corrected by small amounts of hyperopia, especially when hyperopia is the norm and congenital esotropia is a common entity. As the child matures, accommodative esotropia will become a more likely diagnosis and this is why we see smaller amounts of hyperopic correction prescribed (Slide 9).

High AC/A Ratio
In young children with accommodative esotropia not controlled at near with their full hyperopic correction, 62% of pediatric ophthalmologists believed the use of bifocals was necessary when 9 pd to 15 pd of esotropia was present at near fixation. Twenty-one percent prescribed BFs at 8 pd or less of esotropia. The attempt to preserve binocular vision in this age group is the reason for this trend.

Slide 10

Slide 10. The frequency bifocals are prescribed in children with high AC/A ratios not corrected at near by their hyperopic eyeglasses, based upon a survey of AAPOS members.

Slide 11

Slide 11. The frequency bifocals are prescribed in orthophoric children with myopia, based upon a survey of AAPOS members.
Bifocals
When asked how often bifocals were prescribed in children with high AC/A ratios not corrected at near by their hyperopic eyeglasses, the respondents chose to always or frequently prescribe them a total of 87% of the time (Slide 10). In contrast, bifocals in orthophoric myopes were never prescribed 87% of the time and only occasionally given in 12% of the cases (Slide 11). Obviously, bifocals in myopia are a controversial issue because properly corrected myopia is unlikely to cause asthenopia, near blurring, or myopic progression.

Exotropia
Most practitioners opt to correct vision in an attempt to control an intermittent exotropia. Sixty-three percent of respondents would treat young people with between 1.25 D and 1.75 D of astigmatic correction when exotropia is present. Few would attempt to treat this form of
Slide 12

Slide 12. The frequency minus lenses are prescribed in emmetropic or slightly hyperopic children with intermittent exotropia, based upon a survey of AAPOS members.
strabismus with "overminusing" (46% utilize it on occasion but 42% never use it). This is only a temporary therapy and leads to asthenopia and noncompliance (Slide 12).

Protection
The prescribing of polycarbonate lenses in a monocular sighted child should be standard procedure. Unfortunately, when asked, only 61% of pediatric ophthalmologists routinely prescribe them (Slide 13). Protection of the nonamblyopic eye is imperative. It is a policy statement of the American Academy of Ophthalmology, American Academy of Pediatrics, and American Association for Pediatric Ophthalmology and Strabismus, which also makes it a litigation issue if an unfortunate injury befalls an unprotected child.
Slide 13

Slide 13. The frequency polycarbonate lenses are prescribed for monocular children (one eye with vision of 20/200 or less), based upon a survey of AAPOS members.

Conclusion

In making intelligent decisions on prescribing eyeglasses in a preverbal child a clinician must:

Table 1 and Table 2 are based on a survey of the nation's pediatric ophthalmologists and the information found in this text. These tables can be used when prescribing eyeglasses in young children.

Table 1. Recommendations for Prescribing Eyeglasses in Preverbal Children*

 
Age
  0 mo to 1 yr 1 to 2 yrs 2 to 3 yrs
Myopia (symmetrical) -4 D or greater -3 D or greater -2 D or greater
Hyperopia (symmetrical
and orthophoric)		 6 D or greater† 5 D or greater† 5 D or greater†
Hyperopia (e.g.,
accommodative ET of
approx 30 pd)		 Greater than 2 D‡ Greater than 2 D‡ Greater than 1.5 D‡
Astigmatism (symmetrical) 2.50 D or greater 2.50 D or greater 2 D or greater
Anisometropia      
Myopic -2.50 D or greater -2.50 D or greater -2 D or greater
Hyperopic 2 D or greater 1.50 D or greater 1.50 D or greater
Astigmatic 2 D or greater 1.50 D or greater 1.50 D or greater

*Based on a survey of AAPOS members.
†Reduce prescription by 1 D to 2 D. If the cycloplegic refraction is greater than 7 D, the
prescription may be reduced approximately 3 D.
‡Give full cycloplegic refraction. If greater than 3 D, approximately 0.5 D may be cut
from the final prescription.

 

Table 2. Other Indications for Spectacle Correction in Preverbal Children

Bifocals in high AC/A ratios where the near deviation is greater than 10 pd to 15 pd.
Polycarbonate lenses for monocular children (one eye with 20/200 acuity or less).
Lesser amounts of astigmatism or myopia in children with X(T).
Unilateral, high axial myopia. A contact lens may also be prescribed.

 

References

  1. Fletcher MC, Brandon S. Myopia of prematurity. Am J Ophthalmol. 1955;40:474-483.
  2. Dobson V, Fulton AB, Mannino K, et al. Cycloplegic refractions of premature infants. Am J Ophthalmol. 1981;91:490-495.
  3. Caputo AR, Wagner RS, Reynolds DR, Guo SQ, Goel AK. Down syndrome: Clinical review of ocular features. Clin Pediatr. 1989;28:355-358.
  4. Maumenee IH. The eye in Marfan syndrome. Trans Am Ophthalmol Soc. 1981;79:684-733.
  5. Maumenee IH. Vitreoretinal degeneration as a sign of generalized connective tissue disease. Am J Ophthalmol. 1979;88:432-449.
  6. Geer I, Westall CA. Comparison of two preferential looking tests in the detection of amblyopia. Am Orthoptic J. 1995;45:79-89.
  7. Teller DY. Visual acuity for vertical and diagonal gratings in human infants. Vision Res. 1974;14:1433-1439.
  8. Adoh T O, Woodhouse JM, Oduwaiye KA. The Cardiff test: A new visual acuity test for toddlers and children with intellectual impairment. A preliminary report. Optometry Vis Sci. 1992;69:427-432.
  9. Holmes JM, Archer SM. Vernier acuity cards: A practical method for measuring Vernier acuity in infants. J Pediatr Ophthalmol Strabismus. 1993;30:312-314.
  10. Sokol S, Moskowitz A. Comparison of pattern VEP and preferential looking behavior in 3-month-old infants. Invest Ophthalmol Vis Sci. 1985;26:359-365.
  11. Hoyt CS. The clinical usefulness of the visual evoked response. J Pediatr Ophthalmol Strabismus. 1984;21:231-234.
  12. Blomdahl S. Ultrasonic measurements of the eye in the newborn infant. Acta Ophthalmol. 1979;57:1048-1056.
  13. Larsen J. The sagittal growth of the eye, 1. Ultrasonic measurement of the depth of the anterior chamber from birth to puberty. Acta Ophthalmol Scand. 1971;49:239-262.
  14. Cook RC, Glasscock, RE. Refractive and ocular findings in the newborn. Am J Ophthalmol. 1951;34:1407-1413.
  15. Banks MS. Infant refraction and accommodation. International Ophthalmol Clin. 1980;20:205-232.
  16. Brown EVL. Net average yearly changes in refraction of atropinized eyes from birth to beyond middle life. Arch Ophthalmol. 1938;19:719-738.
  17. Fulton AB, Dobson V, Salem D, et al. Cycloplegic refractions in infants and young children. Am J Ophthalmol. 1980;90:239-247.
  18. Duane A. Studies in monocular and binocular accommodation with their clinical applications. Am J Ophthalmol. 1922;5:865.
  19. Goren CL, Sarty, M, Wand-Wu, PYK. Visual following and pattern discrimination of face-like stimuli by newborn infants. Pediatrics. 1975;56:544-549.
  20. Milewski AE. Infant's discrimination of internal and external pattern elements. J Exp Child Psychol. 1976;22(2):229-246.
  21. Hoyt CS, Nickel BL, Billson FA. Ophthalmological examination of the infants. Developmental aspects. Surv Ophthalmol. 1982;26:177-189.
  22. Aslin RN. Development of binocular fixation in human infants. J Exp Child Psychol. 1977; 23:133-150.
  23. Fox R, Aslin RN, Shea S, Demap S, et al. Stereopsis in human infants. Science. 1980;207:323-324.
  24. Ogle KN. Researches in Binocular Vision. Philadelphia, Pa: WB Saunders Co; 1950.
  25. Smith JB. Progressive addition lenses in the treatment of accommodative esotropia. Am J Ophthalmol. 1985;99:56-62.
  26. Wildsoet CF. Active emmetropization - evidence for its existence and ramifications for clinical practice. Ophthalmic Physiological Optics. 1997;17(4):279-290.

This article was supported in part by an unrestricted grant from Research to Prevent Blindness, Inc., New York, NY.