|Year : 2015 | Volume
| Issue : 2 | Page : 31-34
Spectacles in children- Do's and don'ts
Reena Sharma, Vaibhav Jain, Meenu Babber, Anupama Tandon
Department of Ophthalmology, U.P. Rural Institute of Medical Sciences and Research, Saifai, Etawah, Uttar Pradesh, India
|Date of Web Publication||3-Dec-2015|
Department of Ophthalmology, House No - 199, Civil Lines, Etawah, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Purpose: To assess the best method to prescribe spectacles in children. Source of Data: References have been collected from a MEDLINE search from 1975 to 2014. Older articles deemed not to be very contributory and those with foreign languages without any translation were omitted. The search was done using the words - spectacles, children, glasses, and prescription. Study Selection: To help and decide a proper prescription of glasses in children. Data Extraction: Internet for indexed PubMed articles. Conclusions: Children have visual needs that differ from adults, and therefore, the prescription of glasses has to be given with utmost care. They are interested in their near world and the eyes are going through a process of emmetropization. A cycloplegic refraction cannot be avoided. Many guidelines have been given based on the experience of pediatric ophthalmologists/optometrists. The basic principles, however, remain the same and should be adhered to the treatment of myopia, hypermetropia, astigmatism, and anisometropia. It is equally important to look at the spectacle frame and lenses to ensure that the prescription is used by the child.
Keywords: Astigmatism, children, hypermetropia, myopia, prescription, spectacles
|How to cite this article:|
Sharma R, Jain V, Babber M, Tandon A. Spectacles in children- Do's and don'ts. Niger J Ophthalmol 2015;23:31-4
| Introduction|| |
Children are not "scaled-down versions of adults." Their visual needs are different, and the eye is going through the process of constant change in the form of emmetropization. So, the prescription of glasses in children is not as straightforward as in adults. The difference between uncorrected and corrected visual acuity which helps us to decide on the prescription of glasses in adults, cannot be used in children.
Another often neglected and yet important part of spectacle prescription is dispensing correct spectacle frame and lenses to ensure adequate wear of glasses by the child. Most practice patterns for prescribing spectacle to young children are based on experience, rather than evidence. They are obtained by surveys of practitioners, and are based upon experience acquired over many years. 
Unlike adults, there is a huge variability of visual acuity assessment even in a child who has started speaking. So, it is difficult to use visual acuity as a criterion for prescribing glasses. Moreover, the measured acuity often underestimates the true acuity, because the child quickly get tired and may not show interest in reading small letters on an eye chart. Therefore, it is very important to do a cycloplegic refraction to determine the amount of refractive error. 
| Emmetropization|| |
The cornea and the lens, along with the axial length, form the primary refractive components of the eye. The process by which a normal eye has coordinated growth of its refractive components during early childhood to reach refraction near plano is called emmetropization.  The average cycloplegic refractive error is approximately + 2.00 D with a standard deviation of approximately 2.00 D. The keratometry at birth is ~ 52 D, compared to 42-44 D in adulthood. Axial length is ~ 17 mm at birth, enlarging to 20 mm by the end of the 1 st year,  with continued rapid growth till 2 years, and then a slow increase to 24 mm by adulthood. As the cornea flattens, the lens also thins and flattens. This would create severe hyperopia if it were not for the simultaneous axial elongation that occurs. Therefore, it is the failure of emmetropization that causes development of refractive errors in a child.
The rate of emmetropization is generally proportional to the amount of initial refractive error. Higher the initial myopia or hypermetropia, faster is the rate at which it moves toward normal. However, the probability of emmetropization decreases with increase in the amount of refractive error and chances of residual refractive error increases. 
The rate of emmetropization differs between the two eyes, which results in a period of transient anisometropia which disappears with growth of the child.  However, a large anisometropia (3.00 D or more) is more likely to be permanent.  The process of emmetropization is essentially over by 4-6 years of age. 
| When to Prescribe Glasses|| |
Many guidelines have been given to guide the amount of spectacle prescription at each age. The American Academy of Ophthalmology has published guidelines based on consensus of opinion among an expert panel.  Similarly, Miller and Harvey suggested recommendations based on consensus among members of the American Association for Paediatric Ophthalmology and Strabismus (AAPOS).  The American Optometric Association also provides guidelines for correction of hyperopia and myopia based on consensus among expert optometrists. , Many guidelines have also been suggested by individual authors. ,,,,,
The basic concepts for prescription of glasses remain the same. However, the upper limit for the prescription is variable, more so for hypermetropia. Many authors suggest monitoring the refractive error (hyperopia, myopia, or astigmatism) in infants and toddlers before prescribing glasses. ,, If the refractive errors are associated with amblyopia, they have to be prescribed. ,, However, if we find demonstrable amblyopia or heterotropia or nystagmus, we should give spectacles to the child. 
The prescription should be undercorrected in the preschool years because of active process of emmetropization. Emmetropization remains active up to 4-5 years for astigmatism and possibly up to 6 years for spherical ametropia,  and even until 9-10 years for some moderate hyperopes. ,
The majority of the infants with myopia can just be monitored as emmetropization is active, the visual world of babies is close, and they do not need clear distance vision. Only very high refractive error has to be corrected.
For correction of hypermetropia in preschool kids, Susan J Leat has suggested that one should underprescribe so as to leave the uncorrected error just above the mean refractive error for the age, leaving enough stimulus for emmetropization. 
Guidelines for myopia
In infancy, only large amount of myopia needs to be corrected, as his world is confined to seeing near objects. As the child grows and begins to walk, he starts noticing farther objects, and hence his visual demands increase. So, the spectacle prescription should be based upon anticipated visual acuity needs of the child.
More than 5 D of myopia in infancy has to be corrected. Correct >2 D of myopia in children between 1 and 4 years of age. From 4 years to early school years, −1.00 D or even lower amount if it improves VA and the child appreciates it, should be corrected.  However, one should undercorrect by about 1 D to aid the process of emmetropization. 
Older school going children (>6-year-old), when acuity can be tested accurately, warrant full correction of myopia. Here, the prescription should be according to the visual acuity of the child. Myopic children who are found to have near esophoria and larger lag of accommodation (>0.43 D) or shorter habitual reading distances may be given a + 2.00 D addition progressive lens. ,
Guidelines for hypermetropia
Uncorrected hypermetropia can produce accommodative esotropia, strabismic amblyopia, and isoametropic (refractive) amblyopia. The threshold for the treatment of hypermetropia, however, is controversial.
Many studies show that <1% of healthy children have >4 D of hypermetropia.  Atkinson et al. found that children with hypermetropia > 3.50 D had a 13 times greater risk of developing strabismus or amblyopia. These studies, therefore, suggest that hypermetropia > 4 D is definitely pathological and should be treated in all children of any age group. 
Susan J Leat has stated that >3.5 D of hypermetropia in children below 4 years, >2.50 D in 4-6 years, and >1.5 D in asymptomatic school goers (>6 years) should be prescribed. ,, Lesser than 1.5 D may be prescribed in school going children if they have associated symptoms (asthenopia, difficulty with focusing, and headaches), reduced uncorrected vision, esophoria or esotropia, and difficulty with close work. ,,
A partial prescription should be given to kids below 6 years of age to aid emmetropization. The undercorrection can be done based on Atkinson's protocol, which is based on the refraction in plus cylinder format. We should prescribe 1.00 D spherical correction less than the least hyperopic meridian and half of the astigmatism (if > 2.50 D). ,
An exception to the above guidelines for prescribing for hypermetropia is in children with developmental delay or Down syndrome. Children with significant cortical visual impairment and developmental delay may not appreciate the improvement provided by the spectacles and will not tolerate them. On the other hand, children with Down syndrome are often hypoaccommodators, and have low accommodative amplitudes. Therefore, they may benefit from even lesser amounts of spectacle correction.
Guidelines for astigmatism
Symmetric astigmatism <1.5 D typically may not be corrected, unless it is associated with high myopia or high hyperopia. The AAPOS vision screening committee has set a threshold of 1.5 D of meridional cylinder as a target condition to detect with preschool vision screening.  The American academy guidelines suggest correcting >2.5 D of astigmatism in kids below 3 years of age. Give partial correction up to 3-4 years by which time emmetropization is largely completed, that is, decrease cylinder by 1.00 D or give 50%. ,
Oblique astigmatism (compared to the other types) is a definite risk factor for amblyopia.  Therefore, even as less as 1 D needs to be corrected above 1-year of age.
In 3 to 4-year-old child, 1.50 D or more of astigmatism is associated with poorer recognition acuity, such that for every dioptre increase in cylinder, there was a half-line decrease in VA.  In older children (4 to <6 years) with 1.00 D or more of astigmatism, visual acuity is impaired.  In school going kids (above 6 years), >0.75 D cylinder should be prescribed in the absence of symptoms, and even lesser amounts if symptomatic.
Guidelines for anisometropia
If anisometropia is associated with amblyopia, it always has to be treated fully. Above 1-year of age, ≥3.00 D of anisometropia has always to be treated, because this is unlikely to be transient and is highly and likely to cause amblyopia.  The guidelines for prescribing lower amounts of anisometropia are very variable. If the child has <3.00 D of anisometropia after 1-year of age, we can monitor the child first over the next 4-6 months. If it persists, we should prescribe glasses. , For more than 1.00 D of spherical hyperopic anisometropia, >2.00 D of spherical myopic anisometropia or >1.50 D of cylindrical anisometropia after 3.5 years of age, they are likely to cause amblyopia at this age. ,,
| Spectacles Characteristics|| |
It is equally important that a child should be given proper spectacle frame and lenses. Children with photophobia (albinism, aniridia, colobomata, corneal scarring, and treated retinopathy of prematurity) are prescribed glasses with dark tints (80 − 90% tint/10 − 20% transmission) for outdoors, and lesser tints for indoors (20 − 30% tint/70 − 80% transmission). Monocular patients should be given polycarbonate lenses to protect against inadvertent eye trauma.
The spectacle frame should be of a proper size and should follow basic requirements. The eye wire should cover both the eyes completely all around permitting the patient to view from the spectacle in various ocular positions. It should not come in contact of periocular skin. The nose pads should sit symmetrically on either side of the nose bridge and should neither be too tight or loose to prevent repeated slippage or skin marks. The temples should be parallel and should put mild and symmetric pressure on the forehead without causing serious imprinting on the skin. It should not project more than 2 mm out beyond the mastoid bone.
The spectacle frame should follow the "four point touch test." All four points on the spectacle frame (two points from each side of eye wire and one each from temple) should touch the flat surface simultaneously [Figure 1].
|Figure 1: An ideal spectacle frame following the "four point touch test"|
Click here to view
The spectacle lenses should be of correct power (within ≤ 0.25 D) and correct axis of astigmatism (error ≤ 5°). The optical center of the spectacle lens should be within 2 mm of visual axis. The surface of the lens should have no fractures/pitting/scratches, as they will affect the quality of vision thereby affecting the compliance of child wearing glasses.
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Conflicts of interest
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