How to achieve accurate refractions for children

Published:

Ensuring an accurate refraction is a hallmark of best practice myopia management. However refractions in children can present particular challenges. When your little patient isn't so willing or able to participate in their eye exam, how can you ensure the best oucome for them, and for your management plan? Which technique is most accurate, and when is cycloplegia necessary? Here's some tips on how to achieve accurate refractions in children. This information is relevant for examining children of all ages, but especially for pre-school aged children or those in the first few years of school, where compliance and participation in testing can be more challenging. 

Measuring visual acuity

When letters or numbers are still a learning challenge for your young patient, the LEA SYMBOLS Vision Test is specifically designed to help. It has proportionally spaced items for appropriate visual crowding, like a letter chart, with line sizing ranging from 6/38 to 6/2.4. It can be wall mounted, hand held or used with an illuminated cabinet.1 There are square, apple (or to some, a 'love heart'), house and circle optotypes. Agree on what you will call the symbols before commencing, and a hand held card can be used to identify the symbol by pointing for shy or non-verbal children. Studies investigating the sensitivity and specificity of visual acuity testing in paediatric populations found that Lea symbols yield a specificity of 79% and a sensitivity of 100%.2  76% of children can read it at age 3 and 90% of children at age 4 and over. It is recommended that an eye patch is used, and that children are directed to look at the chart before selecting an option.3

LEA

Example of the LEA Symbols vision test, compared to a Landolt C corresponding to the same visual acuity. From Becker et al 2002.1

"Tumbling E's" are another option for non-verbal acuity testing, where the examiner asks which direction the E is pointing, and the patient indicates the direction the prongs. By the age of 8-9, most neurotypical children are competent to read eye charts. A Snellen chart should be used, with crowding bars or multiple line display.2,4

The Cardiff Acuity Test (CAT) is a fun way to test acuity in non verbal children who aren’t keen to point at pictures. The pictures (duck, house, car) are printed either at the top or the bottom of a card. The examiner shows the child the card, and asks “where’s the (shape)”? Watching carefully, the patient’s eyes may flick up, or down, indicating they can see the shape. Some studies have suggested that the Cardiff cards may overestimate the visual acuities however, so aim to use Snellen or Lea symbols if possible for more comparative measures over time.5

Optometry Australia’s Paediatric Eye Care Reference Guide includes recommendations on both suitable acuity and refraction techniques for children, based on their age. An excerpt from the Guide is below.

Excerpt from Optometry Australia’s Paediatric eye care reference guide, Table 1, which outlines the potential components of a comprehensive vision and eye health examination for different age categories. Optometry Australia recommends that “each consultation is tailored to suit the needs of the individual child. Factors to consider include their ability to comprehend and undertake tests as well as clinical need based on presentation and symptoms.” Note that this provides a potential list of suitable examiniation techniques – not all techniques are likely to be needed for an individual child, dependent their individual clinical presentation.

Cycloplegic Refraction

The World Health Organisation in their report The Impact of Myopia and High Myopia suggests cycloplegic refraction for the diagnosis and correct prescribing for patients with myopia, where indicated.6 Cycloplegic refraction is recommended before treatment and to confirm changes in prescription, especially in younger children, and is seen in some instances as gold standard. It is definitely the gold standard for research reporting refractive outcomes of myopia control treatments.

Is cycloplegia necessary for myopia management?

The International Myopia Institute (IMI) Clinical Management Guidelines8 does not necessitate cycloplegic refraction at each examination of a myopic child. From section 4 on 'Key Elements of the Baseline Exam for Myopia Control':

Refraction: noncycloplegic and/or cycloplegic refraction as indicated. The IMI – Defining and Classifying Myopia Report defines myopia by refraction “when ocular accommodation is relaxed. These definitions avoid the requirement for objective refraction so as to be independent of technique, but by making reference to relaxation of accommodation are compatible with both cycloplegic and standard clinical subjective techniques.” If used, the recommended dosage for cycloplegic refraction is two drops of 1% tropicamide or cyclopentolate given 5 minutes apart. Cycloplegic refraction should be performed 30 to 45 minutes after the first drop is instilled. For more information on specific refraction techniques that have been used in myopia control studies, refer to the IMI – Clinical Myopia Control Trials and Instrumentation Report.

Which cycloplegic agent should be used?

The International Myopia Institute (IMI) Clinical Myopia Trials and Instrumentation Report7 reviews options for cycloplegia and states that "either 1% cyclopentolate or 1% tropicamide may be utilized... on average one drop of 1% tropicamide produced 0.14D more myopic refractive error measures than one drop of of 1% cyclopentolate. Mutti and colleagues also found this characteristic (0.20 + 0.30 D) in a prospective study." Each of these examples was using autorefraction.

The aforementioned report also states that the "recommended regime that has been used in multiple clinical trials is two drops of 1% tropicamide separated by 5 minutes with primary outcome measures [refraction] commencing 30 minutes after the first drop of tropicamide is instilled. Given the unnecessarily longer-lasting cycloplegic and mydriatic effects of cyclopentolate versus 1% tropicamide as well as minimal additional gain in cycloplegia with cyclopentolate in myopic children, 1% tropicamide is recommended in optical treatment studies."

A meta-analysis of six studies comparing cyclopentolate and tropicamide has shown that tropicamide refractions are on average 0.175D more myopic. This difference was not statistically significant overall, but it was when considering refractions in children, hyperopic patients or when using retinoscopy compared to an autorefractor. In each of these cases, the refraction difference between the cycloplegic agents was 0.25D or less.

As an eye care practitioner, you will know best when cycloplegia is necessary, particular to your scope of practice and the individual child's presentation. There is consensus, though, on when cycloplegia is crucial in paediatric management.

When is cycloplegia necessary?

The American Optometric Association's Clinical Practice Guideline on Pediatric Eye and Vision Examination includes a consensus statement on refraction (pg 23 - emphasis added) which states that "Cycloplegic retinoscopy is the preferred procedure for the first evaluation of school-age children. It is necessary to quantify significant refraction error in the presence of visual conditions such as strabismus, amblyopia, and anisometropia."

The bottom line is that any potentially amblyogenic situation - whether due to a complex refraction or strabismus - is worthy of cycloplegic refraction.

How can I accurately refract children without cycloplegia?

As cited by the IMI Clinical Management Guidelines,8 cycloplegic refraction is an important tool to use as indicated. There are two important points to emphasise from the excerpt above.

  1. 'As indicated' does not mean you have to undertake cycloplegia to manage myopia - it may not be available in your country, may not be suitable for that child, or may not be needed if ocular accommodation is otherwise relaxed.
  2. 'When ocular accommodation is relaxed' refers to utilization of other clinical techniques such as contralateral fogging during refractive error assessment, to prevent a blur-driven accommodative response influencing the outcome.

Performing cycloplegic versus non-cycloplegic retinoscopy on children has been shown to yield comparative results (mean of 0.30D higher plus with cycloplegia) when fogging the contralateral eye by +6.00D.

Conventional fogging is typically around +2.00D for static retinoscopy. Can you have too much fogging? One study of retinoscopy in adults tested fogging of the contralateral eye in 1D increments from zero to 6D, and found that up to 5D there was no significant change in mean refractive state. At 6D of fogging, however, there was a slight mean myopic shift of 0.13D, and up to 0.60D in some participants. The authors concluded that "the practitioner merely needs to ensure that the nontested eye is indeed fogged. The magnitude of fog present will have only minimal effect on the final result."10

One key limitation of cycloplegic refraction is that because of the artificially relaxed accommodation, it does not allow for representative assessment of binocular vision function with a new correction. In this case, non-cycloplegic retinoscopy with fogging is the preferable technique.

Retinoscopy is best

Retinoscopy is the best screening tool for detection of refractive error in children,11 especially in children up to age 7. It’s no secret how we feel about retinoscopy here at Myopia Profile - Kate wrote a whole Ode to My Retinoscope! For paediatric practice, there is no doubt that it is an effective and accurate prescription tool, and can easily be undertaken using a trial frame and/or over the current correction.

As mentioned above, if cycloplegia is not available or not necessary for your young myopic patient, non-cycloplegic retinoscopy with fogging is the ideal refraction technique as it allows assessment of both refraction and the binocular vision response to a new correction, without the situation of an artificially underactive accommodation system.

Retinoscopy is the best screening tool for detecting refraction and amblyogenic risk when done by a competent optometrist or ophthalmologist, and has been demonstrated as accurate.11,12

The American Optometric Association's Clinical Practice Guideline on Pediatric Eye and Vision Examination includes a consensus statement on refraction (pg 23 - emphasis added) which states that retinoscopy is the preferable technique for school aged children. It states that subjective refraction techniques for adults can be used in school aged children, but autorefraction is best used as a starting point for other refraction techniques.

Optometry Australia’s paediatric eye care reference guide lists retinoscopy as the primary refraction technique for children aged from birth to less than 7 years, and includes retinoscopy as part of suggested refraction techniques for children aged 7-14 years, along with subjective refraction. It does not include recommendation of autorefraction for paediatric refractions.

Autorefraction

The American Academy of Ophthalmology recently compiled a report on the levels of evidence on autorefraction. They found that:

The mean rate of error for auto-refraction is +/- 0.50D, however the variance can span from -3.55D incorrect result to +3.65D; which is a significant problem.

The review stated that other studies found myopia is often overestimated and hyperopia underestimated with autorefraction.13 Interestingly however, the review of studies found children could participate successfully in autorefraction from three months of age, and that tabletop and hand held autorefraction devices gave similar results.14 Whilst a useful tool as a starting point, especially for more complex refractions, autorefraction doesn't replace retinoscopy or subjective refraction where possible.

Autorefraction does seem to improve in accuracy with cycloplegia, showing less overestimation of myopia and more accurate detection of higher levels of hyperopia. The difference can be up to a whole dioptre in younger children; suggesting you may want to consider cycloplegic refraction if you are incorporating autorefraction in to your examination results.15

The American Optometric Association's Clinical Practice Guideline on Pediatric Eye and Vision Examination (pg 23) states that "autorefraction may be used as a starting point for subjective refraction, but not as a substitute for it; however, retinoscopy, when performed by an experienced clinician, is more accurate than automated refraction for determining a starting point for non-cycloplegic refraction."

Avoid amblyogenic situations

When making paediatric prescribing decisions, key considerations for myopes including avoiding under-correction,16 as well as addressing amblyogenic risk factors such as astigmatism or anisometropia. It has been established that full optical correction for children under five reduces the amount of adulthood amblyopia.17

Patience pays off

Eye examinations can be a challenge for little people, and I can’t deny I’ve been cried at, kicked and given some serious toddler stink-eye. I’ve also done multiple retinoscopies under my desk, and was once mistaken for the dreaded hairdresser - he had quite a nice time once we established that I wasn’t going to cut his hair. Repeated reassurance, adaptability, getting siblings or parents to help with fixation, handing out stickers and sometimes a second appointment can all be helpful in achieving an accurate paediatric refraction.

Cassandra Haines BIO image 2019_white background

About Cassandra

Cassandra Haines is a clinical optometrist, researcher and writer with a background in policy and advocacy from Adelaide, Australia. She has a keen interest in children's vision and myopia control.

This educational content is brought to you thanks to unrestricted educational grant from

References

  1. Becker, R., Hübsch, S., Gräf, M. H. & Kaufmann, H. Examination of young children with Lea symbols. British Journal of Ophthalmology 86, 513-516, (2002). (link)
  2. Shallo-Hoffmann, J., Coulter, R., Oliver, P., Hardigan, P. & Blavo, C. A study of pre-school vision screening tests' testability, validity and duration: do group differences matter? Strabismus 12, 65-73, (2004). (link)
  3. Eye examination and vision screening in infants, children, and young adults. American Academy of Pediatrics Committee on Practice and Ambulatory Medicine, Section on Ophthalmology. Pediatrics 98, 153-157 (1996). (link)
  4. American Optometry Association. Comprehensive Paediatric Eye and Vision Examination. (American Optometric Association, St Louis, 2017). (link)
  5. Sharma, P. Comparative evaluation of teller and cardiff acuity tests in normals and unilateral amblyopes in under-two-year-olds. et al. in Indian J Ophthalmol Vol. 51 (2003). (link)
  6. WHO. The Impact of Myopia and High Myopia. (World Health Organisation with the University of New South Wales, Sydney, Australia, 2015). (link)
  7. Wolffsohn JS, Kollbaum PS, Berntsen DA et al IMI – Clinical Myopia Control Trials and Instrumentation Report. Invest Ophthalmol Vis Sci 2019;60:M132-M160. (link)
  8. Gifford KL, Richdale K, Kang P. et al IMI – Clinical Management Guidelines. Invest Ophthalmol Vis Sci 2019;60:M184-M203. (link)
  9. Yeotikar NS, Bakaraju RC, Roopa Reddy PS, Prasad K.(2007) Cycloplegic refraction and non-cycloplegic refraction using contralateral fogging: a comparative study, Journal of Modern Optics, 54:9, 1317-1324 (2007). (link)
  10. Chiu NN, Rosenfield M, Wong LC. Effect of contralateral fog during refractive error assessment. J Am Optom Assoc. 68(5):305-8 (1997). (link)
  11. Schmidt, P. et al. Comparison of preschool vision screening tests as administered by licensed eye care professionals in the Vision In Preschoolers Study. Ophthalmol 111, 637-650, (2004). (link)
  12. Sanchez, I., Ortiz-Toquero, S., Martin, R. & de Juan, V. Advantages, limitations, and diagnostic accuracy of photoscreeners in early detection of amblyopia: a review. Clin Ophthalmol 10, 1365-1373, (2016). (link)
  13. Kirschen, D. & Isenberg, S. J. The effectiveness of an autorefractor with eye-tracking capability in pediatric patients. J AAPOS 18, 217-221 (2014). (link)
  14. Kulp, M. T. et al. Accuracy of Noncycloplegic Retinoscopy, Retinomax Autorefractor, and SureSight Vision Screener for Detecting Significant Refractive Errors. Invest Ophthalmol Vis Sci 55, 1378-1385 (2014). (link)
  15. Sankaridurg, P. et al. Comparison of noncycloplegic and cycloplegic autorefraction in categorizing refractive error data in children. Acta Ophthalmologica 95, e633-e640, doi:10.1111/aos.13569 (2017). (link)
  16. Logan NS, Wolffsohn JS. Role of un-correction, under-correction and over-correction of myopia as a strategy for slowing myopic progression. Clin Exp Optom. 103(2):133-137 (2020) (link)
  17. Harvey, E. M. Development and treatment of astigmatism-related amblyopia. Optom Vis Sci 86, 634-639 (2009). (link)

Leave a comment