At the completion of this article, the reader should be able to…
- Understand that while prevalence rates are debated, true accommodative dysfunction is uncommon in children who have good visual acuity and are otherwise healthy.
- Integrate a child’s aesthenopic complaints into the context of their overall ocular and general health, including identifying any differences in symptoms between their recreational habits and compulsory tasks.
- Identify limitations, difficulties, and pitfalls in diagnosing accommodative defects in children.
- Educate patients and caregivers that measures of accommodation can be unreliable and often improve without treatment, making observation and monitoring an appropriate initial course of action.
Dr Maree Flaherty
MBBS (Hons), FRANZCO, FRACS, FRCOphth
Clinical senior lecturer, Discipline of Ophthalmology, Sydney Medical School, University of Sydney
Director, Children’s Eye Centre, Wentworthville, Sydney
Jess Crippa
BAppSci(Orthoptics), Dip Business, Cert IV Health Administration
Practice manager, Children’s Eye Centre
Practitioner teacher in orthoptics, University of Technology Sydney
Member of Orthoptics Australia
Registered with Australian Orthoptic Board
Irina Sim
BAppSci(Orthoptics)Hons, MTS
Head orthoptist at the Children’s Eye Centre
Member of Orthoptics Australia
Registered with Australian Orthoptic Board
For any optometrist assessing accommodative disorders in paediatric patients, the goal is to avoid overdiagnosis and overtreatment. The authors provide critical insights into the latest evidence, highlight common diagnostic pitfalls, and offer a practical, conservative approach.
Children often complain of symptoms which might be caused by accommodation defects, however accommodative disorders are uncommon in children who have good visual acuity and are otherwise healthy. There are pitfalls associated with assessing and diagnosing accommodative disorders in children of which clinicians should be aware. The prescription of low plus lenses (with or without a bifocal) and other treatments should only be carried out when there is confidence that these interventions would be beneficial.
Pitfall 1: Validity of presenting symptoms
An Australian study showed 82% of young children who reported eye strain symptoms had normal eye examinations.1 This questions the validity of treating conditions such as accommodative disorders on the basis of symptoms alone. Many children enjoy playing handheld games, which requires convergence, accommodation and higher order visual processing skills for prolonged periods of time. It would be anticipated that children would reject this activity if a significant accommodative defect were present.2 It is therefore important to take a thorough history to determine whether a child is rejecting a particular task such as homework, or whether the reluctance relates to all near activities including the use of digital devices for leisure. This comparison can be helpful to explain to parents that eye functions are in fact normal.
Pitfall 2: Variable parameters and a lack of normative data
Scheimann reported an incidence of 2% for accommodative insufficiency and 1.2% for accommodative infacility in a clinical paediatric population,3 but multiple publications have noted a lack of consensus in the literature about the prevalence and diagnostic criteria of accommodative dysfunction.4-12 This is due to differing study designs, with significant variations in techniques of testing and measurement, and variability between age groups.
Accommodative amplitude
Accommodative amplitude (AA) can vary depending on what method is used, such as the push up or
pull away methods, minus lens, or dynamic retinoscopy.6, 11, 13-15 The push up method appears to produce comparatively higher values than both the minus lens technique13 and dynamic retinoscopy.11 There is also variation when monocular and binocular results are compared whereby monocular results are lower.16, 17 However, the value of testing AA monocularly is unclear as this does not reflect naturalistic conditions and hence the decision to treat should not be made on this basis alone.
Hofstetter (1950) estimated that the probable accommodative amplitude of a 10-year-old child was 15.5 D (with a range of 12.5 D to 21.0 D).18 This was confirmed in a recent study which showed that the median accommodation of a 10-year-old child was also 15.50 D.11 With such amplitudes in reserve, the prescription of low plus lenses and near adds should rarely be required for children.
Accommodative insufficiency
Accommodative insufficiency (AI) has traditionally been defined as an amplitude of accommodation consistently less than the level expected for the patient’s age.5, 7, 19, 20 Some would add further criteria to a reduced AA, including a low positive relative accommodation (PRA) value, reduced monocular accommodative facility (MAF) or binocular accommodative facility (BAF) or an increased accommodative lag on monocular estimation method (MEM) dynamic retinoscopy.3, 7 Others would add the presence of visual symptoms for a diagnosis of AI.20, 21 Hence, the diagnosis of AI depends on what (and how many) criteria are used, which in turn will affect prevalence rates.
Accommodative facility
There is little agreement as to what constitutes normal accommodative facility (AF) and how to test for it.22 The expected mean values to diagnose accommodative infacility (AIN) are known to vary between different age groups and be consistently lower in children than in adults.6, 23 Results may also depend on which lens flipper power is used (ranging from +/- 1.0 D to +/-2.5 D). Suggested normative values for monocular AF can vary from an ‘unrealistic high’ of 20 cycles per minute (cpm) down to 2 to 4cpm.22 Researchers have suggested the variability between the age groups is due to a lack of comprehension and lack of automatic naming of numbers (particularly of the younger age group) rather than reflecting accommodative ability.23
Adler et al noted the detection rate of accommodation infacility was 16.2% using pass criteria of MAF ≥11cpm and BAF ≥8 cpm, compared to 3.6% with pass criteria of MAF ≥6cpm and BAF ≥3cpm.24 Hence, what is arbitrarily chosen as the cut-off values for AF have a significant impact as to the number of children diagnosed with AIN and then subsequently recommended for treatment.
Accommodative lag
Accommodative lag occurs when the accommodation response is less than the demand. However, comparison between results is difficult due to a lack of agreement regarding how accommodative lag is assessed.25, 26 Additionally, accommodative lag has been reported to be quite variable in normal populations.27
It can be seen that the definition of normal will influence whether subjects are considered to have an accommodative disorder. The higher the pass criteria the more likely children are to fail the test which can inflate detection rates. Additionally, with ill-defined pass/fail criteria, it is difficult to determine the success of treatment in children that do have accommodative disorders.
Pitfall 3: Poor repeatability of accommodative ability, even in a normal population
Repeated testing of accommodation can produce variable results, and discrepancies in measurement techniques may lead to inaccuracies in diagnosis.6, 28
In a study of 137 children (four to 12 years), Adler et al found substantial intra-individual variation of accommodative amplitude measurements between initial and subsequent tests, even without any intervening therapy.29 Measurements of accommodative facility using +/- 2.0 D flippers on three separate occasions found that the vast majority of children who exhibited reduced AF values on initial testing improved to normal on repeated testing. This improvement occurred in the second minute session or on a subsequent test occasion, without any intervention.24
This variability in findings represents a barrier in identifying those who need treatment and if variations in AA and AF need to be treated at all. So it may be wise to ask the child to return for retesting to determine whether responses are consistently below expected ranges before consideration of treatment.
Pitfall 4: Accommodation testing relies on subjective responses
A major weakness in the assessment of a child’s accommodation is the examiner’s reliance on subjective responses with little or no objective information. The cooperation as well as the effort and level of attention required to accommodate under testing conditions can vary greatly, and performance is influenced by many factors including, but not limited to, fatigue, hunger, illness, mood, stress and motivation. Cognitive factors may play a role in younger children in recognising letters and understanding the instructions given.24 A study by Sheimann et al found that 31% of six year olds and 30% of seven year olds were not able to respond to binocular AF testing. At nine years of age, 10% were still not able to perform the test, which led the authors to question the reliability of testing accommodative facility in children.23 Hence, wherever possible further data, such as behavioural patterns around devices, and associated symptoms such as red and watery eyes, should be correlated to subjective responses.
Pitfall 5: Examiner influence
Another important factor in the accommodative response is the quality of instruction given. Horwood found that the most effective exercise to improve both accommodation and convergence was simple convergence exercises, but that even more effective was ‘just being encouraged to work harder by an enthusiastic tester’ – indicating the importance of therapist instructions and encouragement.27
Tester identity can also be highly significant, whereby children examined by a particular tester will score higher than with other testers.24, 29 This suggests that variations in communication and procedural explanations, the level of enthusiasm and encouragement by the tester, the technique of testing, and the interpretation of patient responses can influence the outcome of accommodation testing, particularly in children.
Additionally, there may be a response bias, in that children may wish to please by giving the answer they think the examiner wants to hear.21 Clinicians should be aware of the influence they have when testing a child’s accommodation.
Pitfall 6: Flaws in studies
Early studies cited as evidence for the efficacy of treating accommodation dysfunction in relieving aesthenopic symptoms suffered significant methodological limitations.30 These included very small sample sizes, ranging from three to five patients31-33 up to 19 patients.19, 34-36 In other studies, details about the training program were either not mentioned37 or had significant variability with the type or duration of treatment administered occurring within the one study.38-41 Examiners had difficulty assessing compliance with training32, 35 or there was an over-reliance on subjective symptoms with little quantitative values.37, 39, 42 Additionally, the earlier studies lacked either a placebo or control group19, 20, 31, 34, 35, 37-40, 42 or had an extremely small control group of one to three subjects,32, 33, 43 or had unmasked examiners.35-38, 40 Statistical analysis was also lacking in the early studies.34, 35, 37, 39
The first large scale randomised clinical trial of children (nine to 17 years) with symptomatic convergence insufficiency (CI) was initiated in 2008 by Scheiman et al with the Convergence Insufficiency Treatment Trial (CITT). 44 Out of the 221 enrolled in the trial, 164 subjects were reported to have accommodative dysfunction.45
The children were randomised into four different treatment protocols for 12 weeks and upon conclusion the authors found significant improvements in accommodative facility in all groups including the placebo group. Of the placebo group, 35.7% no longer had reduced accommodative amplitudes, and 57.7% no longer had accommodative infacility at study completion.
Therefore, the only large, randomised study to date showed that placebo treatment alone was sufficient to bring a third to a half of subjects to within a normal range of accommodative function.45 These results would support a conservative approach with active treatment delayed until if and when results are repeatedly below expected values.
Pitfall 7: Testing conditions do not correlate to naturalistic conditions
The relevance of some aspects of accommodation testing and the subsequent difficulties in measuring any significant change with treatment needs to be considered. The assessment of how quickly a subject can overcome a +2.0 D/-2.0 D flipper lens in one minute does not correlate to any naturalistic binocular condition. While accommodative function is often tested and treated monocularly, children do not focus monocularly in routine day to day activities.
Conclusion
Prevalence rates of accommodative dysfunction in children are debatable due to a lack of consensus regarding diagnostic criteria and intra-individual reproducibility, but are thought to be very low, especially in children with normal visual acuity and good general health.
The roles of motivation (both subject and clinician) and practice are difficult to isolate and control but should be considered as potentially confounding. Studies frequently emphasise symptomatic improvement as a marker of success but self-reported symptoms in children are inherently unreliable.
Clinicians should interpret symptoms, especially if they are variable or lack any objective correlate, with caution. Indicative gains may be owing to placebo effects, with or without quantitative gains. Most significantly, evidence in the literature is lacking with only one large, prospective, randomised clinical trial demonstrating that although subjects improved with treatment, placebo alone was sufficient to bring accommodation back to within normal ranges in many participants. The discerning clinician should consider all the above factors prior to embarking on a treatment plan.
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