Physicians finessing the pediatric eye examination

Reviewed by Jeff Locke MSc, OC (C), COMT

According to Jeff Locke, MSc, OC(C), COMT, former co-chair of the Canadian Orthoptic Society, the pediatric eye exam can be improved with several small steps.

Locke, an orthoptist/instructor and team leader in IWK Health’s Visual Electrophysiology Laboratory in Halifax, Nova Scotia, Canada, discussed the issue of refining pediatric eye exams.

“We can streamline things and make the study 1% better by being more competent at assessing visual acuity, checking for binocular single vision, and by knowing what visual electrophysiology can do in this age group,” Locke said.

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For vision to be normal, stimuli must travel through our optics to the retina, the retina to the optic nerve, and the optic nerve to the cortex.

“Acuity can be based on which aspects of the pathway are stimulated,” explains Locke.

To benchmark 20/20 vision in a baby, the test types and the visual acuity to be measured must be changed, Locke said.

“We need to switch to more detection-based acuity versus recognition,” he said.

In pre-verbal children, forced choice preferential viewing (FPL) tests like Cardiff and Teller aren’t the most accurate at detecting and managing amblyopia, he stressed.

Locke noted that it’s easy to get complacent with FPL tests and stop documenting those previously learned tests.

As a child achieves more visual milestones as they age from newborn to 1 year, the doctor may perform more complex tests.

Related: The Challenges of Examining Visual Fields in Children

“It does not mean that those tests taken during previous milestones are [when a child was younger] are no longer useful,” he explained. “They can add great qualitative aspects to your vision examination.”

Indeed, vision testing in infants should have more qualitative than quantitative assessments, Locke said.

A quantitative test like the FPL test serves as a measure of normal vision in infants and provides a value over time, he noted. That said, qualitative tests are quick to perform and can help detect asymmetry in vision, Locke said.

In terms of visual assessment tests, Locke pointed to research showing that optokinetic nystagmus induction methods are suboptimal in determining visual acuity thresholds.

He noted that they can be a good qualitative indicator of the visual pathway, as intact pursuit and saccadic centers are required, as well as normal cranial nerve innervation to the extraocular muscles.1

Related: Looking to the Future of Pediatric Ophthalmology

More recent research2 has suggested a strategy for a pediatric visual acuity study, Locke noted.

“[The study authors] advised for best compliance to start with binocular visual acuity with Cardiff at 50cm, followed by induced tropia,” Locke said. “Once these are successfully completed, you can try monocular visual acuity at 50cm with your FPL Cardiff [test]. Their vision was to assess both FPL Cardiff at 50cm and induced tropia provides a more accurate visual assessment and allows practitioners to gain more information if they lose cooperation [from the pediatric patient].”

An informed assumption is made based on observational data and detection-based acuity with pediatric studies, Locke noted.

“If we try to make a comparison between detection-type acuity, such as forced choice preference, we’re probably overestimating the acuity, and it becomes challenging to detect mild to moderate levels of amblyopia,” he said. “Each detection type of acuity has demonstrated validity in assessing the pediatric population, but sensitivity in detecting amblyopia varies between tests. None seem as robust as crowding-based testing.”

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The goal should be to maximize visual examination by combining multiple methods of detection-based testing, not only to increase sensitivity, but also to gain more general, ocular health knowledge from the pediatric patient, Locke explained.

“Do as much as you can with binoculars” [assessment] while the child is comfortable with you, but at the same time you are extracting data,” he said.

The result of the FPL test should not be the only endpoint in an assessment of children’s vision, Locke emphasized.

“Make your exam 1% better by adding a qualitative measure to the mix,” he said.

And for those not using the FPL test, Locke recommended establishing a clinic-wide grading standard for fixation testing to help track amblyopia over time, noting that children don’t need to be old enough to verbally respond before assessing binocularity.

However, there are some objective methods that are used to get a sense of binoculars.

Related: It Takes A Village To Beat Children’s Visual System Diseases

“We can test motor fusion ability in infants and newer studies are coming up using the FPL test in stereopsis,” he said.

Detecting stereopsis will help guide a care plan and add confidence to visual acuity assessment, Locke noted.

The challenge with visual electrophysiology in pediatrics is that most tests require a baby or toddler being assessed to work together to obtain accurate results, making the tests not always practical, with the exception of the electroretinogram (ERG), which can be done under sedation, Locke said.

“The ERG is our bread and butter, but they can’t pinpoint the dysfunction specifically to the macula,” he said.

Visual evoked potentials (VEPs) provide an objective measure to the cortex, but anomalies at any level of the optical pathway (optic, macula, optic nerve, optic pathway) can lead to VEP pathology, Locke noted.

Another clinical gem he offered is that assessors avoid turning their backs on their pediatric patients.

Locke suggested placing the computer screen where information is entered so as to maintain a view of the assessed child.

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Jeff Locke MSc, OC (C), COMT
p: 902-470-8888
This article is based on a presentation at the Virtual 31st Annual Jack Crawford Day Pediatric Ophthalmology Update. Locke has no financial information related to this content.


REFERENCES

1. Kutschke PJ. Preverbal assessment for amblyopia. Am Orthopt J. 2005;55:53-61. doi: 10.3368/aoj.55.1.53

2. Nanda KD, Blaha B, Churchfield WT, Fulwylie CR, Medsinge A, Nischal KK. Induced tropia test and visual acuity testing in nonverbal children. J Binocul Fish Ocul Motil. 2018;68(4):134-136. doi:10.1080/2576117X.2018.1525235

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