by Michael J. Earley, OD, PhD and Marjean Taylor Kulp, OD, MS
Currently, under the Affordable Care Act, a yearly comprehensive eye exam for all children under 18 years old is defined as an “Essential Benefit”. This provides optometry with a tremendous opportunity to truly make a significant impact in the lives of these children. Kids coming in for comprehensive vision exams provide an essential opportunity to identify children who have significant vision problems which may impact their performance in school and/or sports, and subsequently their overall self esteem. Of course, this gain cannot be achieved unless the testing performed at the vision exam is sufficient to uncover the visual conditions that can serve as barriers to success. We are all aware of testing that constitutes a “comprehensive exam”. Below are six essential tests (yes – essential testing for the essential benefit) that should be completed on ALL children who are seen for comprehensive vision exams. This list is not intended to be exhaustive and certainly many other tests could be added. Our goal is to show that running a few simple tests ACCURATELY can make a big difference in identifying versus missing a visual issue in your pediatric patients. Simply performing these tests is, of course, not enough. You have to follow up on treatment or make the appropriate referral if a child does show deficits on these tests. A complete sensorimotor examination should be recommended for children with suspected binocular vision problems.
Tests that may be done by a technician or doctor depending on practice flow:
1. Symptom Survey
Children are terrible historians and do not typically enter the exam room with a chief complaint in mind. Myopes who currently wear glasses will tell you that “far away is not as clear as it was”. Kids with binocular vision problems, however, will not typically present with “I suffer from asthenopia after 25 minutes of sustained near work.” They often don’t realize that the symptoms with near work (e.g. headache) are secondary to a vision problem. Therefore, we have to directly ask about specific symptoms to elicit a significant finding. The Convergence Insufficiency Symptom Survey (CISS) is one possible survey that can be a useful tool to help identify kids ages 9 and up with significant near work symptoms. It has been extensively studied and validated in clinical trials and is extremely easy to use. Normal children without binocular vision or accommodative problems have an average score of 9 on the CISS. A reliable cut-off to indicate symptomatic convergence insufficiency is a score of 16 or more. It is important to run the survey as directed (i.e. with lapcard answer key, reading questions verbatim, and limiting patient to responses on card). Download Form: CISS Form
2. Visual Acuity
Snellen acuity is fine for older kids but single, crowded LEA symbols or HOTV should be used in young children. Single optotypes with crowding bars have been shown to be effective in identifying amblyopia and to give more repeatable outcomes. Optotypes that do not blur out equally, such as Allen Figures, should be avoided. A lap card which shows the optotype choices is essential to improve testability in young children because the child can point to(match) or name the symbol. Studies have shown that 99% of 3-year-old children can complete visual acuity testing when using LEA or HOTV and a lap card.
With young kids, do not use a cover paddle to occlude when testing acuity. Instead use an adhesive occlusive patch or Blenderm tape when testing acuity and watch carefully for peaking. Amblyopic children are experts at peaking and will often try to peak because they want to do well for you. Many clinicians have missed decreased acuity in one eye due to a transient subtle head turn around the cover paddle. Kids think the goal is to get the letters right – not to individually test the resolution limitations of the two eyes independently!
Remember that kids often remember letters that have been presented so letters/symbols should be changed between presentations (e.g. right and left eye) or have the child read the optotypes in a different order (e.g. backwards) when testing the second eye if you are unable to change the letters/symbols on your chart.
NEVER EVER put decreased monocular acuity off to amblyopia in the absence of a TRUE amblyogenic factor. Always order necessary tests and/or make appropriate referrals to rule out other underlying causes.
3. Motor/Sensory Fusion – As in the other categories, not all tests are equally effective so it’s essential to use a test that young children can complete and that performs well in identifying children with problems.
Near Point of Convergence (NPC) is another easy quick test that can be very diagnostic IF performed correctly. It’s important to use an ACCOMMODATIVE target (e.g. a fixation stick with a vertical row of 20/30 letters) and to bring the target SLOWLY towards the child (1-2cm/second) in order to make sure the child has time to let you know as soon as he/she sees double. It’s also important to WATCH for either eye to turn out; if a loss of fusion is seen that should be recorded as the break value. Many kids with intermittent strabismus will suppress when their tropia manifests, therefore they may never report that the target doubles. A normal NPC should be closer than 6cm. A NPC break of 5.75cm or beyond has been shown to have a sensitivity of 87% and specificity of 67% for identifying school-aged children with convergence insufficiency or binocular dysfunction. Yes, this quick, simple test, when run as stated above, can help pick up most kids with CI with a low false positive outcome.
Random Dot Stereoacuity is a quick, easy test for preschool children. Testability is excellent and children generally have fun with this test. Effective tests include the Preschool Assessment of Stereopsis with a Smile(PASS) or the Randot Preschool. The PASS can be run like a hide and seek game (find smiley!) and the Preschool Randot can be run in a matching fashion. It is important to use one of these random dot tests (you can’t see the picture without the Polarized glasses) because reduced performance on these tests has been shown to be associated with significant vision problems (e.g. strabismus, amblyopia, significant refractive error) in preschool children. Tests that do not have random dot shapes such as Stereofly should be avoided. Subnormal performance is achieving worse than 400” for 3-year-olds and achieving worse than 200” for 4- to 5-year-olds on the Randot Preschool or achieving worse than 120” on the PASS.
Tests that should be done by a doctor:
In kids, retinoscopy is not just a test to “get close to Rx”, it often determines the Rx. At the child’s initial exam, determination of refractive error should include cycloplegia with cyclopentolate (we use 1% cyclopentolate/1% tropicamide) after all near testing is complete. Uncovering the full amount of hyperopia will play an important role in deciding how to treat any other binocular vision issue that is uncovered. Very young children should typically be hyperopic with at most a low amount of astigmatism. Emmetropization causes this hyperopia to decrease rapidly in the first year of life and then gradually over the next few years. An average refractive error for a preschool child is +1.25. A general rule of thumb that we use is that if a child is still 3D hyperopic at 3 years of age, then the process of emmetropization did not work and the child will typically stay hyperopic. This rule of thumb comes in handy when a parent asks if the child will always need glasses.
5. Ocular Alignment
Cover test is essential to identify any strabismus or significant phoria, however, again this is a test that MUST be run accurately to have any value. The cover should be held over each eye for 2-3 seconds on unilateral cover testing and for 1 second on alternate cover testing. It is ESSENTIAL to use prism neutralization and a small accommodative target for testing (e.g. 20/30 target or a target just above threshold for the patient). For example, a patient with convergence excess will typically try to focus slightly behind the target (lag of accommodation). With a 20/200 near target, the patient can have a lag of over a full diopter and still “see” the letter. This can cause you to underestimate the near esophoria by 10 or more prism diopters! To maintain attention, engage the child by asking questions about the target and change the target if the child loses interest. It generally takes about 20 seconds for the phoria to reach a stable position on cover testing (e.g. to find the prism which results in SUSTAINED reversal [5 reversals]). Binocular vision problems often result in significant symptoms; your patient deserves that minute of your time to do cover testing!
Use an interesting target and watch carefully for any over action or restriction. A number of binocular issues only present in secondary/tertiary gaze positions and show alignment in primary gaze.
6. Ocular Health
Ocular health assessment in a child is the same as an adult, including a dilated fundus examination. One important point to always remember is that amblyopia is not typically associated with an afferent pupillary defect so an APD requires follow up.
Again, this list is not intended to be exhaustive. It is meant to remind all of us that spending a few extra minutes running these tests accurately can greatly change the lives of many children. Amblyopia is of course a condition that MUST be detected and treated. Other binocular issues like CI, CE, accommodative issues, etc. DO have significant impacts on educational success. A COMPREHENSIVE vision exam is the essential benefit because the federal legislature was convinced that these issues need to be uncovered and treated early on in a child’s educational life. They have done their part – now we have the responsibility and opportunity to do ours!