Examination Sequence

The following examination sequence was adapted in part from the AOA Clinical Practice Guidelines and also meets the Vision Service Plan (VSP) guidelines for an infant/toddler examination.  (Of note, VSP only allows this examination to be billed at an intermediate level.)

1. History
2. Fixation preference testing
3. Extra-Ocular Muscle assessment (EOM)
4. Near Point of Convergence (NPC)
5. Cover Test or Hirschberg & Kappa tests & Brückner test
6. Confrontation Visual Field (OU)
7. Near Retinoscopy
8. Forced Preferential Looking Test (< 1yr: Teller Acuity Cards, >1 yr: Cardiff Acuity Card)
9. Anterior segment evaluation & Pupils assessment
10. Cycloplegic retinoscopy (2 drops of 0.5% cyclopentolate 5 minutes apart for infants < 1 year)
11. Posterior segment evaluation

1.  History

Like any routine examination the first information collected is the chief complaint, so the same mnemonic of Frequency, Onset, Location, Duration, Associated factors, and Relieving factors will apply.  Typical reasons for an infant eye examination may be: an eye turn (constant/intermittent), red / watery eyes, or an infant that makes poor eye contact.  An intermittent eye turn before the age of 4-months old may be present secondary to immature binocular vision.  Research has shown a spike in binocular development occurring approximately between 4-6 months of age.  Another common reason that a parent may bring their child in for an eye exam is the presence of an eye turn.  In these cases, it is the responsibility of the examiner to differentiate an actual strabismus from a pseudo-strabismus.  A pseudo-esotropia may appear secondary to prominent epicanthal folds, the skin between the eyes.  If the epicanthal folds occlude a portion of the nasal sclera, the eyes may appear esotropic, when in fact they are aligned.  This is especially the case if there is an asymmetry in the amount of nasal sclera that is covered in each eye.  Chronic red and watery eyes may be a sign of Nasolacrimal Duct Obstruction (NLD), this should not be confused with infantile glaucoma which also presents with red and watery eyes but also has an associated photophobia.  The differentiation between NLD and an acute bacterial conjunctivitis will be the onset.  Adoption of unusual head postures, poor eye contact and fixation, excessive blinking, unusually close working distances, as well as squinting should also raise some concern for uncorrected refractive error or other reasons for reduced acuity.

Eye and medical history will most likely be minimal at this point.  Medical history will be important to note pre-, intra-, and post-natal history.  Of note within prenatal history, babies from high risk pregnancies have a higher incidence of certain vision conditions.  In-vitro fertilization has been found to been associated with ocular conditions such as retinoblastoma, Coat's Disease, congenital cataract, and microphthalmos.  A key postnatal history question would be the APGAR score (Activity, Pulse, Grimace, Appearance, Respiration), which is taken after 1 minute and 5 minutes of delivery.  A score of 8 or greater is usually considered healthy.  A premature infant is any infant born before 37 weeks gestation and low birth weight is defined as <2500 grams (~5.5 lbs).  Prematurity is a significant historical finding as premature children have a higher prevalence of myopia and astigmatism, and if birth weight is below 1500 grams (~3 lbs) they were at risk for developing Retinopathy of Prematurity (ROP).  Developmental history is also important to know as it may provide insight into signs of congenital malformations and neurological disorders.

Family eye and medical history may have more robust information and provide better insight into possible concerns for what to watch out for since there are numerous conditions that appear to have hereditary components such as strabismus, amblyopia, refractive error, and select ocular diseases.

2.  Fixation Preference Test

This test was originally designed to screen for amblyopia in a strabismic infant.  The rationale of the test was that an infant would choose to fixate with the "better seeing eye", so if amblyopia existed, the infant would not fixate with the amblyopic eye or would only fixate momentarily.  In an infant that does not appear strabismic, the same test can be done to qualitatively assess if the vision in the right and left eye are fairly equal. 

1. Begin by dissociating the child with a 10^Δ; base down prism in front of the right eye and have the infant fixate on an age appropriate target. 
2. The infant should now be seeing double, with the image seen by the right eye is above the image seen by the left eye.

3. The examiner then occludes one eye to force fixation with the unoccluded eye. 
4. If a child responds negatively when one eye is occluded, this may be an indication that the acuity in the unoccluded eye is not as good as the other eye.  To test that hypothesis occlude the other eye and observe any differences in behavior.
5. Upon unocclusion observe the fixation pattern.  Did the infant maintain fixation with the previously unoccluded eye? Or did the child immediately re-fixate with the eye that was previously occluded.
6. Repeat procedures 3-5 with the other eye.
7. If an abnormal response was found, the abnormally fixating eye is suspected to have at least a 3 lines worse acuity as compared to the preferred eye.  Refer to the visual demonstration piece at the end of this lecture.

Sample Question: You are performing fixation preference testing on a 7-month old boy with a 10 BD prism in front of the right eye and observe no spontaneous alternation of the eyes.  You then cover the right eye, the left eye does not move, and upon taking away the occluder the left eye still does not move.  Upon occlusion of the left eye, the right eye moves up.  When the occluder is removed, the right eye immediately moves down.  What do these results mean?

Answer: The right eye is suspicious for at least a 3 line reduction in acuity as compared to the left eye

3.  Extra-ocular Muscle Testing (EOM)

EOM testing can be accomplished by slowly moving an age appropriate (brightly colored, illuminating, and preferably makes noise) toy in all 9 fields of gaze.  A mother's face may also be an appropriate target.  If a child refuses to follow the target, an oculocephalic reflex (Doll's Head) can also be done.  This involves having the patient maintain fixation on the examiner or the parent's face and moving the infants head away from the field of gaze of interest.  For example, to assess right gaze (right lateral rectus and left medial rectus muscles), the examiner would turn the infants head towards the patient's left.

4.  Near Point of Convergence (NPC)

Gross convergence ability develops to almost adult levels by 3-4 months of age, and fusional vergence can typically be demonstrated in infants by 6-months of age.  To test convergence, the examiner can set the transilluminator/penlight directly in front of the infant and move in towards the infant.  Since the infant will not be able to verbally indicate when there is a break in binocular fixation, monitor the corneal reflexes.  The moment there is a change in reflex location in either eye, will indicate the break point.  As the examiner proceeds to retreat with the transilluminator/penlight a refixation indicates recovery of binocular fixation.