Assessing Binocular Function in Children

Stereopsis

At birth the mechanism req. for binocular interaction is not present. At 3-4mths the binoc. cells in the cortex receive input from both the right and left eyes and gross stereo is present. This reaches adult levels at 6mths according to computerised preferential looking, w/a slower improvement in clinical tests. Sensitivity to pictorial depth info doesn't develop until after 6 months. Stereopsis is an important screening technique - loss of stereopsis can often mean development of strab/amb or blur from uncorrected refractive error. Gross stereo doesn't necessarily rule out the possibility of milder levels of amb/aniso/strab eg microtropia.

Accommodation

Newborn infants are capable of accommodation but aren't too accurate. They are fairly accurate by 3-4mths. Younger kids are fairly insensitive to blur compared w/older kids and adults.

Convergence

Appropriate vergence eye movements are found in infants below 2mths of age. The ability to maintain constant fixn (eg w/moving objects) and alter convergence over large ranges improves w/age. The response is well developed by 6mths but acc and conv systems aren't correlated until at least two months of age

Assessment of Infants

• Neonate is visually responsive
• Need to differentiate between normal and abnormal visual development
• Max info in the shortest time
• First do VA, Cover test, motility, stereo. If kid has good VA and stereo Rx not likely to be a problem
• Use appropriate tests and make it fun

INFANTS

• Simple obs. look for saccades etc
• Behavioural tests - alternate occlusion, visual cliff - stereopsis
• VA: <6mths>6mths pref looking @40cm, tracking (OKN), VEPs.
• Hirschberg - central + symmetrical. 1mm diff = 20D squint
• BV - 20D base out - eg base OUT in front of RE: eyes turn to left then LE converges - fusional movement
• Cvr test w/interesting targets and hand as occluder
• Stereopsis - LANG or Frisby if >7mths
• Ret - gross differences between eyes or large Rx, near ret, cyclo

1-2 YEARS OLD

• Cover test, motil, ret, ophthalmoscopy
• VA w/Cardiff cards prefer pref looking w/picture, vertical so better for px w/nystagmus
• Kay's Pics 18mths-3yrs

>3 YEARS OLD

• H+S, VA, motility, stereo, TNO, Frisby, Titmus
• Cyclo ret, ophthalmoscopy
• VA w/Sheridan Gardner - child points to letter, cambridge crowding cards, LogMAR crowded