VISION ASSESSMENT OF THE PEDIATRIC PATIENTS

Abdelmonem M. Hamed,MDProfessor of OphthalmologyBanha College of Medicine

Zakazik University

Vision testing of preverbal children

(up to 2-3 years of age)

The vision is usually evaluated by assessing visual behavior, not VA

The goal is to determine :• If the child’s vision behavior is normal for his age.• If the vision is equal between the two eyes.

Vision testing of preverbal children

Normal visual behavior of infantsAge (months) Behavior

0-1 *Turns eye & head to look at light source*Horizontal tracking (don’t assess vertical movement at this age)

2-3 *Vertical and circular tracking*Interested in mobiles

*Interested in lip reading

3-6 *Watches own hand*Reaches toward, and later grasps, hanging objects*Observes toys falling and rolling away*Shifts fixation across medline

7-10 *Notices small bread crumbs*First touches them, then develops pincer grasp*Interested in pictures

11-12 *Visual orientation at home*Looks through window and recognizes people*Recognizes pictures.

TIPS:

• The child must remains still while testing the visual behavior .• The examiner should assess both eyes together then test each eye

separately.• Testing the fixation reflex several times will improve the

accuracy.• The best fixation target up to 4th month is the human face.• A small colorful toy makes a good fixation target for children

older than 4 months of age.toys that makes noise should not be used, because the child may follow the sound, light should also be avoided (visual noise).

Documentation

Two methods are used for documenting fixation reflex results

Fix and follow(F+F)

Central-steady-maintained(CSM)

C = monocular central fixation. if eccentric fixation……….(NC)S = the child can hold (steady) fixation if not…………..…(US) unsteadyM= the strabismic child ability to maintain(M) fixation with the viewing eye when the other eye is uncovered if not maintained(NM)

It means under monocular conditions (the opposite eye is covered) the child is able to fixate on and follow target. In children with strabismus the test should be done monocular while both eyes are open

Amblyopia detectionIs the vision in two eyes are equal?• Yes…….then it is OK.• No……..amblyopia suspect.

How to know?• If the child has strabismus, it is easy to know;

– strong preference of one eye indicates the presence of amblyopia in the other eye.– The ability to alternate fixation with either eye indicates equal vision in both eyes.

• If the child has straight eyes, it is more difficult to know;– the differential occlusion test (DOO test) is helpful….while closing the

amblyopic eye it does not bothersome, but closing the sound eye makes the child cry.

– A child with equal vision in both eyes, will react proportionally when either eye is occluded or will not react at all.

– Sometimes children become agitated when approached ……unhelpful DOO test.– There are many other tests can be used as vertical prism test (VPT) and 25-prism

diopter test

• A 10-D prism is held base down ã in front of Rt. Eye vertical tropia the Lt. Eye moves up to regain fixation remove the prism, if The child switches

fixation to Rt. eye i.e. up movement of the eye Rt eye preference may be amblyopic left eye.

• Repeat the test for the Lt eye.• If the child is able to fix with both eyes (no switch), then the

vision is equal.• The 25-prism diopter test my be performed in the similar

manner.

Vertical Prism Test (VPT)

Forced Preferential Looking• The children prefer to look at the patterned alternating contrast over a homogenous target.• Applications:

– grating (Teller) acuity cards.• limitations:

– false -Ve. Due to lack of cooperation or large visual field defect.

– False +Ve., due to difficulty in assessing fixation movements specially in presence of nystagmus or abnormal ocular motility.

Grating (Teller) Acuity Cards

Vision testing in verbal children

Tips:• an accurate assessment of VA can be made in almost all

cooperative verbal children, specially who are > 3 years of age.• If child wear glasses, VA should be tested W and Wout. them.• There are many psychological tests that can be used according to

the age of the child.• Start with the the test target close to the child.• Teach the child how to do the test while both eye are open, then

test the VA monocular. If the child is known to have amblyopia in one eye, test the amblyopic eye first.

• children has a very short attention span and become disinterested quickly.

Vision testing in verbal childrenTips:• So, it is better to start W a small row…...the 6/12 line. If there is

trouble W this line……move to larger row. If the child easily reads 6/12 line………...skip to 6/9 or6/6 line.

• The child VA acuity vary W age 4-5 years old should have at least 6/9, the younger children may not be able to see better than 6/12 or 6/18. But VA should be the same in both eyes.

• Encourage the child to read.• It is not necessary for the child to get all optotypes on a line

correct, but he should identify the majority of them.• If the VA differ by more than one line between both eyes, the

amblyopia should be suspected.But the vision should be retested in the poor eye.

types of psychological tests

Vision testing in verbal children

Picture optotypessuch as Lea figures, and Allen cardsdisadvantages:• It depends on child

familiarity W the picture.• Some of them require a

verbal response.• Not able to test VA better

than 6/9, due to difficulties in constructing accurate pictures.

Matching optotypesDirectional optotypes

• Such as E game and Landolt broken rings

• Make it 3-choice test instead of 4-choice test ( up,down, or to the side) to overcome child problem of laterality.

• Use this test when the child is unable to communicate verbally, the child just points to the correct letter on a sample page containing 4 figures.

• The Lea figures, Allen cards, E game and Landolt broken rings can be used in a matching mode.

Interacting with parents

• Parents are often apprehensive during the vision testing process.

• Ask parents not to make comments such as “why can’t you see that?” “he can’t see this big letter” such statements complicate the testing process.

Avoiding test artifacts

• Peeking.• Memorization: it can be overcome if the

examiner asked the child to read the optotypes backwards.

• Crowding phenomenon: specially important in amblyopic child!

Avoiding test artifacts• Nystagmus artifact:

– Nystagmus can be manifest (present all time) or latent (present only when one eye is covered)

– Pt. with manifest nystagmus should have VA tested with both eyes opened and with each eye individually. Vision should be assessed with the child’s head erect and with the child’s head in the preferred abnormal head posture.

– For Ex. Vision tested with both eyes open With head straight………… 6/18 With head turned to left……..6/9 (at null point) the vision then tested with each eye separately

Avoiding test artifacts• Nystagmus artifact:

– Latent nystagmus, when one eye is covered, nystagmus develops and VA worsens

– Pt. with Latent nystagmus should have VA tested with both eyes opened and with each eye individually, by using a + 10.00 lens instead of an occluder or patch. This technique is known as fogging which allows monocular acuity to be more accurately assessed.

– For Ex. Both eyes open…….6/6 Right eye……….… 6/9 (+ 10.00 fogging lens) Left eye………..…..6/9 (+ 10.00 fogging lens)

Near vision testing

• Near vision is not routinely tested in the pediatric population.

• However any time there has been a decline in educational or school performance, a near vision evaluation should be performed.

• There are many near vision testing charts which are similar to distant vision testing charts.

Testing vision in children with special needs

• Such as children with cerebral palsy, mental retardation,…etc

• what is the goal of vision testing?– If the child sees.– How much he sees.

• Observations!– Of the clinical signs that indicate the possibility of

visual impairment such as:• manifest nystagmus.• Blindinism; oculodigital reflex, repetitive rocking of

the head, repetitive hand waving.

Testing the VA:– direct a bight light into the patient eye……he should close his eye and/or withdraw.

–Normal papillary light reflex.……indicate that the ant. Portion of the visual system is intact (it is normal in cases od cortical blindness).

–If the examiner rapidly moves his hand towards the patient,s eye.……the patient should withdraw--it is helpful only after 6 months.(the threat response)

Testing vision in children with special needs

Testing the VA:–the vistibulo-ocular reflex (VOR); spinning a child stimulates similunar canals in the inner ear…….nystagmusa child with normal vision will inhibit nystagmus within 3-5 seconds after body rotation has ceased, otherwise will often continue to have nystagmus for 15-30 seconds.

–Optokinitic drum; it also creates nystagmus, and the VA can be estimated (false -ve results occurs in child who lacks interest, or in a child who does not have normal ocular motor function.

–VEP; last test to order (a normal VEP may occur in absence of the functioning visual cortex).

Testing vision in children with special needs