TOPIC 3: PRELIMINARY AND BINOCULARITY ASSESSMENTS Flashcards
why is Preliminary and BV assessment MORE important for paediatric compared to an adult or geriatric patient?
This is because the visual system is still developing for infants and young children.
Early detection of anomalies, impacts the prognosis.
Warning signs of BV?
-Posture
-Head tilt?
-Face turn?
-Eye turn?
-Eyes rubbing?
-Closing one eye
*List are non-exhaustive
Observations to note based on paediatric age: Let’s try!
infants and toddlers:
-strabismus, tropia, comitancy
-gross anomaly
pre-school and school age:
-vergence or acommo issues
-subtle anomaly
Parent VS Optometrist: WHO to look out for WHAT?
Parent:
- eye turn when tired or when looking up
-covering or squinting 1 eye
-headache
-abnormal eye positions in diff gaze
-asymmetric lid position
-AHP
Optometrist:
-scleral signs or previous strabismus (e.g scar, localized redness)
-anatomical asymmetry, malformations or signs of injury
-epicanthus
-ptosis or other abnormal lid openings
-strabismus
-AHP
-exophthalmos
what are the 5 tests that can assess the alignment of the 2 eyes
1) Hirshberg
2) Krimsky
3) Bruckner
4) Cover Test
5) Ocular Motility
what is the objective of Hirshberg Test? what is it’s principal?
Simple and objective test to detect tropia and estimate its magnitude in non-verbal patient.
based upon the assumption that if central fixation and binocular alignment are present, the corneal reflection of a light being fixated by the patient will be in identical positions in the two eyes.
clinical procedure for Hirschberg? what is the norm?
- Shine a penlight about 50cm in front of the patient’s eyes (equally into the patient’s eyes at midline)
- Observe the displacement of the corneal reflection from the centre of the pupil
- Determine the fixating eye by observing which eye has the corneal reflection in the identical position with the angle lambda measurement (if strabismus present)
Normal eyes: Both corneal reflexes are slightly displaced nasally due to angle lambda
what will be seen in strabismic eye for hirshberg?
observe the displacement of the corneal reflection (spot of light) from the centre of the pupil.
For patients with strabismus or misalignment of the eyes, the corneal reflexes are not equally placed (asymmetry).
what is the recording for HIrshberg?
indicate the position of the corneal reflex and whether they are symmetrical.
“+” indicate nasal displacement and “−” indicate temporal displacement.
e.g:
OD: +0.50mm OS: +0.50mm OR Symmetry
how to calculate estimated amount of strabismus in Hirshberg?
A relative difference in position between the right and left eye reflexes of 1mm is approximately equal to 20∆ (prism diopters).
Eg: the reflex in the right eye is +0.5mm and the reflex in the left eye is +2.0mm, the patient would have a left exotropia of 30∆ (1.5 x 20∆).
what are the 2 types of pseudo-tropias? what kind of eyes are they commonly seen in?
Pseudo-esotropia: young children (especially Asian) with epicanthus
Pseudo-exotropia: wide-set eyes and or unequal palpebral aperture
what is krimsky?
Krimsky procedure is a modification of the Hirschberg test in an attempt to make a more accurate measurement of the amount of strabismus.
prism is used to change the position of the corneal reflection in the deviating eye.
The amount of prism needed to reposition the corneal reflection in the deviated eye to the angle lambda position is the measurement of the magnitude of the strabismus.
clinical procedure for krimsky? what is the norm?
- Penlight is held 50cm from the patient’s face in the midplane.
- Examiner observes the corneal reflection of the light in each cornea while the other eye is covered (angle lambda).
- Determines the fixating eye and places a prism bar or loose prism in front of fixating eye (aka “good” eye):
If esotropia is present, base-out (BO) prism is used.
If exotropia is present, base-in (BI) prism is used.
The amount of prism is increased until the corneal reflection in the deviated eye moves to the angle lambda position.
what is the recording for krimsky?
OD: 5^ esotropia
OS: 5^ esotropia
clinical procedure for bruckner?
Clinical Procedure:
- Dim room illumination.
- Shine penlight/direct ophthalmoscope at 1m to both eyes
- Ask the patient to look at the light with both eyes open.
- Compare the colour and brightness of the fundus reflexes.
notes fir bruckner?
Remove any spectacles that the patient may be wearing. However, if it is felt that the refractive correction will alter the result (e.g. in cases of significant hyperopia), the test should also be performed with correction.
Hold a penlight/direct ophthalmoscope horizontally 1 metre from patient with the light aimed at the bridge of patient’s nose. The back of the penlight should be very close to the tip of your nose.
what is a red flag in bruckner?
Red flag: a difference in brightness of the red reflex between 2 eyes.
Whiter or brighter pupil indicate problem eye
(with strabismus)
Crescent is seen in eyes with refractive error
Inferior crescent: Myopia
Superior crescent: Hyperopia
what age should bruckner be used for?
Test is sensitive for infants (~ 8 months old).
Less sensitive in older children due to reduced visibility with age
(Believed to be due to changes in retinal pigmentation)
LOOK AT BV NOTES FOR OMM AND CT
OK
vergence and accomo target for children <7 years old?
using of multiple and interesting target is recommended:
Toys with sounds, music, lights and variety to keep their attention is needed.
NPC norm for children? when will NPC be present?
orm: 8-10cm for all children
Note: NPC present at age 8 weeks
accommo procedure and norm for children? when will accomo be present?
Slowly move target towards child aiming for the tip of their nose.
You need to be watching their pupils to make sure you see them constrict as your finger gets closer.
Note: Response well developed at age 3-4 months
what will you see in BO prism fusion test? how many dioptres of prism should you use for <1 year old, 1-2 y/o and over 2 y/o?
Nasal movement in eye with prism (absence of suppression)
Version movement in other eye (Hering’s Law)
Re-fixating vergence movement (absence of suppression in other eye)
10D BO test (until about 1 yo)
15-20 D from 1 to 2 yo
20 D over 2 yo
Note: Possible no response until about 4 months old
norm for BO prism test?
Norm: Recovery should be fast and smooth
version then vergent movement of eye without prism
how should we conduct BV assessments for children over 7 years old
For a child aged of 7 and above, BV test can be conducted as per norm (similar to adult)
However, still important to explain in simpler terms and make it fun for the child.
4 compulsory BV tests for paeds?
Cover Test
Ocular Motility
NPC
Stereopsis
three main requirements for stereoscopic vision?
-a large binocular overlap of the visual fields
-partial decussation of the afferent visual fibres
-co-ordinated conjugate eye movements
TD for stereoscopic tests?
Most stereotest are conducted at near, usually 40 centimeters distance except frisby
where is frisby used, advantages? what kind of principal does it use?
Most commonly used in hospitals and clinics in Singapore for young children - No additional eyewear or filters needed + allows for accurate stereo assessment.
Random dot
Real thickness - 3 square plates of variable thickness 6mm, 3mm, 1.5mm
testing distance and Stereoacuity range for frisby?
Testing distances - Variable (30 - 80cm)
Stereoacuity range: 600 sec (6 mm plate at 30 cm) to 20 sec (1.5 mm plate at 80 cm)
procedure for frisby? recording?
Patient should view the presented plates squarely (no tilting or turning of head)
Plates should be placed against the white background of the Frisby Test box.
Measure testing distance (test can be held at any of six distances, from 30cm to 80cm) and ask patient to decide in which pattern the hidden circle is.
For the tester to identify the stereoscopic square in order to verify the subject’s answers, discreetly touch the studs on each corner of the plate. On the stud nearest the correct square is a small flattened area, easily felt, but invisible to the subject.
Record stereoacuity accordingly.
Record the stereoacuity as ‘at least’ the highest level if testing was at 40 cm and the responses were all correct, e.g. Frisby≤85”
where is Lang used, advantages? what kind of principal does it use?
designed to simplify stereopsis screening in children. It only assesses gross stereopsis.
This is a useful test to have available as it is easy to use, does not require goggles, provides valuable information and is relatively inexpensive.
principal: Random dot and cylinder gratings
testing distance and Stereoacuity range for lang?
Testing distances - 40cm
Stereoacuity range: 1200 to 200 sec of arc
procedure for lang? recording?
- Hold the card at a distance of 40cm from the child
- The star can be seen monocularly to help attract the attention of young children.
- Ask the child what they can see.
Recording:
Test 1: cat (1200 sec), star (600 sec) and car (550 sec)
Test 2: elephant (600 sec), car (400 sec) and moon and star (200 sec)
positive or negative responses to the shapes.
For example, if elephant (600”) was seen/pointed to but not the car (400”), record as: Lang 400”–600” (Elephant +ve, car –ve).
3 ways to use lang in pre-verbal children?
For Pre-verbal children
-Encouraged to respond by reaching for the images and this action can be used to indicate that some stereopsis is present.
-Matching game; if the child cannot name the targets they see but can match them with the same targets shown on paper.
This is a good indication that stereopsis is present.
-Preferential-looking procedure can also be adopted: involves comparing the child’s fixation when the card is held in the normal fashion as compared to when it is rotated by 90 degrees.
principal, TD and stereoacuity range for TNO?
This test works using a random-dot principle and red-green goggles.
Random dot used with R/G googles or spectacle
Testing distances - 40cm
Stereoacuity range: 480 to 15 sec of arc
procedure for TNO? recording?
- Explain the test to the patient: ‘I am now going to test your 3-D vision.’ Place the red–green goggles over the patient’s habitual correction.
- Hold the booklet at about 40cm, angled so that it is parallel to the plane of the patient’s face.
- Keep the room lights on.
- For a general screening test, the first four plates are useful as the disparity is large and provides a qualitative assessment of stereopsis. If the patient has a short attention span it is advisable to present Plate III alone as this gives a good early qualitative indication if stereopsis is present. Find out if the images can be seen:
explain plates 1-7 of TNO
Plate I: two butterflies, one can be seen monocularly, whereas the other can only be seen if stereopsis is present. Ask the patient: ‘How many butterflies can you find on this page? Can you point to them?’
Plate II: There are four discs. Two may be seen without stereopsis. Ask the patient: ‘How many circles? Which is the biggest?’
Plate III: Four ‘hidden’ shapes (circle, square, triangle, and diamond) are arranged around a central cross that is visible without stereopsis.
Ask the patient: ‘Can you find a cross/square/triangle/circle/diamond? Can you point to it?’
This plate is very useful with children, as they like to find and name shapes. You will need to remember the correct locations of the shapes in order to verify the accuracy of the responses.
Plate IV: This is a suppression test. There are three discs. When viewed through the goggles, one disc is seen only with the right eye, one is seen only by the left eye, and one seen binocularly. Ask the patient: ‘How many circles can you see on this page? Can you point to them?’
To quantitatively measure stereopsis, proceed to plates V to VII.
Plates V to VII: These plates present images that present disparities from 480 to 15 seconds of arc. At each disparity level, two discs with a sector missing are presented in different orientations (Figure 6.19). Using the demonstration on the left of the display, ask the patient: ‘In each of these squares there is a cake with a piece missing. Can you find the cake and point to the piece that is missing?’
recording for TNO?
If the stereo shapes are identified in
Plates I–III but not V–VII, record ‘Gross Stereopsis;
TNO Plates I–III correct’. If Plate IV is incorrect, record which eye is being suppressed.
For Plates V–VII, record the stereoacuity as ‘at least’ the highest level where both responses were correct e.g., ‘TNO stereoacuity ≤15”.
Plates I – III: establish presence of stereoscopic vision
Plates V – VII: determination of stereoscopic sensitivity
what should we do if px takes a while to respond to plates in TNO?
If the patient is hesitant about an answer, allow them time to view the test plate.
If only one of the two tests for each stereo level is called correctly, allow them a second attempt at the incorrect one, but if called incorrectly again, or if the patient does not volunteer an answer, record the result as the previous correctly identified stereo level.
In patients achieving a poor test result, it can be useful to repeat the test with the red–green goggles reversed to ensure an accurate assessment of stereoacuity.
what is the use of randot stereogram? what is the stereoacuity range?
Randot Stereogram
Gross stereopsis evaluation using six geometric forms
(500 & 250 seconds of arc)
Graded circle test (400 to 20 seconds of arc)
what is the use of fly stereogram? what is the stereoacuity range?
Gross stereopsis (355 to 700 seconds of arc)
Graded circle test (800 to 40 seconds of arc)
Animal test for children (400 to 100 seconds of arc)
what is the use of butterfly stereogram? what is the stereoacuity range?
Gross stereopsis (2500 to 1200 seconds of arc)
Graded circle test (800 to 40 seconds of arc)
Animal test for children (400 to 100 seconds of arc)
3 yo and above
age group for colour vision made easy? diff between CVME and ishihara?
Test children as young as 3 years old!
It is made of shapes and pictures instead of numbers as seen in Ishihara.
one demonstration plate and 9 test plates displaying circle, star, and/or square throughout the plates and can be completed in under 60 seconds.
TD and the 3 method of performing CVME
Testing distance: 60-75cm
methods of performing this assessment:
1) Naming
Child to name the shape of picture seen
Example: Square
2) Tracing
Child to trace the shape or picture seen using cotton bud*
*A reminder the coloured pages should not be touched
3) Pointing
Child to point to the shape or picture mentioned by examiner
Example: Top, Down, Right, Left
