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Visual acuity in infants

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This document discusses methods of measuring visual acuity in infants. It describes that visual acuity improves rapidly in the first years of life and matures around 5-6 years old. Several tests are mentioned, including optokinetic nystagmus testing, preferential looking tests, visually evoked responses, Cardiff acuity card tests, and observation of fixation behavior. Normal visual development milestones from birth to age 5 are provided. The document gives details on different visual acuity tests used with infants, such as the optokinetic nystagmus test, preferential looking test, and Lea paddle test.

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VISUAL ACUITY IN INFANTS Zarin khan B.Optom
VISUAL ACUITY  It is the resolving power of the eye. It is an ability to see two separate object as separate.
VISUAL ACUITY IN INFANTS  Visual acuity, in preverbal infants defined as a motor or sensory responses to a threshold stimulus of known size at known distance.
MEASUREMENT OF VISUAL ACUITY IN INFANTS A child should be aware & responsive to the surroundings & situation. A normal pupillary response, a positive blind response & an elicitable OKN indicate good visual acuity. VA improves rapidly during the 1st years of life than matures approximately 5-6 years of age
Fixation behaviour can be determined accurately in this age group as the fovea develops completely by 3 months of age. If the child habitually fixates with one eye, it indicates poor vision in the non fixating eye.
AGE GROUP  Infants (Birth – 14 months)  Toddlers (14 months – 2 1/2 years)  Pre-schoolers (2 1/2 years – 5 years)  School going children (5 years – 15 years)
NORMAL VISUAL DEVELOPMENT Very soon after birth – can fix & follow a light source. 1 months – fixation is central, steady & maintained. Can follow a slow target.  3 months – binocular vision & eye coordination. 6 months – reaches out accurately for toys. 9 months – looks for hidden toys. 2 years – picture matching 3 years – letter matching of single letters. 5 years – Snellen chart by matching or naming.
DIFFERENT TYPES OF VISUAL ACUITY TEST IN INFANTS  Opto kinetic nystagmus test  Preferential looking test  Visually evoked response  Catford drum test  Cardiff acuity card test  Indirect assessment of visual acuity  Hundred & thousand sweet test.  Lea paddle
OPTO KINETIC NYSTAGMUS TEST OKN drum has been proposed as a method of measuring visual acuity in children. In this test, nystagmus is elicited by passing a succession of black & white stripes through the patient’s field of vision.
Procedure: Striped patterns are presented on a rotating drum. The drum is moved in one direction in front of the patient. If the striped pattern is visible, the patients eyes will make ‘Rail road Nystagmus’ eye movements as they follow the movement of the stripes.
The clinician determine that elicits the nystagmus response when it is moving.
RECORDING New born 6/120 2 months 6/60 6 months 6/30 20-30 months 6/6
PREFERENTIAL LOOKING TEST PLT is used to assess VA in infants & young children who are unable to identify pictures or letters. Procedures: 1. The child is presented with two stimulus field. 2. One with stripes and the other with a homogenous gray area of the same average luminance as stripes randomly alternated.
3.Typically,infants and children will look at the more interesting stripes. 4.A small peephole is centered between the two fields, for observer. 5.Observer judges the location of the strips based on the child’s head & eye movements.
If the child can see the stripes, he/she will prefer to look them. If the child can’t see them, the child will not show a preference. Visual acuity determined with this method RECORDING New born 6/240 3 months 6/60 36 months 6/6
VISUALLY EVOKED RESPONSE It is quite useful in assessing visual function in infants. It is a electro encephalo graphic recording made from the occipital lobe in response to visual acuity. It is the only clinically objective technique available to assess the functional state of the visual system beyond the retinal ganglion cells.
Flash VER determines the integrity of macula & visual pathway function. Patter VER depend on form sense & gives rough estimate of the visual acuity.
CATFORD DRUM TEST It is a detection acuity test. It is useful in infants & preschool children. In this test, the children is made to observe an oscillating drum with black dots of varying sizes. The smallest dot that evokes pendular eye movements denotes the level of visual acuity
CARDIFF ACUITY TEST  The principle of the target design is that of the vanishing optotype.  The targets are pictures drawn with a white band border by 2 black bands, all on a neutral gray background.  The examiner simply observes the children’s fixation.
INDIRECT ASSESSMENT OF VISUAL ACUITY Blink reflex in response to sound. Menace reflex i.e; closure of the eyes on the approach of an object if vision is normal.
BINOCULAR FIXATION PREFERANCE Behaviour evidence of decreased vision in right eye. A small toy is used to get the child’s attention & the examiner covers the right eye to monitor fixation of the left eye. The child fixates on the toy without objecting.
When the left eye is covered , the child objects & tries to move the examiner’s hand. When the right eye is covered, the child does not object & tracks the object
CSM Method Done with one eye fixating on an accommodative target held at 40 cm. ‘C’ refers to the location of corneal light reflex fixates the examiner light at monocular conditions. Normally reflected light from cornea in near the centre of cornea and it should be positioned symmetrically in both eyes. If fixation target is viewed eccentrically, fixation is termed uncentral.
‘S’ refers to the steadiness of fixation at examiners light and also as it slowly moved about. ‘M’ refers to the ability of the patient to maintain alignment first with one eye then the other as the opposite eye is uncovered. Evaluation : CSM – 6/9 – 6/6 CSNM –6/36 – 6/60 Unsteady central fixation < 6/60
HUNDRED & THOUSAND SWEET TEST If child able to pick up small sweets at 33 cm, visual acuity is at least 6/24 or 20/80.
Lea paddle It is based on preferential looking and snellen principle . The chart is placed at a distance of 1m from the patient . It is usually used for the age group of 3 to 9 mths . There are cards available of various thickness of lines .
At a time two cards are held infront of the patient .The blank infront and the one with lines ie, held behind it . Then immediately the second card is flipped out and we keep on changing the positions. The patient should appreciate the card with lines . The test is done at same eye level and the eye movement of patient is seen .
Lea paddle
References… Theory and practice of optics and refraction—A.K Khurana Clinical visual optics. Internet.
THANK YOU……

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Visual acuity in infants

  • 2. VISUAL ACUITY  It is the resolving power of the eye. It is an ability to see two separate object as separate.
  • 3. VISUAL ACUITY IN INFANTS  Visual acuity, in preverbal infants defined as a motor or sensory responses to a threshold stimulus of known size at known distance.
  • 4. MEASUREMENT OF VISUAL ACUITY IN INFANTS A child should be aware & responsive to the surroundings & situation. A normal pupillary response, a positive blind response & an elicitable OKN indicate good visual acuity. VA improves rapidly during the 1st years of life than matures approximately 5-6 years of age
  • 5. Fixation behaviour can be determined accurately in this age group as the fovea develops completely by 3 months of age. If the child habitually fixates with one eye, it indicates poor vision in the non fixating eye.
  • 6. AGE GROUP  Infants (Birth – 14 months)  Toddlers (14 months – 2 1/2 years)  Pre-schoolers (2 1/2 years – 5 years)  School going children (5 years – 15 years)
  • 7. NORMAL VISUAL DEVELOPMENT Very soon after birth – can fix & follow a light source. 1 months – fixation is central, steady & maintained. Can follow a slow target.  3 months – binocular vision & eye coordination. 6 months – reaches out accurately for toys. 9 months – looks for hidden toys. 2 years – picture matching 3 years – letter matching of single letters. 5 years – Snellen chart by matching or naming.
  • 8. DIFFERENT TYPES OF VISUAL ACUITY TEST IN INFANTS  Opto kinetic nystagmus test  Preferential looking test  Visually evoked response  Catford drum test  Cardiff acuity card test  Indirect assessment of visual acuity  Hundred & thousand sweet test.  Lea paddle
  • 9. OPTO KINETIC NYSTAGMUS TEST OKN drum has been proposed as a method of measuring visual acuity in children. In this test, nystagmus is elicited by passing a succession of black & white stripes through the patient’s field of vision.
  • 10. Procedure: Striped patterns are presented on a rotating drum. The drum is moved in one direction in front of the patient. If the striped pattern is visible, the patients eyes will make ‘Rail road Nystagmus’ eye movements as they follow the movement of the stripes.
  • 11. The clinician determine that elicits the nystagmus response when it is moving.
  • 12. RECORDING New born 6/120 2 months 6/60 6 months 6/30 20-30 months 6/6
  • 13. PREFERENTIAL LOOKING TEST PLT is used to assess VA in infants & young children who are unable to identify pictures or letters. Procedures: 1. The child is presented with two stimulus field. 2. One with stripes and the other with a homogenous gray area of the same average luminance as stripes randomly alternated.
  • 14. 3.Typically,infants and children will look at the more interesting stripes. 4.A small peephole is centered between the two fields, for observer. 5.Observer judges the location of the strips based on the child’s head & eye movements.
  • 15. If the child can see the stripes, he/she will prefer to look them. If the child can’t see them, the child will not show a preference. Visual acuity determined with this method RECORDING New born 6/240 3 months 6/60 36 months 6/6
  • 16. VISUALLY EVOKED RESPONSE It is quite useful in assessing visual function in infants. It is a electro encephalo graphic recording made from the occipital lobe in response to visual acuity. It is the only clinically objective technique available to assess the functional state of the visual system beyond the retinal ganglion cells.
  • 17. Flash VER determines the integrity of macula & visual pathway function. Patter VER depend on form sense & gives rough estimate of the visual acuity.
  • 18. CATFORD DRUM TEST It is a detection acuity test. It is useful in infants & preschool children. In this test, the children is made to observe an oscillating drum with black dots of varying sizes. The smallest dot that evokes pendular eye movements denotes the level of visual acuity
  • 19. CARDIFF ACUITY TEST  The principle of the target design is that of the vanishing optotype.  The targets are pictures drawn with a white band border by 2 black bands, all on a neutral gray background.  The examiner simply observes the children’s fixation.
  • 20. INDIRECT ASSESSMENT OF VISUAL ACUITY Blink reflex in response to sound. Menace reflex i.e; closure of the eyes on the approach of an object if vision is normal.
  • 21. BINOCULAR FIXATION PREFERANCE Behaviour evidence of decreased vision in right eye. A small toy is used to get the child’s attention & the examiner covers the right eye to monitor fixation of the left eye. The child fixates on the toy without objecting.
  • 22. When the left eye is covered , the child objects & tries to move the examiner’s hand. When the right eye is covered, the child does not object & tracks the object
  • 23. CSM Method Done with one eye fixating on an accommodative target held at 40 cm. ‘C’ refers to the location of corneal light reflex fixates the examiner light at monocular conditions. Normally reflected light from cornea in near the centre of cornea and it should be positioned symmetrically in both eyes. If fixation target is viewed eccentrically, fixation is termed uncentral.
  • 24. ‘S’ refers to the steadiness of fixation at examiners light and also as it slowly moved about. ‘M’ refers to the ability of the patient to maintain alignment first with one eye then the other as the opposite eye is uncovered. Evaluation : CSM – 6/9 – 6/6 CSNM –6/36 – 6/60 Unsteady central fixation < 6/60
  • 25. HUNDRED & THOUSAND SWEET TEST If child able to pick up small sweets at 33 cm, visual acuity is at least 6/24 or 20/80.
  • 26. Lea paddle It is based on preferential looking and snellen principle . The chart is placed at a distance of 1m from the patient . It is usually used for the age group of 3 to 9 mths . There are cards available of various thickness of lines .
  • 27. At a time two cards are held infront of the patient .The blank infront and the one with lines ie, held behind it . Then immediately the second card is flipped out and we keep on changing the positions. The patient should appreciate the card with lines . The test is done at same eye level and the eye movement of patient is seen .
  • 29. References… Theory and practice of optics and refraction—A.K Khurana Clinical visual optics. Internet.