visual acuity estimation in children in Optometry
- 1. PEDIATRICVISUAL ACUITY ESTIMATION Name : Halima Khatun Student Code : BWU/BSO/21/014 Course Name : Clinical Examination of Visual System Course Code : BOPTOC405 Programme Name : Bachelor of Optometry Department : Allied Health Sciences
- 2. Content ◦ Visual acuity ◦ Measurement of visual acuity in infants ◦ Assessment of visual acuity from 1-3 years ◦ Measurement of visual acuity in preschool children (3-5years) ◦ Measurement of visual acuity in school children (above 5 years)
- 3. Visual Acuity ◦ Visual acuity consists if the following : ◦ Minimum visible : detection of presence or absence of stimulus ◦ Recognition : to identify the object ◦ Minimum discriminable : the minimum separation required between two dark bars to discriminate ◦ Resolution : measurement of the threshold of discrimination . The normal angular threshold of discrimination for resolution measures approx. 30-60s of an arc which is known as MAR.
- 4. Measurement of visual acuity in infants ◦ From birth up to 3 months : 1. Blink reflex test – Present since birth .When bright light is shown ,a normal infant should respond by blinking. 2. Pupillary light reflex test : presence of this reflex determines that patient is having vision. 3. Vestibulo- ocular reflex : tested by turning the newborn’s head on his/her axis and observing doll’s eyes response . 4. OKN test : here nystagmus is elicited by passing a succession of black and white strips by means of OKN drum (size 10*8 inches),rotated at 8-10 rpm through the patient’s field of vision.
- 6. Assessment of visual acuity in infants ◦ From 3 to 6 months : 1. CSM method : asked to fixate on pen light ; A small target is coupled with light held in front of the child and moved slowly . Nystagmus results in unsteady fixation . Check the ability to keep the eye fixed when other eye is covered. 2. Bruckner red reflex test : evaluate strabismus
- 7. Assessment of visual acuity in infants ◦ 6 to 12 months Catford drum test : child is made to observe an oscillating drum with black dots varying sizes ranges from 0.5 to 15mm in diameter representing vision between 6/6 and 2/60. Rotation of disc at a distance of 60 cm evokes pendular movements. The smallest dot that evokes pendular eye movements denotes the level of visual acuity.
- 8. Assessment of visual acuity from 1 to 3 years 1. Cardiff acuity card tests : vanishing optotype .Target – line drawings of pictures of fish, car etc. The black and white lines forming the pictures become finer with each set of 3 cards until picture the picture is lost. A total 11 set of cards are available from 20/400 to 20/20 . 2. Coin test : Coins of different sizes are shown to child and child is asked to identify the two faces of coins held in different distances . 3. Miniature toy test : in this test, the child is shown a miniature toy from a distance of 10ft and is asked to name or pick the pair from the assortment.
- 10. Measurement of visual acuity in preschool children ◦ 3 to 5 years : ◦ Landolt‘s C test : use to test minimum separable acuity. Landolt‘s Cs are presented with the opening of the optotype at 3,6,9,12 o’clock clock. The child has to tell where the opening is. The separation at the break in the C represents 1min of arc and the entire C subtends 5min of arc at the eye for 20/20 . ◦ Lea symbols test : optotypes are read at a distance of 10- 20ft.This is a good way to test individuals who do not use the Western alphabet. Hence, it eliminates the problem with language barriers.
- 11. Measurement of visual acuity in school children ◦ 5 years and above 1. Snellen’s visual acuity chart : The visual acuity test is used to determine the smallest letters you can read on a Snellen chart held 6 meters away. 2. LogMAR chart : comprises rows of letters and has equal number of letters in each line. It is used at a distance of 4m. It is designed to enable a more accurate estimate of acuity as compared to other charts.
- 12. Thank you