Farhana AdninB.Optom,4th batch

ICO.CU

Resolving power of the eye or the ability to see two separate objects as separate.

defined as the smallest target of known size at known testing distance correctly verbally identified by a child.

Visual disorders leading cause for childhood disabilities

Amblyopia;most common cause for monocular vision loss

Impact on reading skills & educational development

Early detection means PREVENTION & better TREATMENT

Infants (Birth – 14 months)

Toddlers (14 months – 21/2 years)

Preschoolers (21/2 years – 5 years)

School going children (5 years – 15 years)

Very soon after birth - Can fix and follow a light source, face or large, colorful toy.

1 months - Fixation is central, steady and maintained, can follow a slow target, and converge, preference of looking at face.

3 months - binocular vision and eye cordination, eyes follow a moving light or face, responsive smile.

6 months - Reaches out accurately for toys. 9 months – look for hidden toys. 2 years - Picture matching 3 years - Letter matching of single letters (e.g., Sheridan Gardiner) 5 years - Snellen chart by matching or naming

Use of the Landolt C format.

Use of single, isolated optotypes, rather than a full line or chart.

A two-alternative force choice or matching response.

Avoidance of the need for a verbal response or a directional response.

A short test distance such as 3 meters, rather than traditional 6 meters distance.

Marble game test

Sheridan’s ball test

Worth’s ivory ball test

Dot visual acuity test

Coin test

Miniature toy test

Illiterate E- cutout test

Tumbling E-test

Isolated hand figure test

Sheridan-Gardiner HOTV test

Kay picture test

Broken wheel test

Light home picture cards

It is used with children about 2 ½ -5 years of age

The child is given a cut out of an E & asked to match this E with isolated Es with varying sizes.

The first trial is not always successful.

The mother may be instructed to teach E-game at home

When the children starts understanding the orientation of E, a visual acuity chart consisting of Es oriented in various directions may be used.

When the children starts understanding the orientation of E, a visual acuity chart consisting of Es oriented in various directions may be used.

It consists of letter ‘E’ It has different sizes of E in one of the four

position( Right, left, upward & downward) The test is done at a distance of 6 meter. The child is given wooden or plastic letter E and is

asked to point the direction of E as instructed by the examiner .

Or the patient is directly told to point the finger in the direction up down ,left, right as shown in the main chart .

It is similar to E- cutout test.

Sjogren has replace the E with the isolated figure of a hand & in some children it works better than Es.

It is used for the age group of 2-5yrs .

It is done at 6 meter and if child can’t read 6/60 we can do it at 3 meter .

The chart is available in the form of spiral booklet .

The main chart consists of letters HOTV of different size .

These letters are arranged may be in circular form to give proper orientation so that child can identify them properly .

The child is given a key card and is asked to match with the letter as shown in the main card.

The four letter ‘HOTV’ are only used as they are considered as standard letters for measuring visual acuity .

More over it is found that these letters are more child friendly .

It is done at a distance of 10 to 20 foot distance .

The main chart consist of pictures of eating items or toys .

The child is given a key card and is asked to match with the pictures as shown in the main chart by the examiner .

It is done at a distance of 3meter.

The chart is available in simple as well as spiral booklet form .

The main card consist of 5 symbols with one symbols in centre and the rest 4 are located in circular form around the central symbol .

These arrangement is done in particular to develop both crowding and confusing phenomenon for the child difficulty .

The examiner shows normally centre symbol but at the same time he can ask for other symbols too.

The patient is given a key card to point out the symbol .

These symbols are fixed and are kept a standard like apple ,house ,circle ,square etc ..

The size of pictures goes on decreasing from 3/9.5 to 3/2.4 and there are four cards for each size .

The size of pictures goes on decreasing from 3/9.5 to 3/2.4 and there are four cards for each size .

It is used for children of 2-3 yrs .

The test is done at distance of 6 meter .

It is based on snellen principle .

The chart is in the form of spiral booklets .

Each page has a single picture .

The size goes on decreasing from 6/60 to 6/6 with each size having 3 cards.

Again the patient is given a key card and is asked to match with the picture as shown in the main chart .

It is usually used for age group of 3 to 6 yrs who cannot recognize letters .

The chart consist of broken circles with each broken ring subtending an angle of 5 min at nodal point .

The chart is shown to the patient at a distance of 6meter .

The patient has to identify the part from where the ring is broken by pointing the direction up ,down ,left,right by finger .

Landolt ‘c’-chart based on log MAR principle are also available .

They consist of 5 rings per line and the size goes on decreasing as we move a head .

Consist of 8 pair of test cards

20/20, 20/25, 20/30, 20/40, 20/60, 20/80, 20/100, 20/120.

Each card has a black line drawing of a car on a white background.

1 with solid wheels,other with broken wheels.

Done from 3m distance

2 cards are held before the child

He simply identify which one is broken wheel

If the child can distinguish which car has the broken wheels,itindicates that he can resolve the gap size of the landolt C for the particular card

If acuity is less than 20/120,steps are repeated at 1.5m distance

Visual acuity is recorded as the last set of cards at which the child correctly respond.

A chart containing an apple, a house and an umbrella, arranged in

Snellen’s equivalents of 20/200-20/10 is used, and

The child is asked to identify the pictures along the lines.

The test is carried out at 10 ft 12 cards are available, size of each card is

4×5 inch

•Here 6 pictures have been used --Horse, Bird, Cake, Hand Car and Telephone •Card size : 4 × 4 inch with white background •distance of 3 meter .

The child is first shown cards at close range with both eyes open and is asked to name each picture .

Then one eye of patient is occluded

Then the child is asked to call off the names of the pictures he sees

Similar process is done with other eye & both eye open

OD,OS,OU recorded

If he incorrectly read 20/40line,acuity as

20/40-1or 20/30+3

Black dots on white background

Touch a black dot

Test dist--25 cm

VA--20/800 to 20/20

PROCEDURE…….

Child is shown an illuminated box with black dots of different sizes printed on it

The smallest dot identified denotes the visual acuity of the child

The child is asked to identify the 2 faces of coins of different sizes held at different distances.

Procedure:

In this test the child are shown a miniature toy from a distance of 10ft .

Asked to name or pick the pair from the assortment.

In children of 1-2 years of age reaching or placing games can be used to estimate visual function.

The game is the marble game.

This test is not intended to measure visual acuity of each eye.

The child is asked to place marbles in the holes of a card or in a box.

Compare the functioning of the childs eye when one or the other is closed.

The vision of an eye is then noted as being useful or less useful.

Mary Sheridan used a series of Styrofoam balls of progressively smaller size.

Procedure

One record the smallest ball that the infant can fixate and follow at a distance of 10ft.

Rolling the ball on a white or grey background and asking the child to pick it up.

Procedure

Ivory balls 0.5 to 2.5” in diameter are rolled on the floor in front of the child and he is asked to retrieve each.

Visual acuity is estimated on the basis of smallest size for the

test distance.

THEORY AND PRACTICE OF OPTICS & REFRACTION…A.K.KHURANA

CLINICAL PROCEDURE OF OPTOMETRY

CLINICAL VISUAL OPTICS ..REBETT & BENNET

INTERNET