Pediatric Optometry

Pediatric Optometry Pediatric Optometry

Lecture 2 Lecture 2

Child visual developmentChild visual development

Mutez Gharaibeh,MDMutez Gharaibeh,MD

Monocular devlopment .Monocular devlopment . Binocular development ----- Amblyopia .Binocular development ----- Amblyopia .

Most of eye growth occurs in first 2 -3 yrs Most of eye growth occurs in first 2 -3 yrs of life .of life .

Congenital glaucoma --- Buphthalmos Congenital glaucoma --- Buphthalmos Adult glaucoma ---- No buphthalmos Adult glaucoma ---- No buphthalmos

Corneal size ↑ by ≈ 50%Corneal size ↑ by ≈ 50% Retinal surface area 590 mm2----- 1250 Retinal surface area 590 mm2----- 1250

mm2mm2 Axial length 16.8mm-----23.6mm ( +7)Axial length 16.8mm-----23.6mm ( +7) Corneal power 51.2 D ----43.5DCorneal power 51.2 D ----43.5D Lens power 34.4 D ---- 18.8DLens power 34.4 D ---- 18.8D

( - 30D)( - 30D)

Refractive errorsRefractive errors

The average refractive error in children from birth to 1 year of age is about 2 diopters (D) of hyperopia .

Astigmatism up to 2 D is common in children under 3 years of age.

Low amounts of anisometropia are common and variable in infants.

Studies show that 30-50 percent of infants less than 12 months of age have significant astigmatism, which declines over the first few years of life, becoming stable by approximately 2½ to 5 years of age.

< 3.5 yr --- usually against the rule . >3.5 yr --- usually with the rule .

With the rule With the rule against against oblique oblique

G9mIHRoG9mIHRoG9mIHRo

RetinaRetina

Foveal region gets to be thinner ( 1000Foveal region gets to be thinner ( 1000ллm m --- 700 --- 700 ллm ) by 4 yrs.m ) by 4 yrs.

Cones density/area increases by age.Cones density/area increases by age. More peripheral retina develops More peripheral retina develops

faster than foveal area.faster than foveal area. X,Y,W ganglion cells.X,Y,W ganglion cells.

propertiespropertiesX- typeX- typeY- typeY- typeW-typeW-type

SizeSizeMediumMediumLargeLargeVariableVariable

Dendritic Dendritic spreadspread

SmallSmallMediumMediumLargeLarge

ResponseResponseSustained briskSustained briskTransient briskTransient briskSustained Sustained sluggishsluggish

ConductionConductionMediumMediumFastFastSlowSlow

Receptive Receptive field sizefield size

SmallSmallMediumMediumLargeLarge

ProjectionProjectionLGN ( Parvo)LGN ( Parvo)LGN( Magno)LGN( Magno)LGNLGN

Static targets Static targets ( low frequency ( low frequency flickers)flickers)

Moving targets Moving targets ( high grefuency ( high grefuency flicker)flicker)

LGNLGN

LGNLGN

The main difference between infants and The main difference between infants and adults is the size .adults is the size .

Parvocellular layers reach adult size by Parvocellular layers reach adult size by end of 12 months. end of 12 months.

Magnocellular layers reach adult size by Magnocellular layers reach adult size by end of 24 months.end of 24 months.

Visual acuityVisual acuity

the spatial resolving capacity of the visual the spatial resolving capacity of the visual system .system .

Spatial resolutionSpatial resolution= = angular resolutionangular resolution =describes the resolving power of the eye.=describes the resolving power of the eye.

Resolving powerResolving power is the ability of the is the ability of the components of an imaging device( e.g: components of an imaging device( e.g: eye) to measure the eye) to measure the angular separation of of the points in an object .the points in an object .


Visual acuity is limited by diffraction, Visual acuity is limited by diffraction, aberrations and photoreceptor density in aberrations and photoreceptor density in the eye .the eye .

a number of factors also affect visual a number of factors also affect visual acuity such as refractive error, illumination, acuity such as refractive error, illumination, contrast and the location of the retina contrast and the location of the retina being stimulatedbeing stimulated. .


Target Target detection detection requires only the perception of requires only the perception of the presence or absence of an aspect of the the presence or absence of an aspect of the stimuli .stimuli .

Landolt C and the Illiterate E are forms of Landolt C and the Illiterate E are forms of detection used in visual acuity measurement in detection used in visual acuity measurement in the clinic.the clinic.


Target Target recognition recognition tasks tasks

6/66/6) ) 20/2020/20((

logMARlogMAR

Vernier acuityVernier acuity

Vernier acuity is the ability by a person to Vernier acuity is the ability by a person to detect the proper alignment of two line detect the proper alignment of two line segments segments

Grating acuityGrating acuity

aspect of visual acuity involving the ability aspect of visual acuity involving the ability to distinguish the elements of a fine to distinguish the elements of a fine grating composed of alternating dark and grating composed of alternating dark and light stripes or squares . light stripes or squares .

Angular acuityAngular acuity = Reading a letter = Reading a letter Morphoscopic acuityMorphoscopic acuity =Reading a letter in a =Reading a letter in a

line.line. Crowding phenomenaCrowding phenomena==

Development of visual acuityDevelopment of visual acuity Visual acuity contrast sensitivityVisual acuity contrast sensitivity

Birth ≈ 6/300 unknownBirth ≈ 6/300 unknown 3 months 6/90 --- 6/60 ≈ 6/603 months 6/90 --- 6/60 ≈ 6/60 1 yr ≈ 6/24 ≈ 6/9 1 yr ≈ 6/24 ≈ 6/9 2 yrs ≈ 6/12 --- 6/9 ≈ 6/6 2 yrs ≈ 6/12 --- 6/9 ≈ 6/6 3 yrs ≈6/9 ---6/6 ≈ 6/63 yrs ≈6/9 ---6/6 ≈ 6/6

Saccadic system Saccadic system Smooth pursuit systemSmooth pursuit system Optokinetic nystagmus Optokinetic nystagmus

Babies are not born with all the visual Babies are not born with all the visual abilities they need in life .abilities they need in life .

The ability to focus their eyes, move them The ability to focus their eyes, move them accurately, and use them together as a accurately, and use them together as a team must be learned .team must be learned .

Eye and vision problems in infants can Eye and vision problems in infants can cause developmental delayscause developmental delays..

Visual milestonesVisual milestones

Not every child is the same and some may Not every child is the same and some may reach certain milestones at different agesreach certain milestones at different ages..

Birth-4 moBirth-4 mo Up to about 3 months of age, babies' eyes do not focus Up to about 3 months of age, babies' eyes do not focus

on objects more than 2-3 meters from their faceson objects more than 2-3 meters from their faces..

By eight weeks, babies begin to focus their eyes on the By eight weeks, babies begin to focus their eyes on the faces of a parent or other person near themfaces of a parent or other person near them.. But they still But they still cannot follow.cannot follow.

For the first two months of life, an infant's eyes are not For the first two months of life, an infant's eyes are not well coordinated , However, if an eye appears to turn in well coordinated , However, if an eye appears to turn in or out constantly, an evaluation is warrantedor out constantly, an evaluation is warranted..

Babies should begin to follow moving objects with their Babies should begin to follow moving objects with their eyes and reach for things at around four months of ageeyes and reach for things at around four months of age..

5-85-8 monthsmonths During these months, control of eye movements and During these months, control of eye movements and

eyeeye--body coordination skills continue to improvebody coordination skills continue to improve.. Depth perception is not present at birthDepth perception is not present at birth. . It is not until It is not until

around the fifth month that the eyes are capable of around the fifth month that the eyes are capable of working together to form a threeworking together to form a three--dimensional view of the dimensional view of the world and begin to see in depthworld and begin to see in depth..

it is generally believed that babies have good color vision it is generally believed that babies have good color vision by five months of ageby five months of age..

Most babies start crawling at about 8 months old, which Most babies start crawling at about 8 months old, which helps further develop eyehelps further develop eye--handhand--footfoot--body coordinationbody coordination. . Early walkers who did minimal crawling may not learn to Early walkers who did minimal crawling may not learn to use their eyes together as well as babies who crawl a lotuse their eyes together as well as babies who crawl a lot..

9-129-12 monthsmonths At around 9 months of age, babies begin to pull At around 9 months of age, babies begin to pull

themselves up to a standing positionthemselves up to a standing position. . By 10 months of By 10 months of age, a baby should be able to grasp objects with thumb age, a baby should be able to grasp objects with thumb and forefingerand forefinger..

By twelve months of age, most babies will be crawling By twelve months of age, most babies will be crawling and trying to walk. Parents should encourage crawling and trying to walk. Parents should encourage crawling rather than early walking to help the child develop better rather than early walking to help the child develop better eye-hand coordination.eye-hand coordination.

Babies can now judge distances fairly well and throw Babies can now judge distances fairly well and throw things with precision. things with precision.

12-2412-24 monthsmonths

By two years of age, a child's eyeBy two years of age, a child's eye--hand hand coordination and depth perception should coordination and depth perception should be well developedbe well developed..

Children this age are highly interested in Children this age are highly interested in exploring their environment and in looking exploring their environment and in looking and listening. They recognize familiar and listening. They recognize familiar objects and pictures in books and can objects and pictures in books and can scribble with pencil.scribble with pencil.

What do you need to know about What do you need to know about child visual developmentchild visual development

1- Summary + table 3.4 ( page 70).1- Summary + table 3.4 ( page 70). 2- slides.2- slides.

Thank You Thank You

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Pediatric Optometry