Real Refractive error and spectacle correction.ppt

Bipin Koirala
Master’s of Optometry
Himalayan Eye Institute

 To determine the refractive status in infants and preverbal
children’s
 Must be appropriate for non-verbal ,uncooperative, non-
communicative children’s
 Must provide important information in refractive state of
eye
 Must be understandable ,easily assessable and accessible
 Practitioner must be competent enough to deliver a
perfect judgement

 As a child have a great ability to maintain a wide range of
accommodation
 Un-cooperative
 Greater range of accommodation
 Difficulty in quantifying visual status
 Risk of visual deprivation
 Difficulty in making a child understand wear glasses
So, cycloplegic refraction must be
carried out in every patient with or
without strabismus

 Premature infants :- Mostly presented with high myopia
a/w ROP
 Full term newborn :- Mostly presented with hyperopia of
(+1-2 D)but refractive error might range b/w from +11 to -
11 D
 Preschool child :- Shift towards emmetropia / small
myopia / less hyperopia
 School children :- Emmetropia / school myopia
 Adolescent :- Mostly myopia

Pediatric
Refraction
Objective
Refraction
Keratometry
Ophthalmoscopy
Auto refractor
Retinoscopy
Static
Retinoscopy
Dynamic
Retinoscopy
Near
Retinoscopy
Photorefraction
Subjective
Refraction

Indications
of cyclo
refraction
Pseudo
myopia
Poor
endpoint
of
refraction
Strabismus
Latent
hyperopia
Young
children

 Every nonverbal and Non Communicative children
 Patient with High Heterophoria
 Accommodative Esotropia ( Atropine is best choice)
 Accommodative Asthenopia
 Poor reliability b/w dry retinoscopy objective finding
with subjective finding.

 After detection & measurement of refractive error its
proper management is next most important part in
pediatric refraction.
 Clinician must be aware about normal and abnormal
refractive findings & also the normal development of
various optical components

 Along with Refraction & prescription other
optometric test procedures must go hand in hand
 Eg. Orthoptic examination, Fundus evaluations , so
that proper management of an condition can be
done.

 A number of researches had been carried out regarding
power prescription in pediatric age groups.
 AAO , AOA and other well renowned associations have
given their own opinion regarding power prescription.
 Beside this clinical experience of a clinician & his
personal decision also plays major role in power
prescription.

 Is the refractive error in normal range with child’s age?
 Will this refractive error of the child emmetropize?
 Will this level of refractive error disturb normal level of
functional vision?
 Will prescribing glass be beneficial for the child?
 Will prescribing glass interfere with emmetropization?

Classification of Hyperopia
Classification is on the basis of Refractive error amount.
Type Amount
Low Hyperopia < or = 2.00 D
Moderate Hyperopia + 2.25 to + 5.00 D
High hyperopia > 5.00 D

Symptoms depends on age of child and also the degree
of error
1. Squinting and rubbing of eyes
2. Frequent blinking
3. Avoidance of near work
4. Asthenopia
5. Poor school performance
6. Deviation of eyes (eso)
7. Blurring of vision

 High amount of error.
 Pts / child complains reduced VA.
 Error A/w Amblyopia & Deviation.
 A/w syndromes having probability of amblyopia
 History of poor school performance

 Before prescription proper VA must be determined and
any deviation in eyes must be ruled out.
 If deviation is absent cycloplegic refraction with
cyclopentolate (1%) can be considered.
 If deviation is present full cycloplegia is mandatory with
Atropine

Guidelines for prescription
in Hyperopia in
flowchart:-

Isometropic
Hyperopia
Deviation
+ce (eso)
Deviation
-ce
Full cycloplegic
correction given when
error is (> or = 2 D) and
regular F/U for error
below this
Prescribe only when
error is (> or = 5 D )
i.e. partial or 2/3rd
prescription is advised

Hyperopic
Anisometropia
< 2.50
D
> Or =
2.50 D
No prescription
needed ( follow up
3-6 monthly)
Partial
Prescription
(no devation )
Full prescription
(esodeviation +ce )

Isometropic
Hyperopia
Deviation
+ce (eso)
Deviation
-ce
Full cycloplegic
error is (> or = 2 D) and
below this
Prescribe only when
error is (> or = 3.5 D )

Hyperopic
Anisometropia
< 2.00
D
> Or =
2.00 D
No prescription
needed ( follow up
3-6 monthly)
Partial
Prescription
(no devation )
Full prescription
(esodeviation +ce )
Note:- If Exo deviation is associated plus
correction must be reduced

Isometropic
Hyperopia
Deviation
+ce (eso)
Deviation
-ce
Full cycloplegic
error is (> or = 1.5 D) and
below this
Prescribe only when
error is (> or = 2.5 D )

Hyperopic
Anisometropia
<1.50
D
> Or =
1.50 D
No prescription
needed ( follow up
3-6 monthly)
Partial
Prescription
(no devation )
Full prescription
(esodeviation +ce )
Note:- If Exo deviation is associated plus
correction must be reduced

 Cycloplegic refraction is always recommended when
hyperopia is present in initial retinoscopy.
 Since school children need good vision for both distance and
near proper correction is always needed for better academic
performance.
 At school age a child is expected to be nearly emmetropic.
 Prevention of a child from amblyopia is major concern if high
hyperopia , deviation & anisometropia is present.

 Isometropic error (> or = 1.50 D) in the school years
(without symptoms) is indicated for correction.
 A full or near full correction may be given at this age,
as emmetropization has essentially ended.
 Hyperopic Anisometropia (> or = 1.00 D ) needs full
correction.

Guidelines for Prescription
in Myopia

 It is based on degree of refractive error
Type Amount of Error
Low Myopia < or = 2 .00 D
Moderate Myopia 2.00-6.00 D
High Myopia > 6.00 D

Signs
1. Predominant eyeball
( large & prominent)
2. AC is slightly deep
3. Pupils are somewhat
larger.
4. Temporal myopic
crescent in fundus
Symptoms
1. Poor distance vision
2. Squinting eyes
3. Asthenopia
4. Change in psychological
outlook like as introvert ,
only interested in indoor
games close holding of
books
5. Poor performance in
class

 Infants with low-to-moderate myopia may not need
prescription.
 Because they don’t need to view things in fine details.
 But AAO gives prescription guidelines in such
condition as :-
Isometropic
Myopia
< -
5.00D
> or =
-5.00D
No need to prescribe
(constant monitoring)
Needs prescription
(Reduce by 1-2 D)

 AAO suggests prescription of glasses when Myopic
anisometropia is ( > or = 2.50 D) in infants to reduce
possible chance of amblyopia.
 High amount of myopia at birth is likely to produce
esotropia becoz far point is very close to eye .

 No prescription is given for low myopia in toddlers but given for
moderate and high myopia.
 Prescription indicated as per guidelines of AAO.
Isometropic
Myopia
< -
4.00D
> or = -
4.00 D
Needs prescription
(Reduce by 1-2 D)
(for no deviation)
Example : Highly myopic children appear to do well without correction and
cannot always tolerate their full prescription. A two-year-old myope needing -
15.00DS may cope better with -10.00DS for a few months before gradually
increasing the prescription.

 AAO suggests Anisometropic myopia > or = 2.50 D needs
prescription in toddlers to prevent probable chance of amblyopia
& deviation .
For Muscle Imbalances:
For Eso deviation : minimum minus for clear vision
For Exo deviation : maximum minus for clear vision

Isometropic
Myopia
< -
3.00
D
> or =
-3.00
D
Needs prescription
(Reduce by 1-2 D)
(for no deviation)

 AAO suggests Anisometropic myopia > or = 2.00 D needs
prescription in preschoolers to prevent probable chance of
amblyopia & deviation .
 Similarly if amblyopia is associated with myopia but no
strabismus 2/3rd of cycloplegic correction can be given for
children’s below 6yrs .
For muscle imbalances
For eso deviation : Minimum minus for clear vision
For exo deviation : Maximum minus for clear vision

 Need proper vision for both near & distance at school
age so proper Rx for both near & distance is needed.
 Although Emmetropization almost completed at 6 yrs.
of age but still risk of deviation & Amblyopia is present

 Full prescription must be given to abolish Amblyopia ,
deviation & avoid symptoms like squinting eyes.
 Over correction must be avoided becoz overcorrecting
myopia can be detrimental and may cause
accommodative spasm leading to severe asthenopia and
esotropia
 Only one circumstance where over minus glasses may be
prescribed is the presence of intermittent divergent
strabismus.

 Minus glasses are used to induce accommodation and
thus accommodative convergence to control
exotropia.
 Slight under correction is done if a/w esophoria child
more than 6 yrs.
 In very high myopia (> or = 10.00 D ) full correction
can be barely tolerated so under correction is
recommended.

 Similarly in Anisometropic Myopia ( > or = -2.00 D ) must
be prescribed to prevent amblyopia.
For muscle imbalances
For Eso deviation : Minimum minus for clear vision
For Exo deviation : Maximum minus for clear vision

Guidelines for Spectacle
prescription in
Astigmatism

 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
 Large cylinders in infancy will usually emmetropise, so
do not prescribe immediately and not before one year.

 About 2.00 D astigmatism is normal in infants and
1.25 D astigmatism in toddlers and preschoolers
 Main risk & challenge with astigmatism is prevention
of meridional amblyopia.
 The visual system may not be very sensitive to
uncorrected astigmatism in the first year of life.

From 1 year onwards, there is evidence that uncorrected
astigmatism, particularly oblique astigmatism, is associated
with meridional amblyopia.
But in contrast Dobson and colleagues found no evidence
of meridional amblyopia in six‐month‐olds up to
three‐year‐olds with astigmatism of 2.00 D or more.

 In three‐ to four‐year‐olds, 1.50 D or more of
astigmatism is associated with poorer recognition
acuity, such that for every dioptre increase in cylinder,
there was a half‐line decrease in VA.
 Astigmatic anisometropia (either myopic or hyperopic)
had to be greater than 1.50 D before amblyopia
occurred.

1. Blurring of vision (even with low astigmatism)
2. Habit of rubbing & squinting
3. Pts complains circle being oval shaped &
point light appears tailed off
4. Asthenopia ,tiredness , fatigue
5. Tilting of head
6. Burning & itching sensation
In regard of symptoms and severity astigmatic patients
are more symptomatic..

Which type of astigmatism among two is more
symptomatic?

 Flowchart is according to AAO guidelines
Isometropic
Astigmatism
< 3D
> or
= 3D
Needs prescription i.e 3/4th
can be given (*we usually
prefer to monitor in
consecutive follow up)
Anisometropic
Astigmatism
<
2.5D
>
or=
2.5D
Needs prescription ( AAO).
Prescribing only after
monitoring and without
hampering emmetropization

Isometropic
Astigmatism
<
2.5D
> or
=
2.5D
Needs prescription i.e
3/4th can be given.
Anisometropic
Astigmatism
< 2D
> or
= 2D
Needs prescription ( AAO).
Prescribing full if amblyopia is
+ce
Partial (3/4th) if amblyopia is -
ce

Flowchart is according to AAO guidelines
Isometropic
Astigmatism
<
1.5D
> or
=1.5
D
Needs full
prescription(reduced
prescription can be given to
adapt initially)
Anisometropic
Astigmatism
(*above 4yrs)
<1.5
D
>
or=
1.5D
(constant monitoring &
F/U)
Needs full prescription ( AAO)
if amblyopia (+ce) & if no
amblyopia is seen initial partial
can be given later shifting to
full Rx
Pre Schoolers(3-6)yrs.

Isometropic
Astigmatism
<
0.75D
> or
=0.75
D
Needs full prescription(
prescription also depends on
symptoms)
Anisometropic
Astigmatism
<
0.75D
> or
=0.75
D
(constant monitoring & F/U),
(*prescription if symptomatic)
Needs full prescription ( AAO)
if amblyopia (+ce) & if no
amblyopia is seen initial partial
can be given later shifting to
full Rx
Schoolers(above 6)yrs.

 If Hyperopia is associated with Exophoria/ Tropia with
astigmatism then minimum minus cylinder can be
prescribed after transpose.
 If myopia is associated with esodeviation and
astigmatism plus cylinder can be prescribed.

Real Refractive error and spectacle correction.ppt

 High induced Hyperopia
 Against rule astigmatism
 Absence of accommodation
So all above problems must be
properly addressed during power
prescription

 In first few months Overcorrect by (2.00 to 3.00 D),
because the child’s world is near.
 Later at about 1 yrs of life overcorrection us reduced
to (+1 to + 1.50 D) to single vision intermediate add.
 After 1yrs of age or on reaching pre school period
bifocal prescription can be considered.

 Laurence gave a formula to predict spectacle
power in aphakic children's.
 Example:- A child is (B/L) hyperopic by +2 D before
surgery and power that must be given to him after
surgery is + 12 D..
F aphakic = +11.00D + ½ ( F preoperative)

 Repeated refraction and follow up in 3-6 months
 Aspheric lenses , lenticular design as glass option .
 High index glasses can be given
Unilateral aphakia is better
corrected with contact
lenses than spectacles
Pseudophakics should be
corrected fully for distance
as well as near with bifocals
or progressive lenses

Accommodative
Esotropia
Congenital
Aphakia
Down’s
syndrome
Pseudophakic
Constant
Esotropia
Or IET
Esophoria

Albinism
Astigmatism in
all subtypes a/w
myopia or
hyperopia
ROP High myopia

 Hyperopia a/w
WTR astigmatism
Down’s
syndrome
Nanopthalmos
High hyperopia
upto + 20 D

Sclerocornea &
Cornea plana
High
Hyperopia
Congenital defects
like marfan’s
syndrome ,
homocystinuria
Myopic Error
( most
commonly)

• Dispensing of children age ranging below 16
years(Babies to mid-teens)
• It is not only for the correction of refractive error
• Also to correct binocular vision anomalies such as
strabismus, Amblyopia, or convergence anomalies
• Challenging task

 More difficuly
 Duality of client
 Time taking task
 Measurement errors are unacceptable

 Must fit correctly (anatomically)
 Should be comfortable and durable
 Must not hamper the natural development of the nose
 Must be aesthetically acceptable
 The practitioner needs to ensure that the pupils and lenses
are correctly centered
 Safety is of primary concern

Characteristics of good kids’ frames
lower crest
larger frontal angle

 larger Splay
 Flatter Pantoscopic tilt

• Smaller frontal width
• Shorter length to bend
• Shorter length of drop
• Smaller boxed lens size
• Shorter back vertex distance

 Spring hinges to allow for children taking their
spectacle off with one hand and general hard wear.
 Over 95% of frames dispensed to children are metal.
It should be ensured that the frames have no sharp
edges.

 Titanium is an ideal material for children as it is
strong, durable and holds its adjustment well.
 Cellulose acetate, polyamide, optyl are plastic
materials

 Deep lens grooves for more securely seated lenses
 Silicone-based rubber frames for babies and children
who require indestructible frames-light and pliable
 No metal hinges reducing chances of facial injury in
small children's

Faces and Frame selection in children
 Square faces: Soft curves
 Round faces: Angular shapes
 Short face: Shallow frame
 Color matching: Consider skin color

 Frame front/width
 Eye size
 Nasal Bridge
 Temple and joints

 Frame height
 Pantoscopic tilt
 Vertex distance
 Face form angle

 Frame front should not be too wide that may cause
frequent falling or loosening.
 Too small frame may make child reluctant to wear the
frame and also may mark the soft and delicate skin
around the temporal regions.

Attractive color and beautiful designs may increase
compliance among children to wear glasses.

 Eye size should be bit smaller.
 High power lenses tend to get heavy, unattractive
and changing pantoscopic angle, vertex distance etc.
would be difficult with large eye size.

 Narrow bridge should be used to avoid frame from
slipping down.
 Bridge should fit properly such that entire weight of
the spectacle is not carried by crest.
 Nose bridge for children should have contact
surface as large as possible.

 The bridge selected should not allow the eyewires
to ride on the cheeks because it not only painful can
also cause permanent ridge to be formed

 Weight of spectacle can be evenly distributed over
large area using larger nose pads
 Saddle, keyhole bridge with accurate fit
 Strap bridge

Fitting children needs to be
A larger pad splay angle (more flare to the pad).
A larger pad or contact surface area helps the
frame sit better

 It is better to use appropriate temple length.
 Use skull type of temple or riding bow type.
 The curl of the sides must stop just short of the ear
lobe and sit along back of the ear.
 Curl of sides should be covered in silicone for comfort
and durability.

 Temple joint with frame front should be at the
middle to avoid frame falling down and child viewing
from over frame.
 Temple joint should be flexible or have spring on it or
180 degree.
 Temple shouldn’t touch the side of the head until
reaching the ear-point.

 Frame Height
Children have higher cheek position so ensure
appropriate lens height.

 Face form angle
 Face form lens are good for children as it not only
protects eyes but also vertex distance can decreased.
 Face form lens has good grip on child's face.
 Vertex distance
Fit with as close vertex distance as possible to reduce
aberration and ensure clear vision.

The ideal lens should be
 Impact resistant and durable (children are heavy handed)
 Light and comfortable
 Relatively thin
 Ideally should give full UV protection

Materials Consideration??
• Hard coated CR39, Polycarbonates, Trivex and High
index plastics
• Glass lenses are too dangerous and inappropriate for
this group.

 IPD measurement
 Vertex distance
 Lens type

 Proper measurement to ensure optical clarity and
reduce unwanted prismatic effect.
 For older children can use a pupillometer
 For younger children use a PD rule
 For very young children or for strabismic cases
(uncooperative to fixate his eye ) can use a PD rule
measuring limbus to limbus and inner canthus to
outer canthus distance can also be measured.

Vertex distance
Vertex distance should be as close as possible:
 For good Optical clarity by reducing peripheral
aberration
 For maximizing visual field by removing ring
scotoma by thick frame of child.

Optical Centers should be as close as possible to
the geometric centers, using the principal
axis/center of rotation rule
Drooping the optical center 1 mm below the pupil
center for every 2 degrees of pantoscopic tilt

 Children usually tend to break their frames and in
few cases lens also.
 Either hard coated polycarbonate or Trivex ( 10x
impact resistance than CR-39) lens can be
prescribed.

• Children lenses scratch more easily
• Hard coat to prevent from easy scratch
• For good optical quality, anti reflection coating is
must. Hence multi coated lenses is desired
• Children should be taught about proper frame
handling, placement and lens cleaning procedures.

 Weight of a lens depends on prescription and
specific gravity of the material used
 Heavy thick lens in high power not only affect optical
clarity but also affects frame stability during wear.
 Lenticular lenses given in high plus lenses.
 High index thin lens are desirable as little thinner
lens can be used

Lens material CR 39 Polycarbonate Trivex High index plastics
Impact
Resistance
Good Impact
Resistance
High Impact
Resistance
High Impact
Resistance
Very strong and
shatter Resistance
Surface
Durability
Inherent scratch
resistance
Very soft Good resistance
to scratching
and cracking
Thinner lenses
Coated with anti-
scratch hard coats
UV Protection Up to 355 nm Up to 285 nm Up to 380 nm 380 to 396 nm
Refractive Index 1.498 1.586 1.532 1.60-1.740
Abbe number 58 30 45 32-41
Specific Gravity 1.32 1.22 1.11 1.3-1.47
* Dispensing spectacles for children by Dr Eirian
Hughes

 Frame selection
◦ Small eye size frame
◦ Rounded shape
◦ Shape with small frame difference
◦ Adjustable nose pad
◦ Short vertex distance
◦ Cable or securely fitting temples

 Lens selection and Design
◦ High index plastic (since the lenses are heavy and
thick)
◦ Aspheric lenses (to counter spherical aberration )
◦ Lenticular lenses ( to counter heavy and thick lens)
◦ Light tints and UV protection (absence of inherent UV
absorption)
◦ Antireflection coating is must

• Consider increasing FOV by vertex reduction.
• Executive Bifocal lens desired but can do with ultex
or kryptop to increase near field of view design
reduce vertical prismatic effect.
• While marking in dummy lens make sure that bifocal
segment cuts child's pupillary margin.
• Less than 6 month old child do not need bifocal and
hence corrected for near.

• Smaller eye size
• Rounded corners
• Flatter or “hidden” bevels
• Full frame plastic frames- help
hide any edge thickness
• Avoid semi-rimless or rimless
frames

• Lenses selection :
• High index lens, aspheric, lenticulars
• Vertex distance close
• IPD can be matched or decentered based on
binocular status.
• Anti-reflection and hard coating.

 In children with ptosis use frames with lid crutches.
 In crouzans syndrome where eyes seems to be
popping out, face form lenses and frames with
reduced vertex distance may cause irritation to the
eyelids.
 In conditions like treacher Collin syndrome where
there is absent or maldeveloped ears use frames with
head band.

• Down’s syndrome- typically have a flat, broad bridge to their
nose
• standard nose fitting on that average spectacle frame tends not
fit properly.
• common sight to see a pair of glasses perched on the end of the
nose in Down’s syndrome.
• Metal frames are easier to adapt- more adjustable nosepieces.
• nosepieces can be manipulated and angled to fit the shape of a
flat nose better.
• slip-resistant pads to give a little more friction and stop the
frame moving so much.

• Have extreme photophobia
• May be associated with nystagmus, refractive errors,
strabismus and amblyopia
• Frames- hypoallergic and UV painted
• In albino children use colorful frame (esp. pink in girls) and any
suitable color frames for boys.
• Prescribe prescriptions tinted lens, photochromic lenses,
Polarized lenses and sunglasses with mirror coating.
• Incorporate prisms as per necessity

USE AVOID
Sturdy frames Lightly constructed copies
of adult frames
Deeply grooved frame fronts Frames with shallow grooves
Quality spring temples Nylon cord frames
High impact lenses such as
polycarbonate or Trivex
Any lenses that are not highly
impact resistant, especially glass
lenses
Sports protection when
applicable

 System of Ophthalmic Dispensing
 Borish Clinical Refraction
 Clinical Optics

Real Refractive error and spectacle correction.ppt

More Related Content

What's hot (20)

Similar to Real Refractive error and spectacle correction.ppt (20)

More from Bipin Koirala (20)

Recently uploaded (20)

Real Refractive error and spectacle correction.ppt

Editor's Notes