RETINOSCOPY

FARHANA ADNIN

B.OPTOM~2ND YEAR

ICO,CU.

WHAT ISOBJECTIVE REFRACTION ???

Where the result depends purely

on the examiners judgement to

determine the optimum optical

correction.

Methods for objective

refraction Keratometry

Ophthalmoscopy

Optometers

Auto refraction

Photorefraction

&

Retinoscopy [Most important & common

method ]

What is

Retinoscopy & Retinoscope?

Retinoscopy or skiascopy is the primary method for objective determination of the total refractive status of the eye.

Retinoscopy is done with the help of an instrument called Retinoscope.

It illuminates the inside of the eye,to observe the light that is reflected from retina.By examining how emerging rays change,refractive power of eye can be determined.

History~

Sir William Bowman in 1859,reported the movement of light and shadow effect.

Used since 1873 – reflecting mirror spot

retinoscopes, externally illuminated.

Modern streak design that brought

significant change in 1927, by Jack C.

Copeland.

INSTRUMENTATION

Head-light bulb

-peephole

-mirror

Neck

Sleeve-for rotating

Handle-electrical

supply

Techniques

2 main techniques of retinoscopy are :

1)Static Retinoscopy: It is the refractive state

determined when patient fixates an object at a

distance of 6m with accomodation relaxed.

2) Dynamic Retinoscopy: The refractive state

is determined while the subject fixates an

object at some closer distance, usually at or

near the plane of retinoscope itself with

accomodation under action.

Cont…

Static Retinoscopy include

Spot retinoscope: Light source is spot

of light.

Streak retinoscope: The bulb is

constructed so that is provides a beam

in the form of a streak rather than a

spot.

Spot retinoscope Streak retinoscope

Static Vs Dynamic Accomodation fully

relaxed

Working distance

lens added or

subtracted from

the objective finding

Fixates letters at 6m

Only ametropia or

emmetropia can be

determined

-Accomodation fully

in play

-No influence of

working distance

-Fixates at the bulb of

retinoscope

-Accomodative lag

can be determined

Significance ofspot & streak

Round filament Scoped in any

meridian Assessment of

the contact lensfitting

Dealing with pediatric patients

Vision screeningprograms

-Linear filament

-Quickly change

from plano mirror

to concave mirror

-Narrowing the

width makes it

easy to pin down

the principal

meridians

Principle of retinoscopy

To locate the far point of the eye/ plane

conjugate to the retina

Bring far point to the infinity by using

appropriate lenses

Accommodation at a minimum.

Continue......

Mirror with central hole

SubjectObserver

Incoming light

Outgoing light

Variable condensing lens

Origin of Retinoscopic Reflex

Interface between the vitreous and

retina.

Pigment epithelium of retina or

Bruch’s membrane

Stages of Retinocopy

Illumination stage

Projection stage

Reflection stage

Neutralization stage

Illumination Stage

Depends on ~

concept of the immediate source of light

the movement of the illuminated area of the fundus ,with the movement of reflecting mirror.

Plane mirror : immediate source of light moves with the movement of the mirror.

Concave mirror : immediate source of light moves against the movement of the mirror.

PROJECTION STAGE

1.Light source

2.Condensing lens

3.Mirror

4.Focusing sleeve

5.Current source

Reflex Stage

Depending upon the refractive status

of

the eye:~

Characteristics of reflex

1.Speed: large refractive errors have a

slow-moving reflex, small errors have a fast

reflex.

2.Brilliance: large errors have dull reflex,

small errors have a bright reflex. Becomes

brighter when neutrality approaches.

3)Width: Narrow in high degree error &

widen in low degree error.

Mirror effect… Plane mirror effect:

◦ Effective source lies behind the plane of mirror (most commonly used)

◦ The rays of light form the source goes parallel or slightly diverging

◦ Does not cross between the source and the patient’s eye- with movement – hyperopia

Against movement - myopia

Concave mirror effect:

◦ Generally not used

• keep the effective source in front of the plane

of the mirror, so that the rays emitted from

source are more converging and cross at a

certain distance between patient and the

source

with movement – myopia

Against movement - hyperopia

Concave mirror

effectPlane mirror effect

Working distance & lens

selectionBeginning retinoscopy, the examiner must

choose a WD.

Depends upon the length of the examiner’s

arm. If arm permits-

1. 66cm-WD=+1.50D

2. 50cm -WD=+2.00D

Prerequisite for

objective retinoscopyDark room

Retinoscope

A trial set

A trial frame

Distance fixation target

PROCEDURE~Patient sits at a distance of

66cm/50cm from the examiner.

~Patient is asked to fix at a distance

target to relax accommodation.

~Light is thrown on the patient’s

eye from retinoscope.

~By rocking the light slowly the

characteristics of the reflex

are observed.

~Then neutralizing the reflex.

~Examiner must be examined the

patient’s Rt eye by his/her Rt eye

& vice versa.

Nature of reflexes in ametropia

(plane mirror) Myopic far point of accommodation

located at a finite distance

infront of the eye

Hyperopes far point of

accommodation is located at

some point behind the

primary focal plane of the eye

• Emmetropic eyes far point

of accommodation is located

at infinity

Observation System• When we view the reflex in patient’s eye, it seems to

move in the direction

• If the retinoscope is tilted upward, reflex will move to the opposite direction ;in case of myope;

• same direction of retinoscopic light & reflex ; in case of hyperope and emmetrope;

• no movement (with working lens) at all in case of emmetrope.

Streak motion

Hyperopic patients

◦ Light focuses behind the retina

◦ Streak movement in

same direction as the

retinoscope . i.e.,

displays with motion

◦ Add plus lenses to bring

the focusing point up to the retina

Cont….

• Myopic patients–Light focuses at the point

before the retina

–Streak movement in

opposite direction as the

retinoscope

i.e., against movement

–Add minus lenses to move

the focal point back onto the retina.

Emmetropic patients

◦ No motion of the reflex observed in the

pupil

◦ Also known as neutral motion or complete

flashing

Spherical or Cylindrical ???

Streak both the

horizontal and vertical

meridian to determine

the astigmatism

Finding cylinder axis

1.Break: seen when the streak

is not parallel to the principal

meridian and disappears when

the streak is rotated to

the correct axis.

2. Width: reflex appears

narrowest when the streak

aligns with the axis.

3.Intensity: Line is brighter when the streak

is on the correct axis.

4. Skew: When the streak

is off-axis,it will move in a

slightly different dirrection

from the pupillary reflex

and move in the same

dirrection when the streak

is aligned with the principal

meridian.

Straddling:

Finding axis can be confirmed by this technique.

Performed with the estimated correcting cylinder in place.

Streak is turned 45⁰ off-axis in both dirrections.

If the axis is :Correct – widths should be equal in

both position.Incorrect – widths will be unequal.

Cont….

Finding the cylinder power

With 2 sphere : After the 2 principal meridians are

identified, spherical techniques are applied to each

axis.

With a sphere and a cylinder :

1st neutralize one axis by a spherical lens

↓

Over the lens,neutralize the other axis 90⁰

away by a cyliderical lens

Scissors reflex

When 2 band reflexes appear which move

towards & away from each other like the

blades of scissors….

Most of the time occurs in only one meridian

Seen in Keratoconus & irregular astigmatism

pt’s

.

◦ Neutralization~ ?

Neutralization point

Point at which the peephole becomes

conjugate with the patient’s retina.

Point at which the reversal of the

reflex is observed.

Neutralization . . .

With motion – Plus lenses are

added until neutrality occur.

Against motion – Minus lenses

are added…

The width of reflex widens progressively as

the neutralization is approached & at the

end point ~streak disappears~pupil completely

illuminated

End point of neutrality

1.Over correction of ±0.25D

2.On altering the WD.

3.Changing the mirror.

Clinical use…

Objective determination of refractive error

Starting point of subjective refraction

To find out regular & irregular astigmatism

Helpful for non-communicative or non-verbal pt’s

Screening for ocular disorders [keratoconus,

media opacities]

Some special assessments can be determined [Accommodation stability,Accommodative lag]

Errors of retinoscopy

1. Incorrect WD.

2. Failure of the patient to fixate the

distant target.

3. Scoping of the patient’s visual axis.

4. Failure to obtain a reversal.

5. Failure to locate the principal

meridians.

6. Failure to recognize scissors motion.

References…

Primary Care Optometry~ TheodoreGrosvenor

Clinical Procedures in Optometry~

Theory & Practice of Optics & Refraction~A.K.Khurana

Internet