retinoscopy and its principles

Retinoscopy and its principles

Presenter : Dr.Rasika Thakur Moderator: Dr.Monica Samant

Mr.Kunal Kishor

IntroductionHistoryTypes of retinoscopeFar pointOptical principleTypes of retinoscopyProblems in retinoscopy

Introduction An accurate objective measurement of the

refractive state of an eye can be made using the retinoscope

The technique is called retinoscopyPupilloscopy, shadowscopy, skiascopy,

umbrascopy, scotoscopy

History

• 1873,F.Cuigent the father of retinoscopy- first described a retinoscope

1878, M. Mengin

1880, H. Parent - retinoscopie

• 1927, Copeland -streak retinoscope

Types of retinoscopes

Reflecting mirror retinoscope• A perforated mirror by which the beam is

reflected in to the patients eye and through a central hole the emergent rays enter the observer’s eye

• Movements of the illuminated retinal area are produced by tilting a mirror, either a plane or concave

Reflecting mirror retinoscope

Reflecting mirror retinoscope contd…

Self illuminated retinoscope

• The light source and the mirror are incorporated in one

• STREAK RETINOSCOPE- Light source is a linear (uncoiled) filament

Streak Retinoscope

Projecting system

Main purpose:

To illuminates the retina Contsists of:

• Light source• Condensing lens• Mirror • Focusing sleeve• Current source

Projecting system of Copeland type.

Projecting system of Welch Allyn.

....

.

Observation systemMain purpose:

To allows the observer to see the retinal reflex of the patient.

Streak Retinoscope

Advantages of Streak Retinoscope over Spot Retinoscope

Far point • The far point of eye is defined as the point in

space that is conjugate with the fovea when accomodation is relaxed

Far point contd…

Optical Principle

• Retinoscope works on Focault's principle• Retinoscopy is based on the fact that when light

is reflected from a mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive state of the eye

Optical Principle• The illumination stage• The reflex stage • The projection stage

Illumination StageLight is directed into the patient's eye to illuminate the retina

Reflex Stage

An image of the illuminated retina is formed at the patient's far-point

Exercises in Refractometry.Thorofare, NJ: SLACK Incorporated; 1990

Projection Stage

The image at the far-point is located by moving the illumination across the fundus and noting the behaviour of the luminous reflex seen by the observer in the patient's pupil

Emmetropic eye

Hypermetropic eye

Myopia of less than 1D

Myopia of 1D

Myopia of more than 1D

Projection Stage

Working Distance

• The distance from the retinoscope to the patient’s eye

• D = 1 ÷ F• The length of the average person’s arm is

66 cm. The power of a lens that focuses parallel light rays at 66 cm is +1.50 D

Should I use a “working lens” to compensate for the working distance?

Advantages-Instant identification of myope or hyperope.Working lens might help relax accommodation.No need for mental arithmetic to allow for

working distanceDisadvantages-

Too much blur does not necessarily relax accommodation.

Working lens adds extra reflections to the view.

Formation of the Secondary Fundus Source or "Fundus Reflex"

• Light reflected from the fundus has two components:• A diffuse component, which is also called

backscatter• A directed component

Fundal reflex

Properties of the fundal reflex indicate the refractive status of the eye

• Brightness• direction of motion• speed of motion• Width

Brightness of the Retinoscopic Fundus Reflex

The brightness of the fundus reflex is greatest when the retinoscope aperture coincides with the far point of the eye

In highly myopic and highly hyperopic eye the pupillary reflex appears dim

Direction of Motion of the RetinoscopicFundus Reflex

No movement of red reflex indicates myopia of 1D

Contd..

• Red reflex moves along with the movement of the retinoscope, it indicate emmetropia or hypermetropia or myopia of less than 1D.

Contd..

• A movement of red reflex against the movement of the retinoscope, indicates myopia of more than 1D.

Speed and width of the Retinoscopic Fundus Reflex

• Indicates that how far we are from neutrality• A slow moving streak reflex - long way from

neutrality.

Finding the cylinder axis

• In the presence of astigmatism, one axis is neutralized with the spherical lens & the second axis still shows the movement of reflex in the direction of axis of astigmatism

Finding the cylinder axisBreak

Break in the alignment between the reflex in the pupil and the band outside it is observed when the streak is not parallel to one of the meridian

Finding the cylinder axis Skewif the streak is not

aligned with the true axis oblique motion of streak reflex will be observed on movement of the steak.

StraddlingCONFIRMATION OF THE AXIS•This is performed with approximately correct cylinder in place

Finding the cylinder power

3 Methods-

With two spheresWith a sphere and cylinderWith two cylinders

With two spheresFirst neutralize one axis with appropriate sphereThen keep on changing the sphere till the second axis

is neutralizedAstigmatism is measured by the difference between

the 2 spheres +2.00D

+3.00D + 2.00Ds / + 1.00 Dc X 900

With a sphere and cylinderFirst neutralize one axis with an appropriate

spherical lens.Neutralize the other axis with a cylindrical

lens at the appropriate orientation The spherical cylindrical gross retinoscopy

may be read directly from the trial lens apparatus

EnhancementThis technique is to approximately estimate the

amount of refractive error with minimal use of trial lenses.

If the reflex inside pupil gets more thinner by changing the sleeve width,it suggests a significant refractive error

Thinnest retinal reflex is called Enhanced band

EnhancementA rough estimation of the refractive error is possible,based on the sleeve position

End point of retinoscopy

Types of retinoscopy• Static Retinoscopy: the patient is looking at a

distant object, with accommodation relaxed.

• Dynamic retinoscopy: the patient is looking at a near object, with accommodation active.

• Near retinoscopy: the patient is looking at a near object, with accomodation relaxed

Dynamic Retinoscopy Techniques

MEM Retinoscopy

Help to calculate patients lag or lead of accomodationLettered targets are applied to the head of a

retinoscope Fixation target is placed at harmon

distance/50 cm with patients corrected refractive error

the refractive power of the trial lens that brings neutrality is the accommodative lag/lead

Nott’s method

It determines lag/lead of accomodation by moving retinoscopic apperture towards or away from the eye

Target is the letters around the aperture of a near point card

At a distance of 40 cmThe accommodative response, in diopters, is

subtracted from the accommodative demand,to determine the accommodative lag/lead

Bell Retinoscopy

The retinoscope remains in a fixed position and the target is moved

The retinoscopy is performed from a fixed distance of 50 cm

The distance between the retinoscope and the target when the change in motion occurs is a physical measure of the lag/lead of accommodation

Near retinoscopy /Mohindra retinoscopy

Also known as near monocular retinoscopyEstimate the refractive status of the eyeThe stimulus or fixation is the dimmed light

source of the retinoscope in a darkened room

The retinoscope is held at a distance of 50cm with hand-held trial lenses

Borish's Clinical Refraction. 1998. WJ Benjamin. WB Saunders Company. Philadelphia, London, Toronto.

Radical retinoscopy

Done in patients with small pupils, cataract, or any other opacity

Working distance here is 20cm or even less upto 10cm

Chromoretinoscopy Helps in a clinical measurement of the

chromatic aberration of an eyeTransmittance filters with selected dominant

wavelengths, are placed in the light path between the light source of a retinoscope and the retinoscopist's eye

Types of retinoscopy

• Wet retinoscopy- with cycloplegic retinoscopy is performed

• Dry retinoscopy-without cycloplegic

Indications for wet retinoscopyAccommodative fluctuations indicated by a

fluctuating pupil size and/or reflex during retinoscopy

Patients with esotropia or convergence excess esophoria

A retinoscopy result significantly more positive or minus (>1.00 DS) than the subjective result

cycloplegic drugs used in wet retinoscopy

Atropine sulphate 1%Cyclopentolate 1%Homatropin 2%

Disadvantages of cycloplegic retinoscopyTemporary symptoms of blurred vision and

photophobia The degradation of vision is caused by the

abolition of the accommodation response Increase in ocular aberrations as a result of

dilated pupils.Adverse effects and allergic reactions to

cyclopentolate are rare

Problems in retinoscopy

• Red reflex may not be visible -small pupil, hazy media & high degree of refractive error

• Scissoring shadow-may be seen in healthy cornea but with unusual difference in curvature in the centre & the corneal opacities

contdPatient with strabismus-it is easier to change

the fixation of good eye so that retinoscopy can be performed along the visual axis of the strabismic eye

Retinoscopy in nuclear cataract shows index myopia in early stages

contd

• Spherical aberrations -lead to variation of refraction in the centre & periphery of pupil. It may be seen in normal eyes but more marked in lenticular sclerosis.

• Conflicting shadows- moving in various directions in different parts of the pupillary area with irregular astigmatism

• Triangular shadow- may be observed in patients with conical cornea

Non-refractive uses of retinoscopy

Opacities in the lens and iris -dark areas against the red background

Extensive transillumination defects in uveitis or pigment dispersion syndrome -bright radial streaks on the iris

Keratoconus distorts the reflex and produces a swirling motion

contdRetinal detachment involving the central area

will distort the reflecting surface and a grey reflex is seen

A tight soft contact lens will have apical clearance in the central area which will cause distortion of the reflex

Reason for false readingInexperience Not aligning with Visual axis of the patient Definite working distance is not maintainedLack of subject’s accommodationDefect in trial lensesLack of patient’s co-ordination

Thankyou