RETINOSCOPY

DR. ANKUSH WEGINWAR

RETINOSCOPY

Introduction History Types of retinoscope Far point Optical principle Types of retinoscopy Problems in retinoscopy

Introduction

An accurate objective measurement of the refractive state of an eye can be made using the retinoscope

The technique is called retinoscopy

Pupilloscopy, shadowscopy, skiascopy, umbrascopy, scotoscopy,korescopy

Histroy

1859 Bowman introduced

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

1927, Copeland -streak retinoscope

Types of Retinoscopes

Reflecting mirror retinoscope

Self illuminated retinoscope

Plane mirror Spot retinoscope

Priestley-smith’s mirror(plane and concave mirrors)

Streak retinoscope

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

Advantage Cheaper than Self illuminated

Disadvantage Requires a separate light source Glare from the source of light is annoying to the patient To check the axis and amount of cylinder is difficult Intensity and type of beam cannot be changed or controlled

Self illuminated retinoscope

The light source and the mirror are incorporated in one

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

Streak Retinoscope

Two operating system Projecting system Observation system

Projecting system

Main purpose: To illuminates the retina

Contsists of: Light source Condensing lens Mirror Focusing sleeve Current source

Projecting System

Copeland streak retinoscope:

All the way up, plane mirror is in position with a wide streak.As it is lowered gradually , the streak decreases in width.

And widens again.At the lowest adjustment the streak is again at its maximum width but with concave mirror effect.

Usual method of vergence control (lens is fixed)

Projecting System

American Optical and Welch Allyn: These instruments are in plane mirror mode

when the mechanism is all the down rather than all the way up

Alternative method Vergence control (bulb is fixed)

Observation system

Main purpose: To allows the observer to see the retinal reflex of the patient.

Streak retinoscope

Advantages Self illuminated (light source and mirror are incorporated in one) Easily manipulated and the intensity and the type of beam can be easily controlled

Advantages of Streak Retinoscope over Spot Retinoscope Exact axis of cylinder power can be found easily by streak retinoscope In high refractive errors by using concave mirror effect we can find the amount of refractive error By using enhancement technique we can estimate the gross amount of hyperopia up to 5D Or over 5D

Far point

The far point of eye is defined as the point in space that is conjugate with the fovea when accomodation is relaxed

Emmetropia Parallel rays focus on fovea Retina conjugate with infinity Far point is at infinity

Hypermetropia Parallel rays focus behind retina Far point is beyond infinity Plus lens converges rays on to retina and conjugate fovea with infinity

Far point

Myopia Parallel rays focus infront of retina Far point is between infinity and eye Minus lens diverges rays on to the retina and conjugate fovea with infinity

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

PRE-REQUISITES-a. Semi-dark Roomb. Trial setc. Lens Rack d. Trial Framee. Phoropter or Refractorf. Fixating targets [distance & near charts, illuminating source]

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

A light source is located beside the patient's head, and light reflected into the patient's eye from a plane or concave mirror held by the observer.

The observer views the patient's eye through a small hole in the mirror. The electric retinoscope has largely replaced this system. However, the

principles and nomenclature have remained unchanged. When a plane mirror is used, light is moved across the patient's fundus

from A to B by rotating the plane mirror from M1 to M2. Note that the illuminating rays move in the same direction as the mirror.

A concave mirror of focal length less than the distance between patient and observer is occasionally used for retinoscopy. A real image of the light source is formed

Reflex Stage

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

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

Working Distance This is the distance at which the eye is focused when the reflex has been neutralized

In other words, the eye on which you just performed retinoscopy has 1.50 D of plus-powered sphere more than it needs unless you want to measure visual acuity at 66 cm

If the distance is between 54 and 61 cm, use 1.75 D as your working lens.

Those with a working distance between 62 and 72 cm should use 1.50 D

To allow the eye to focus at 20 feet (6 m), this power must be taken away from the gross retinoscopy result.

This is done by dialing 1.50 D toward the minus, also known as “removing the working lens’’

“Retinoscopy lens” built into most refractors; the lens is inserted prior to performing retinoscopy and simply removed at the completion

Fundal reflex

The streak reflex is a diffuse reflection of light from the illuminated fundus:an elongated patch of fundus that becomes the illuminated object for refraction out of the eye.

Properties of the fundal reflex indicate the refractive status of the eye Brightness direction of motion speed of motion Width

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 Retinoscopic Fundus Reflex

No movement of red reflex indicates myopia of 1D

With movement-it indicated that the far point was behind the retinoscope aperture, in the continuum between the operator and infinity (slightly myopic and emmetropic eyes) or behind the eye (hyperopic eyes)

In the case of "with" motion, lenses of progressively more plus refractive power must be inserted at the spectacle plane for neutrality to be achieved

"Against" motion of the streaindicated that the far point was between the retinoscope aperture and the patient's eye (moderately to highly myopic eyes)

In the case of "against" motion, lenses of progressively more minus refractive power must be inserted at the spectacle plane for neutrality to be achieved

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

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 axis Break

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. The band of light in pupillary area lies in a position intermediate between the band outside the pupil and that from axis of the cylinder.

The axis even in the case of low astigmatic error can thus be determined by rotating the streak until the break disappear. The correcting cylinder should placed at this axis.

The oblique axis can be determined by rotating the streak until the break disappears.

Finding the cylinder axis Skew

Skew means oblique motion of the steak reflex

Skew may be used to refine the axis in small cylinders

The streak and reflex will move in the same direction only when streak is aligned with one of the principal meridian

Therefore if the streak is not aligned with the true axis skewing will be observed on movement of the steak

Straddling CONFIRMATION OF THE AXIS

This is performed with approximately correct cylinder in place

Straddling

The streak is turned 45 degree off axis in both directions

If the axis is correct, the width of the reflex should be equal in of the two positions

If the axis is not correct, the widths will be unequal in the two position. In such a situation the narrower reflex serves as the guide towards which the cylinder axis should be turned

Finding the cylinder power

3 Methods

With two spheres With a sphere and cylinder With two cylinders

With two spheres

First neutralize one axis with appropriate sphere Then keep on changing the sphere till the second axis is neutralized Astigmatism is measured by the difference between the 2 spheres

With a sphere and cylinder

First 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

Enhancement

This 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

Enhancement

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

End point of retinoscopy

NeutralThe end point of retinoscopy means neutralisation of red reflex in any meridian with the movement of the mirror

ReversalThe real endpoint for retinoscopy

Overcorrection by 0.25D should cause reversal of the movement

Slight forward movement should cause ‘with movement’

Slight backward movement should cause ‘against movement’

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

Types of retinoscopy

Wet retinoscopy- with cycloplegic retinoscopy is performed

Dry retinoscopy-without cycloplegic

Indications for wet retinoscopy

Accommodative 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

Atropine sulphate 1% Cyclopentolate 1% Homatropin 2%

Wet Retinoscopy

Disadvantages Temporary 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

Patient 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

Problems in retinoscopy

Retinoscopy in nuclear cataract shows index myopia in early stages

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

Retinal 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 reading

Inexperience Not aligning with Visual axis of the patient Definite working distance is not maintained Lack of subject’s accommodation Defect in trial lenses Lack of patient’s co-ordination