Upload
laxmi-eye-institute
View
9.750
Download
140
Embed Size (px)
DESCRIPTION
Retinoscopy and its principles
Citation preview
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