ophthalmoscopy op1201 – basic clinical techniques posterior eye dr kirsten hamilton-maxwell
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OP1201 – Basic Clinical Techniques
Posterior eyeDr Kirsten Hamilton-Maxwell
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Today’s goalsBy the end of today’s lecture, you should be able to
explainWhy examining the posterior eye is importantBasic construction and optical principles of the direct
ophthalmoscopeHow to use it to examine the posterior eye and how to record
resultsHave some awareness of normal and abnormal posterior eye
conditionsLimitations of direct ophthalmoscopy
By the end of the related practical, you should be able toAssess and record the health of the posterior eye using direct
ophthalmoscopy efficiently and accurately
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OphthalmoscopyWe have used the direct ophthalmoscope to
examine the anterior eyeToday we will look at the primary function of this
device – examination of the posterior eyeFirst, we need to know how it works
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How ophthalmoscopy works (the optics)Ophthalmoscope construction – lens rack, aperture stops and
filtersBasic anatomy of the posterior eye
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Optics of the eye
Light from infinity enters the eye through the pupil and is focussed on the retina (in an eye with emmetropia only)
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Optics of the eye
If a light source could be placed on the retina, it would exit the eye along the same path
Light reflected from the retina behaves in the same way
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Optics of the eye
The light reflected from the retina would be seen by an observer located along the same axis
However, the observer would block the light source (why the pupil is black)
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Optics of ophthalmoscopy
Concave mirrorwith central hole(or semi-silvered mirror)
Light source at 90deg
Alternatively a prism
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Optics of ophthalmoscopy
Divergentlight, if subjecthypermetropic
Reflectedlight
source
Convergentlight, if subject
myopic
Divergentlight
Convergentlight
Parallellight
Focussedon retina
Corrective lens is placed along pathway
If clinician and patient are both emmetropic then:
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Lens rack powerIn order for reflected light exiting the patient’s
eye to be parallel, the patient’s ametropia (refractive error) must be corrected
In order for the parallel light entering the clinician’s eye to be focussed correctly, the clinician’s ametropia must be corrected
Need a corrective lens equal to sum of clinician’s and patient’s refractive errors
As individual subjects and observers have a range of refractive errors, need a range of lens powers (i.e. a lens rack)
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Ophthalmoscope headClinician Patient
Lens rack(~-20D to +20D)
Mirror (or May prism)
Variable brightnesslight source
Filters, aperture stops, miscellaneous
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Aperture stopsControl the size of the beamLarge, medium or small
Use largest for external and internal examination If pupils small, reduce aperture size
Use large or medium for internal examination
Use smallest for foveal examination
In general, use the largest beam possible for the best view
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FiltersRed-free filter
Blocks structures below Retinal Pigment Epithelium (RPE) and enhances contrast of retinal blood vessels and haemorrhages
Helps in cup to disc (C/D) ratio assessmentHelps identify nerve fibre layer (NFL) dropout – a
sign of glaucoma
Blue filterCan enhance reflectivity of optic disc drusenFor use with fluorescein/fluorescein angiography
Yellow filterReduces UV exposure
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MiscellaneousGraticule
Used in assessment of eccentric fixation
Determine relative size and distance of fundus structures
Slit beamHelps in assessment of 3-D
structures e.g. optic cup
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Basic ocular anatomyAnterior eyePosterior eye
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Posterior eye anatomy
Optic discMacula – no blood vessels, darker pigment than surrounding area
Blood vesselsVeins are darker than arteries, usually larger
Vessel crossing
Temporal Nasal
Retinal nerve fibre radiations
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Examining the posterior eye
Examples
Recording results
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How to do ophthalmoscopyAssume that the anterior eye examination has
just been completedThe lens power is +10DYou are 10cm away from the eyeThe patient is looking 15deg up and to their temporal
sideMedium to large aperture stop
First step is to locate the red reflex from the fundusWe are aiming to bring this into focus = retinal
structures visible
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What you seeDirect ophthalmoscopy gives an erect, real,
magnified image15x magnification with a 5deg field of view
through one eyeDepends on Rx
Higher magnification but smaller field of view for myopes Lower magnification but larger field of view for hypermetropes
Pupil size Better field of view with larger pupils BUT field of view is always small
No stereopsis
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What am I looking for?LensVitreousOptic disc
SizeC/D ratioMarginsColour
Blood vesselsA/V ratioCrossingsCalibre/tortuosityReflectivityLeakage
MaculaWhole areaFovea and foveal reflex
PeripheryRetinaChoroid
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How to view the lens
Retro-illumination
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VitreousGet as close to your patient’s eye as you canWith the red reflex visible, reduce lens rack
power by 1D steps (towards zero, or plano)As you do this, you will focus at different depths
within the vitreous until finally the fundus comes into focus
If you and your patient are both emmetropic and not accommodating (almost impossible when you are learning), the lens power should be zero when you are in focus
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Vitreous floaters
Will look like a dark shadow among the red/orange reflexWill move when the patient moves their eyes
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Scan the fundusBe systematicUse the disc as an orientation pointIf the patient is looking 15deg to the temporal
side and you move in along the horizontal visual axis, you should find it straight away
All of the blood vessels originate in the disc, so follow them from here. If you get lost, return to the disc and start again
Ask the patient to look in the 9 cardinal directions to assess the periphery
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Make sure no gaps in fundus coverage: when following vessels, scan perpendicularly.Scan from arcades towards fovea.
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Blood vesselsLook for
Calibre – vessel width and regularityTortuosity – “wriggliness” of vesselsArtery/Vein (A/V) ratio
Compare width of artery (red) to vein (darker red) Should be about 2/3
Crossings Does the vein change shape when crossed by an artery?
Can be compressed leading to nipping
Reflectivity – is the vessel sheath clear or opaque?Leaking – haemorrhages, exudates
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Normal vessels
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More normal vessels
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Abnormal blood vessels
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More abnormal blood vessels
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RetinaSometimes the word “retina” is used to mean the
same thing as “fundus”Anatomically, the retina is a transparent layer
containing photoreceptors and connecting cellsThe retinal interface with the vitreous may reflect
light like a wet surface, but you will not usually see the retina itself unless there is a problem
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Retina
Myelinated nerve fibres
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Retina
Retinal detachment
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MaculaCones onlyFovea in the centreMore pigmented than surrounding retinaNo blood vessels
Supplied by the underlying choroid and choriocapillaris
Ask the patient to look directly into the light In young healthy eyes, you will see a yellow
reflection = foveal reflex Note its presence and whether it is bright,
moderate or dim Use graticule to assess centrality of the
fovea
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Normal macula
Darker at macula
Note: This is also a tigroid fundus… choroidal blood vessels are visible (view usually blocked by the RPE)
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Macula disease
ARMD - drusen
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Recording ophthalmoscopySize and distance is
recorded in terms of disc diameters
Direction is recorded according to a clockface in hoursDo not flip for RE and
LE
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Locating a lesion - example
This lesion is1DD wide,
0.5DD high1DD above the
foveaOR 3DD from
the disc at 10 o’clock
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Recording your findings
The area you can see with the direct
ophthalmoscope
Disc
MaculaClock directions
Disc – for next week
39 39
Use descriptive termsWrite something for
everything!
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Dropout in glaucoma,myelination at disc margin.
Crossings: nipping insystemic hypertension
Cupping and notchingin glaucoma
Swelling and blurredmargins in papilloedemaand optic neuritis
Vessel walls: sheathing in systemic hypertension, leakage and neovascularisation in diabetes.
Bifurcations: embolisms,branch occlusions
Pigmentation changesin retinitis pigmentosa
Haemorrhagesin diabetes, vessel occlusion,hypertension
Myopic crescentin myopia
ARMD, drusen,macular holes
Retinal tears,detachments
Anterior ischaemic opticneuropathy in diabetes
Vessels
Optic disc
Fovea
Background/periphery
Retinal nerve fibre layerTumours
Vitreous
Asteroid hyalosis, floaters,haemorrhages
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LimitationsNo stereopsisSmall field of view
Not all of the fundus covered, even by a thorough systematic technique
Large lesions can be missed entirely, especially if the colour change is gradual
Cannot see very far into the peripheryIndirect ophthalmoscopy is preferred for fundus
examination
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Elliott, Sections 6.4 to 6.5, 6.20Become familiar with the procedural steps
Memorise anatomical structures