Transcript Ophthalmoscopy - Optometry Peer Tutoring

Ophthalmoscopy
OP1201 – Basic Clinical Techniques
Posterior eye
Dr Kirsten Hamilton-Maxwell
Today’s goals
 By the end of today’s lecture, you should be able to
explain
 Why examining the posterior eye is important
 Basic construction and optical principles of the direct
ophthalmoscope
 How to use it to examine the posterior eye and how to record
results
 Have some awareness of normal and abnormal posterior eye
conditions
 Limitations of direct ophthalmoscopy
 By the end of the related practical, you should be able to
 Assess and record the health of the posterior eye using direct
ophthalmoscopy efficiently and accurately
Ophthalmoscopy
 We have used the direct ophthalmoscope to
examine the anterior eye
 Today we will look at the primary function of this
device – examination of the posterior eye
 First, we need to know how it works
The science
How ophthalmoscopy works (the optics)
Ophthalmoscope construction – lens rack, aperture stops and
filters
Basic anatomy of the posterior eye
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)
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
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)
Optics of ophthalmoscopy
Concave mirror
with central hole
(or semi-silvered mirror)
Alternatively a prism
Light source at 90deg
Optics of ophthalmoscopy
If clinician and patient are both emmetropic then:
Focussed
on retina
Convergent
light
Corrective lens is
placed along pathway
Parallel
light
Divergent
light
Convergent
light, if subject
myopic
Divergent
light, if subject
hypermetropic
Reflected
light
source
Lens rack power
 In 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)
Ophthalmoscope head
Clinician
Patient
Mirror (or May prism)
Filters, aperture stops,
miscellaneous
Lens rack
(~-20D to +20D)
Variable brightness
light source
Aperture stops
 Control the size of the beam
 Large, 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
Filters
 Red-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 assessment
 Helps identify nerve fibre layer (NFL) dropout – a
sign of glaucoma
 Blue filter
 Can enhance reflectivity of optic disc drusen
 For use with fluorescein/fluorescein angiography
 Yellow filter
 Reduces UV exposure
Miscellaneous
 Graticule
 Used in assessment of eccentric
fixation
 Determine relative size and
distance of fundus structures
 Slit beam
 Helps in assessment of 3-D
structures e.g. optic cup
Basic ocular anatomy
Posterior eye
Anterior eye
Posterior eye anatomy
Retinal nerve fibre radiations
Macula – no
Temporal
blood vessels,
darker pigment
than surrounding
area
Vessel crossing
Nasal
Optic disc
Blood vessels
Veins are darker than
arteries, usually larger
Procedure
Examining the posterior eye
Examples
Recording results
How to do ophthalmoscopy
 Assume that the anterior eye examination has
just been completed
 The lens power is +10D
 You are 10cm away from the eye
 The patient is looking 15deg up and to their temporal
side
 Medium to large aperture stop
 First step is to locate the red reflex from the
fundus
 We are aiming to bring this into focus = retinal
structures visible
What you see
 Direct ophthalmoscopy gives an erect, real,
magnified image
 15x magnification with a 5deg field of view
through one eye
 Depends 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
What am I looking for?
 Lens
 Vitreous
 Optic disc
 Size
 Macula
 Whole area
 Fovea and foveal reflex
 Periphery
 C/D ratio
 Retina
 Margins
 Choroid
 Colour
 Blood vessels
 A/V ratio
 Crossings
 Calibre/tortuosity
 Reflectivity
 Leakage
How to view the lens
Retro-illumination
Vitreous
 Get as close to your patient’s eye as you can
 With 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
Vitreous floaters
 Will look like a dark shadow among the red/orange reflex
 Will move when the patient moves their eyes
Scan the fundus
 Be systematic
 Use the disc as an orientation point
 If 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
Make sure no gaps in fundus coverage: when following vessels, scan perpendicularly.
Scan from arcades towards fovea.
Blood vessels
 Look for
 Calibre – vessel width and regularity
 Tortuosity – “wriggliness” of vessels
 Artery/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
Normal vessels
More normal vessels
Abnormal blood vessels
More abnormal blood vessels
Retina
 Sometimes the word “retina” is used to mean the
same thing as “fundus”
 Anatomically, the retina is a transparent layer
containing photoreceptors and connecting cells
 The 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
Retina
Myelinated nerve fibres
Retina
Retinal detachment
Macula
 Cones only
 Fovea in the centre
 More pigmented than surrounding
retina
 No 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
Normal macula
Darker at macula
Note: This is also a tigroid fundus… choroidal blood vessels
are visible (view usually blocked by the RPE)
Macula disease
ARMD - drusen
Recording ophthalmoscopy
 Size and distance is
recorded in terms of
disc diameters
 Direction is recorded
according to a
clockface in hours
 Do not flip for RE and
LE
Locating a lesion - example
 This lesion is
 1DD wide,
0.5DD high
 1DD above the
fovea
 OR 3DD from
the disc at 10
o’clock
Recording your findings
Disc – for next week
Clock directions
9
The area you can see
with the direct
ophthalmoscope
3
9
Macula
Disc
Use descriptive terms
Write something for
everything!
3
Background/periphery
Vitreous
Pigmentation changes
in retinitis pigmentosa
Asteroid hyalosis, floaters,
haemorrhages
Retinal tears,
detachments
Retinal nerve fibre layer
Dropout in glaucoma,
myelination at disc margin.
Tumours
Vessels
Fovea
Haemorrhages
in diabetes,
vessel occlusion,
hypertension
ARMD, drusen,
macular holes
Crossings: nipping in
systemic hypertension
Optic disc
Myopic crescent
in myopia
Cupping and notching
in glaucoma
Bifurcations: embolisms,
branch occlusions
Anterior ischaemic optic
neuropathy in diabetes
Vessel walls: sheathing in
systemic hypertension, leakage
and neovascularisation in diabetes.
Swelling and blurred
margins in papilloedema
and optic neuritis
Limitations
Limitations
 No stereopsis
 Small 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 periphery
 Indirect ophthalmoscopy is preferred for fundus
examination
Further reading
Elliott, Sections 6.4 to 6.5, 6.20
Become familiar with the procedural steps
Memorise anatomical structures