1. Ophthalmoscopy OP1201 – Basic Clinical Techniques Posterior eye
Dr Kirsten Hamilton-Maxwell

2. 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

3. 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

4. The science How ophthalmoscopy works (the optics)
Ophthalmoscope construction – lens rack, aperture stops and filters
Basic anatomy of the posterior eye

5. 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)

6. 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

7. 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)

8. Optics of ophthalmoscopy
Concave mirror
with central hole
(or semi-silvered mirror)
Alternatively a prism
Light source at 90deg

9. Optics of ophthalmoscopy
If clinician and patient are both emmetropic then:
Divergent
light
Convergent
Parallel
Focussed
on retina
Reflected
light
source
Corrective lens is
placed along pathway
Divergent
light, if subject
hypermetropic
Convergent
light, if subject
myopic

10. 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)

11. Filters, aperture stops,
Ophthalmoscope head
Clinician
Patient
Lens rack
(~-20D to +20D)
Mirror (or May prism)
Filters, aperture stops,
miscellaneous
Variable brightness
light source

12. 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

13. Filters Red-free filter Blue filter Yellow 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

14. Miscellaneous Graticule Slit beam
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

15. Basic ocular anatomy
Posterior eye
Anterior eye

16. Posterior eye anatomy Vessel crossing Retinal nerve fibre radiations
Macula – no blood vessels, darker pigment than surrounding area
Nasal
Temporal
Optic disc
Everything enters through the same place – the optic nerve head. Retinal fibres should be transparent.
Blood vessels
Veins are darker than arteries, usually larger

17. Procedure
Examining the posterior eye
Examples
Recording results

18. 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

19. 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

20. What am I looking for? Lens Vitreous Optic disc Blood vessels Macula
Size
C/D ratio
Margins
Colour
Blood vessels
A/V ratio
Crossings
Calibre/tortuosity
Reflectivity
Leakage
Macula
Whole area
Fovea and foveal reflex
Periphery
Retina
Choroid

21. How to view the lens
Retro-illumination

22. 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

23. Vitreous floaters
Will look like a dark shadow among the red/orange reflex
Will move when the patient moves their eyes

24. 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

25. Scan from arcades towards fovea.
Make sure no gaps in fundus coverage: when following vessels, scan perpendicularly.
Scan from arcades towards fovea.

28. 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

29. Normal vessels

30. More normal vessels

31. Abnormal blood vessels

32. More abnormal blood vessels

33. 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

34. Retina
Myelinated nerve fibres

35. Retina
Retinal detachment

36. 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

37. Normal macula Darker at macula
Note: This is also a tigroid fundus… choroidal blood vessels are visible (view usually blocked by the RPE)

38. Macula disease
ARMD - drusen

39. 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

40. 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

41. Recording your findings
Disc – for next week
Clock directions
Macula 3 9 3 9
Disc
This is similar to the anterior eye diagrams that I introduced last week, with graphical and text recording
The area you can see with the direct ophthalmoscope
Use descriptive terms
Write something for everything!

42. Background/periphery
Vitreous
Pigmentation changes
in retinitis pigmentosa
Asteroid hyalosis, floaters,
haemorrhages
Retinal tears,
detachments
Retinal nerve fibre layer
Tumours
Dropout in glaucoma,
myelination at disc margin.
Vessels
Fovea
Haemorrhages
in diabetes,
vessel occlusion,
hypertension
ARMD, drusen,
macular holes
Optic disc
Myopic crescent
in myopia
Crossings: nipping in
systemic hypertension
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

43. Limitations

44. 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

45. Further reading Elliott, Sections 6.4 to 6.5, 6.20
Become familiar with the procedural steps
Memorise anatomical structures