7. A Bit History……
Jan Purkinje (Latin -1823) - Complete technique of
ophthalmoscopy
Next 25 years: Kussmaul, Cumming, Brucke, and
Babbage worked on the ophthalmoscope
1851 Helmholtz - First useable direct
ophthalmoscope
8. The modern ophthalmoscope
Here light source from the
batteries is reflected at 90o
using a mirror placed in the
head portion at 45o angle.
The examiner looks through
a hole in the mirror that is
through the light.
9. Characteristics of the image
Virtual, erect and magnified Image.
Field of view ~ 10°
To enlarge field of view examiner’s eye must be closer to patient’s eye with patient’s pupils
dilated
Enlargement capacity of any magnification lens = 1/4th of lens power
Retinal image in emmetropic eye (60 D)- magnified by 60/4, or ×15
In aphakic eyes (20 D natural lens removed )
=magnification for the observer is reduced to about 40/4 or ×10.
Hyperopic eye of +10D ---power of eye= 50D
Thus magnification = 50/4= X 12.5
Myopic eye of -10D---power of eye= 70D
Thus magnification = 70/4= X 17.5
11. Instrumentation
Direct Ophthalmoscope
Illumination system & observation system
Illumination system
Light source
condensing lenses
reflecting prism
an aperture
Observation system –
Peephole
bank of spherical lenses
Lens strength selector
wheel
Bulb in here
Concave mirror
with a hole in
centre
Selects light
size, filter &
grid
Connects to
rheostate and
handle containing
batteries
15. Emergent rays from the fundus of the observed eye (O1)
showing formation of retinal image on retina of observer's
eye (02)
In emmetropia (E) - emergent parallel rays are brought to a
focus on the retina of 02 if the accommodation of this eye is
absolutely at rest.
16. In hypermetropia (H)- the emerging divergent
rays are brought to a focus on the retina of 02,
either by means of accommodation or by
placing a convex lens in front of 02.
17. In myopia, M, the emergent convergent
rays can only be brought to a focus on the
retina of 02 by placing a concave lens in
front of 02.
18. Methods of Ophthalmoscopy
Distance direct ophthalmoscopy
Illuminating eye from 25-40
inches
Direct ophthalmoscopy
Approach closer to patient.
19. Procedure
Of Direct Ophthalmoscopy…
Set the patient in a semi dark room & instruct to look at a distant target.
Hold ophthalmoscope in right hand and look through examiner’s right eye at
patient’s right eye
Examine for red reflex at arm’s length (20-40cm)
Normal - red glow from choroid
Look for opacities or loss of reflex
The examiner moves as close as to the patient to examine anterior segment
with high + power (+10D to +13D)
20. Cont…
Then by reducing + power, crystalline, lens, vitreous & finally the optic nerve
head can be observed.
Optic disc is visualized first & blood vessels can be followed then.
After quadrant by quadrant scan of fundus, the macula is examined.
…left eye…
22. Advantages
It is relatively easy procedure to master as compare to
IO.
IT has the greatest amount of magnification of any
procedure used for fundus examination.
By using the lens wheel to adjust focus, the clinician is
able to examine the various structures of the eye.
It can be used in non dilated pupil.
It is portable.