2. • Objective method of examining the posterior
segment of the eye.
• Presence or absence of abnormalities in the
posterior segment - structural or pathological.
• View of vascular & neurological structures of a living
organ in-situ.
Introduction
3. Types
• Can be divided into two types :
– Direct ophthalmoscope
– Indirect ophthalmoscope
7. Optics
• A convergent beam of
light is reflected into
the patient’s pupil.
• The emergent rays
from any point on the
patient’s fundus reach
the observer’s retina
through the viewing
hole in the
ophthalmoscope.
8. Optics (In Hyperopic patient’s)
• In a hypermetropic
patient’s, the emergent
ray from the illuminated
area of retina will be
divergent & thus can be
brought to focus on the
observer’s retina if the
latter accommodates,
or by the help of a
convex lens
9. Optics (In Myopic patient’s)
• In a myopic patient’s
the emergent rays will
be convergent & thus
can be brought to
focus on the observer
retina by the help of a
minus lens
11. Illuminating system
• Illuminating system consists of:
- Tungsten bulb
- Condenser system
- Lens
- Reflector (half silvered mirror)
- Aperture stops and filters (between condensing
lens and projection lens)
12. Illuminating system
• Filters
- Red-free filter (green)
- Blue filter
Green filter
• Increases the contrast between retinal vessels and the
background
• To differentiate between retinal and choroidal lesions.
13. Illuminating system
• Nerve fibre layer of the retina.
• Early dropout of the nerve fibre layer.
• Enhance the estimation of CD ratio.
Blue filter
• Enhances the visibility of fluorescein for use in FFA.
16. viewing system
• It consists of 3 aperture stops :
1) Small - for macula
2) Intermediate - for viewing the fundus through
normal pupils
3) A large - to view through dilated fundus.
17. viewing system
• Slit diaphragm - observing elevated retinal
lesions.
• Half circle - reduces reflection by limiting the
illumination & observing certain fine retinal
details.
• Fixation star - to determine patients fixation in
strabismic amblyopia.
18. Half circle
Small aperture
Intermediate aperture
Fixation star
Slit aperture
Filter changing lever
Green filter
Large aperture
Sight hole
Blue filter
Aperture stop
19.
20. Characteristics of image formed
• In direct
ophthalmoscope the
image is ERECT,
VIRTUAL, & about 15
times MAGNIFIED
• Field of view is 5*
from the fixn. point
22. Field of vision
• Directly proportional to the size of the pupil of
observed eye
• Directly proportional to the axial length of the
observer’s eye
• Inversely proportional to the distance between the
observer’s & observed eye
• The smaller the sight hole of ophthalmoscope the
better the field of vision
23. Technique
• Patient seated in semi-dark room & looking straight
ahead
• Pt. right eye should be examined by the observer
with his right eye & left with the left
• Once the red reflex is seen, the observer should
move as close to the patient’s eye as possible
(theoretically at the antr. focal plane of the pt. eye
i.e. 15.4mm)
24. Clinical uses
• The homogeneity of cornea & lens may also
checked,
• Irregularities in the optical structures as black
shadow.
• Small hemorrhages or aneurysms, which can
easily locate.
• Used as distant direct ophthalmoscope.
• Used as BRUCKNER reflex test.
25. Advantages
• Magnification is about 15 x.
• Easier to use with small and undilated pupil.
• Easier mechanically.
• Portable.
26. Disadvantages
• Field of view is smaller
• Peripheral view of retina is not possible.
• It is not easy in viewing the fundus in cloudy
media.
• Stereopsis is not present.
• Limited Illumination.
35. 1. Aperture lever
2. Teaching mirror
3. Convergence
control
4. Filter lever
11. Control for
vertical illumination
A. Press knob
B. Adjuster for over
band
Parts
39. Principle of I.O
The principle of I.O is to
make the eye highly myopic
by placing a strong convex
lens in front of Pt. eye so that
the emergent rays from an
area of the fundus are
brought to focus as a real
inverted image between the
lens & the observer eye,
which is then studied
40. Optical system of I.O
• Binocularity is
achieved by reducing
the observer I.P.D to
approx. 15mm by
prisms/mirror.
41. FIRST ATTEMPT AT BINOCULAR VIEW
Obs. L eye
Obs. R eye
S’s eye
Combine L and R eye views
Observer’s eyes have to be too close
43. IMAGE ORIENTATION
The emergent rays from
the illuminated area of
retina are parallel in
emmetropic Pt. & are
therefore brought to focus
by the condensing lens at
its principal focus, thus an
inverted image of the
retina is formed in the air
between the condensing
lens & the observer.
46. FIELD OF VIEW
20 D
40
Area of binocular view
BINOCULAR FIELD OF VIEW
GTT 04
47. Advantages
• Large field of view.
• Easy to view the extreme periphery.
• Easy to view in cloudy media
• Use of indenter becomes easy.
• Good illumination.
• Hand free for operative purpose.
49. Monocular I O
Its virtue is to permits visualisation of the
fundus through an undilated pupil and the
image seen is errect rather than inverted and
sterioscopic visualisation is not possible.
50. Few difficulties to deal with
• Unwanted reflections of light which comes
from the anterior and posterior surface of the
convex lens and the patients cornea.
• In case of small pupil.
• In case of large pupils.
51. Comparison
Feature Direct Indirect (20 D)
Magnification 15x 3 x
Field diameter 2 DD 9 DD
Illumination Limited High
Depth of focus Small Large
Stereopsis Absent Present
Image
Orientation Upright reversed
Periphery view Limited Full
Working distance Close Arm’s length
Scleral indentation Difficult Easy