Direct & Indirect Ophthalmoloscope.pdf

Direct and Indirect ophthalmoscope

1. Direct & Indirect
Ophthalmoscope
MahendrdaSingh
PhD (Scholar)
Assistant Professor and Consultant Optometrist
CL Gupta Eye institute, Moradabad UP India

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

4. Direct
Ophthalmoscope

5. History
1846-Charles Babbage, constructed
first ophthalmoscope.
1850’s-Von Helmholtz -Father of
ophthalmoscope.

6. PRINCIPLE
•Work on the principle of ANGULAR
Magnification.

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

10. Instrumentation
•Illuminating system
•viewing system

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.

14. viewing system
–Sight hole
–Focusing system
•Rack of lenses of different powers in the form
of a wheel or chain & accessory filters.

15. Lens track
chain
Eyebrow rest
Sight hole

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

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

21. Magnification
Depend on angular magnification,
Therefore A M is achieved by
AM=POWER OF THE EYE/4
M=60/4
=15X.

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.

27. Indirect
Ophthalmoscope

28. Introduction
•Introduced by Nagel in 1864
•Very popular method for examination of the
posterior segment

29. TYPES
•BINOCULAR INDIRECT OPHTHALMOSCOPE
•MONOCULAR INDIRECT OPHTHALMOSCOPE

30. Indirect Ophthalmoscope

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

36. Parts
5. Unscrew
knob
6. Control for
over band
7.Circumferen
ce adjuster
8.Height
adjuster
9.Over band
10.optics.

37. Parts
12.Brightness selection
13.Bulb connector
14.Bulb
15.Locating pin
16.Slit
17.Fibre optics cable
18.Cord socket

38. Accessories used
•1.Condensing Lens
•2.Indenter

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

42. IMAGE ORIENTATION
MAGNIFICATION
FIELD OF VIEW
Characteristics of image

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.

44. Image formed
•Arial image
•Real, inverted, magnified

45. MAGNIFICATION
20 D
lens
RI
60 D
eye
OPHTHALMOSCOPE MAGNIFICATION
P
eye
P
lens
=
60 D
20 D
= 3.0M =

46. FIELD OF VIEW20 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.

48. Disadvantages
•Low magnification.
•It cannot be well perform in undilated pupil.
•Mechanically not easy.
•Not portable.

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 DirectIndirect (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 DifficultEasy

52. Colour Code for Fundus Chart

53. Color Code for Fundus Chart
Red
Attached retina
Arteries
Retinal breaks
Thin retina
Retinal hemorrhages (superficial
& deep)
Microaneurysms
Retinal new vessels (flat &
elevated)

54. Color Code for Fundus Chart
Blue
Detached retina
Retinoschisis
Veins
Outline of retinal breaks
Lattice degeneration
BROWN
CHOROIDAL DETACHMENT

55. Color Code for Fundus Chart
Yellow
Exudates, Drusen
Green
Media Opacities
(label specific lesion)
Black
Retino-choroidal pigmentation
Ora serrata

56. •Thank you