The direct ophthalmoscope allows an examiner to perform a preliminary examination of the internal eye including the retina and optic disc. It works by focusing light through a 45 degree mirror into the patient's eye. The reflected light from the retina passes back through the mirror and forms an erect, magnified image that the examiner can view. The size and clarity of the image provides information about the patient's refractive error and can detect conditions like cataracts, retinal detachments, or tumors. By observing how an opacity moves with the patient's eye movements, its location relative to the pupil can be determined.

1. Direct Ophthalmoscope
Dr.Mohammad Khabbaz

2. Methods of Fundus Examination
Direct
ophthalmoscope
indirect
ophthalmoscope
Slit Lamp FFA
B-Scan

3. Direct Ophthalmoscope

6. System of Lens
focusing light on a 45
dgree mirror with
Hole.

7. Mirror reflect light in
diverging beam then
illuminate patient,s eye.

8. Light reflected from
illuminated retina of the
patient ,then passes back
through the hole to
observer,s eye.

9. Image of blub is formed
just below the hole,so the
reflection does not
interfere with viewing.

10. 1.Preliminary examination by a plane mirror at 1
meter    give an idea about refrective error:
 Emmetrope    only red reflex.
 Hypermetropia    with movement.
 Myopia   against movement.
Routine way of using
Direct Ophthalmoscope

11. Red reflex

12. 2.Preliminary examination by a plane mirror at 22 cm
  
 Diagnosis of opacity eg: cataract.
 Recognition of RD or Tumour.
 Level of the opacity can be identified by the
parallactic displacement.
Routine way of using
Direct Ophthalmoscope

14. Movement of the opacity in
relation to the movement of the
observer.
Parallactic displacement

15. Parallactic
displacement
Behind the pupil
opacity moves with
examiner,s motion.
At the pupil
the opacity is stationary
with examiner,s motion.
In front of the pupil
opacity moves opposite to
examiner,s motion.

16. It is method by which an
Erect magnified image
of the fundus can be
seen.
Direct Ophthalmoscope
Definition

18. Macula
disk
vessels

20. • We assume that anterior focal point of the subject (Fs)
coincide with the anterior focal point of the observer
(Fo).
• Image on the examiner,s retina is always inverted   
seen as erect.
Optical principle

21. • Also, the image size varies with the refractive state of
the patient,s eye.
• The image being smaller in hypermetropia,and larger in
myopia than in emmetropia.
Optical principle

26. Emmetropia

27. Rays emerging
from subject,s
retina are parallel

28. Hypermetropia

29. Rays emerging from
subject,s retina are
divergent
Rays enter
observer,s eye
are divergent

30. Inverted
smallest image
Behind the
observer,s retina

31. Inverted
smallest image
Behind the
observer,s retina
The image will
be blurred

32. An emmetropic obsrever has to:
To accommodate or
To use a correcting convex lens
In order to bring the light to
focus in his retina

33. When accommodate
the rays enter his eye
converging so focused
on the retina
The anterior focal
point of the observer,s
eye Fo approaches his
eye

35. Myopia

36. Rays emerging from
subject,s retina are
convergent

37. Inverted
largest image
In front of the
observer,s retina
The image will
be blurred

38. To focus this image on the observer,s
retina he should use a concave lens.

40. The image formed on the observer,s
retina is
• Smaller when a hypermetropic eye is
viewed ,Larger when a myopic eye is
viewed when an emmetropic eye is
examined
• But the use of a correcting lens reduces
the discrepancy in size.

42. The formula for Magnification achieved by a loupe
is
If ascribe dioptric power of 60+ D to the patient,s
emmetropic eye, the magnification of the direct
ophthalmoscope is 15x.
Magnification
Magnification
Dioptric power of the loupe

43. Magnification
 In E----M=60/4=15x.
 In H----M= <15x (F<60D).
 In M----M= >15x (F>60D).

44.  Size of the pupil of subject,s eye.
 Size of the pupil of observer,s eye.
 Error of refraction:
H----> greatest
M----> smallest
 The distance between the observed eye and
observer eye (decrease distance----> increase field)
Ophthalmoscopic
Field of vision