Monocular and binocular IDO

1. SHAHANA
NETHRADHAMA
SCHOOL OF
OPTOMETRY

2. INDIRECT
OPHTHALMOSCOPY
Examination of both the peripheral
fundus and the posterior pole is
possible with indirect
ophthalmoscopy.

3.  Indirect ophthalmoscopy should be used:
• When examining a patient with symptoms of
shadows, hazy vision, flashes of light, and
floaters, which may suggest retinal tear,
detachment or other retinal abnormality.
• When following a patients with systemic
diseases that have retinal manifestations, such
as diabetes, high blood pressure,
cardiovascular disease, sickle cell disease,
infectious and autoimmune diseases.
• In patient with cataract or following cataract
extraction.
• For older patients who are at greater risk of
developing glaucoma and age related macular
degeneration.

4. PRINCIPLE
 Indirect ophthalmoscopy(IDO)involves
making the eye highly myopic by placing
a high power convex lens (+13D to
+30D) infront of the eye so that real,
inverted and laterally reversed image is
formed in front of lens
 The technique is called indirect because
the fundus is seen through condensing
lens.

5.  Two method of indirect ophthalmoscopy:
1. Monocular indirect ophthalmoscopy.
2. Binocular indirect ophthalmoscopy.

6. MONOCULAR IDO
 Monocular IDO is handheld technique
which produces real and erect image.
 It consist of:
 Illumination rheostat at its base
 Focusing lever for image refinement
 Filter dial with red free and yellow filters
 Forehead rest for steady proper observer
head positioning.
 Iris diaphragm lever to adjust illumination
beam diameter.

9. OPTICS
 An internal relay lens system re-invests,
initially inverted image to real, which
then magnified. This image is focusable
using focusing lever.

10. ADVANTAGES:
 Increased working distance from patient
 Increased field of view at low magnification
 Erect, real imaging similar to direct
ophthalmoscopy
DISADVANTAGE:
 Limited illumination
 Fixed magnification
 No stereopsis
INDICATION:
 Need for increased field of view, small pupil,
uncooperative children, patients tolerance of
bright light, basic fundus screening.

11. BINOCULAR IDO
Viewing fundus by allowing stereoscopic
examination.
CHARACTERISTICS :
 Magnification of image depends upon
the dioptric power of convex lens ,
position of the lens in relation of the
eyeball and refractive state of eyeball.
 With a stronger lens image will be
smaller but brighter and field of vision
will be more.

13. PREREQUISITES
i. Indirect ophthalmoscope
ii. Dark room
iii. Convex lens
iv. Pupil of the patient should be dilated.

14. TECHNIQUE:
 The patient’s pupil must be dilated.
 The procedure is explained to the patient and
made to lie in supine position,instructed to
keep both eye open.
 The examiner throw the light into the patient’s
eye from an arm distance with BIO or that
mounted on the spectacle frame.
 Keeping eyes on the reflex the examiner then
interposes the condensing lens(various
power ranging from +15D to +40D) in the
path beam of light close to the patient’s eye
and then slowly move the lens away from the
eye until the image of retina is clearly seen.

16.  The examiner moves around the head of
the patient to examiner different
quadrants of fundus.
 Examiner has to stand opposite to the
clock hour position to be examined
 By asking the patient to look in extreme
gaze and using scleral indenter,
peripheral retina upto ora serrata can be
examined.

18. Field of illumination
 More in myopia and less in
hypermetropia as compared to
emmetropia.

19. Image formation
 Emmetropia
 Myopia
 Hypermetropia

20. EMMETROPIA
 Emmetropic eye, rays from fundus are
parallel, brought to a focus by the
condensing lens.
 Image formed at the principal focus of
lens.
 Hence, size of image remains the same,
no matter the position of lens.

21. MYOPIA
 Rays are convergent
 Image formed in front of the eye
 Final image by condensing lens within
its own focal length
 Image is smaller when lens is nearer to
anterior focus of the eye and larger
when away.

22. HYPERMETROPIA
 Rays are divergent and appear to come
from behind the retina.
 Image by condensing lens in front of its
principle focus
 Image is larger when lens is nearer to
the anterior focus of the eye and smaller
when away

23. Relative position of images
 In emmetropia: at the principal focus
 In myopia: nearer to the lens than its
principal focus
 In hypermetropia: farther away from the
principal focus

24. Factors affecting field of
view
 Patient’s pupil size
 Power of condensing lens
 Refractive error
 Distance the condensing lens held from
the patient’s eye

25. ADVANTAGES
 Wide range of view
 High contrast
 Stereoscopic view
 Variety of lens options
 Excellent depth of focus
 Lesser distortion image

26. DISADVANTAGES
 Inverted and inversed image
 Low magnification
 Dilation required
 Difficult to master