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- 1. Direct & Indirect Ophthalmoscope MahendrdaSingh PhD (Scholar) Assistant Professor and Consultant Optometrist CL Gupta Eye institute, Moradabad UP India
- 2. • Objective methodof 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 bedivided into two types : – Direct ophthalmoscope – Indirect ophthalmoscope
- 4.
- 5. History 1846- Charles Babbage,constructed first ophthalmoscope. 1850’s- Von Helmholtz - Father of ophthalmoscope.
- 6. PRINCIPLE • Work onthe principle of ANGULAR Magnification.
- 7. Optics • A convergentbeam 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 Hyperopicpatient’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 Myopicpatient’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 • Illuminatingsystem 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 • Nervefibre 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 –Focusingsystem • Rack of lenses of different powers in the form of a wheel or chain & accessory filters.
- 15.
- 16. viewing system • Itconsists 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 • Slitdiaphragm - 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 Intermediateaperture Fixation star Slit aperture Filter changing lever Green filter Large aperture Sight hole Blue filter Aperture stop
- 20. Characteristics of imageformed • 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 angularmagnification, 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 seatedin 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 • Thehomogeneity 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 isabout 15 x. • Easier to use with small and undilated pupil. • Easier mechanically. • Portable.
- 26. Disadvantages • Field ofview 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.
- 28. Introduction • Introduced byNagel in 1864 • Very popular method for examination of the posterior segment
- 29. TYPES • BINOCULAR INDIRECTOPHTHALMOSCOPE • MONOCULAR INDIRECT OPHTHALMOSCOPE
- 30.
- 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. Controlfor 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.Locatingpin 16.Slit 17.Fibre optics cable 18.Cord socket
- 38. Accessories used • 1.CondensingLens • 2.Indenter
- 39. Principle of I.O Theprinciple 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 ofI.O • Binocularity is achieved by reducing the observer I.P.D to approx. 15mm by prisms/mirror.
- 41. FIRST ATTEMPT ATBINOCULAR 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 OFVIEW Characteristics of image
- 43. IMAGE ORIENTATION The emergentrays 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 • Arialimage • Real, inverted, magnified
- 45. MAGNIFICATION 20 D lens RI 60 D eye OPHTHALMOSCOPEMAGNIFICATION Peye Plens = 60 D 20 D = 3.0 M =
- 46. FIELD OF VIEW 20D 40 Area of binocular view BINOCULAR FIELD OF VIEW GTT 04
- 47. Advantages • Large fieldof 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 Itsvirtue 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 todeal 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
- 52. Colour Code forFundus Chart
- 53. Color Code forFundus Chart Red Attached retina Arteries Retinal breaks Thin retina Retinal hemorrhages (superficial & deep) Microaneurysms Retinal new vessels (flat & elevated)
- 54. Color Code forFundus Chart Blue Detached retina Retinoschisis Veins Outline of retinal breaks Lattice degeneration BROWN CHOROIDAL DETACHMENT
- 55. Color Code forFundus Chart Yellow Exudates, Drusen Green Media Opacities (label specific lesion) Black Retino-choroidal pigmentation Ora serrata
- 56.