Indirect Ophthalmoscope.pptx

Ophthalmoscopy

A clinical examination of the posterior segment by the means of an ophthalmoscope.
It is primarily done to assess the state of fundus and detect the opacities of ocular media.

Ophthalmoscope
An instrument that allows the ophthalmologist to look inside a person’s eye and see the details of the living retina

1. INDIRECT OPHTHALMOSCOPY Presenter- Shayri Pillai Liberia Eye Centre JFK Memorial Medical Centre LV Prasad Eye Institute LIBERIA SEPTEMBER 10 2019

2. CONTENTS: OPHTHALMOSCOPY INTRODUCTION HISTORY TYPES PREREQUISITES PROCEDURE

3. SLIT LAMP BIOMICROSCOPY LENS TYPES VOLK DOUBLE ASPHERIC LENS 90 D LEN PROCEDURE

4. INTRODUCTION

5. Ophthalmoscopy A clinical examination of the posterior segment by the means of an ophthalmoscope. It is primarily done to assess the state of fundus and detect the opacities of ocular media. Ophthalmoscope An instrument that allows the ophthalmologist to look inside a person’s eye and see the details of the living retina.

6. TECHNIQUES OF USED FOR FUNDUS EXAMINATION Three methods of examination used in Ophthalmoscopy are: Distant direct ophthalmoscopy Direct ophthalmoscopy Indirect ophthalmoscopy

7. Slit-lamp biomicroscopic examination of the fundus by: Indirect slit-lamp biomiscroscopy Hruby lens biomicroscopy Contact lens biomicroscopy

8. HISTORY 1848- Babbage invented ophthalmoscope 1850- Helmoltz direct ophthalmoscope 1852- Reute 1 st mono ocular indirect ophthalmoscope 1864- Nagel indirect ophthalmoscope 1946- Charles Schepens modern binocular indirect ophthalmoscope

9. TYPES Monocular Indirect Ophthalmoscope

10. OPTICS: An internal relay lens system re inverts the initially inverted image to a real erect one, which is then magnified. This image is focusable using the focusing lever.

11. Parts of Monocular Indirect Ophthalmoscope

12. PARTS: It consists of- Illumination rheostat at its base. Focusing lever for image refinement. Filter dial with red free and yellow filters. Forehead rest for proper observer head positioning. Iris diaphragm lever to adjust the illumination beam diameter.

13. ADVANTAGE : Field of view similar to IO. Erect real image similar to DO. DISADVANTAGE: Lack of stereopsis Limited illumination Fixed magnification.

14. Binocular Indirect Ophthalmoscope

15. INTRODUCTION The binocular indirect ophthalmoscope or indirect ophthalmoscope, is an optical instrument worn on the examiner’s head and sometimes attached to spectacles, that is used to inspect the fundus or back of the eye. It produces an stereoscopic image.

16. Applicable to all refractive errors. Beam penetrates opacities in most media. There is a reduced image size. A wide view of the retina and its defects can be obtained.

17. OPTICAL PRINCIPLE The principle of IO is to make the eye highly myopic by placing a strong convex lens in front of patient’s eye so that the emergent rays from an area of the fundus are brought to focus as a real, inverted image between the lens and the observer’s eye. An aerial image is formed.

18. Fundus image formation Skuta,G.L. et.al. AAO Clinical Optics 2016 Edition.USA chapter 7

19. An aerial image formation Skuta,G.L. et.al. AAO Clinical Optics 2016 Edition.USA chapter-7

20. In the indirect method of ophthalmoscopy a powerful convex lens (called the condensing lens) is held in front of the patient's eye. The usual powers used are +20 D and +13 D. The illuminating light beam passes the condensing lens into the eye and light reflected from the retina is refracted by the condensing lens to form a real image between the condensing lens and the observer. The observer studies this real image of the patient's retina Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-174

21. Image formed by indirect ophthalmoscope Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-174

22. PREREQUISITES: Darkroom Source of light and concave mirror or self illuminated indirect ophthalmoscope. Convex lens (now-a-days commonly employed lens is of +20 D) Pupils of the patient should be dilated.

23. dIAGRAM Parts of Indirect Ophthalmoscope

24. Illumination is usually provided by an electric lamp mounted on the observer's head. Light from this source is rendered convergent by the condensing lens. A convergent beam enters the patient's eye and is brought to a focus within the vitreous by the eye's refractive system. Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-174

25. The light then diverges to strike the retina. The illumination is therefore bright and even, as it comes from the real image of the light source within the patient's eye. Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-174

26. Indirect Ophthalmoscope- Field of Illumination Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-175

27. The condensing lens is held in front of the patient's eye at such a distance that the patient's pupil and the observer's pupil are conjugate foci. Light arising from a point in the subject's pupillary plane is brought to a focus by the condensing lens in the observer's pupillary plane. Conjugacy of pupil Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-175

28. Conjugacy of pupils Skuta,G.L. et.al. AAO Clinical Optics 2016 Edition.USA chapter 7

29. A reduced image of the observer's pupil is formed in the subject's pupillary plane (the image of a 4 mm pupil is approximately 0.7 mm). The observer's pupil is the 'sight-hole' of the system and its size influences the field of view. Construction of the reduced image Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-175

30. The field of view is also limited by the aperture or size of the condensing lens. Only those rays which leave the subject's eye via the image of the observer's pupil and which then pass through the condensing lens will be seen by the observer. Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-175

31. Field view Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-176

32. Light emerging from the patient's eye is refracted by the condensing lens to form a real image of the retina between the condensing lens and the observer. The image is both vertically and laterally inverted (upside down and back to front). It is situated at or near the second principal focus of the condensing lens, i.e. approximately 8 cm in front of a +13 D lens . Elkington A.R.et.al Clinical Optics 3 rd EditionU.K . P-177 PROCEDURE

33. The observer holds the condensing lens at arm's length and thus views the image from a distance of 40–50 cm. To see the image clearly the observer must accommodate or use a presbyopic correction. The binocular indirect opthalmoscopes have +2.0 D lenses incorporated in the binocular prismatic eyepieces so that the observer does not need to accommodate. Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-177

34. Examiner stand opposite the clock hour position to be examined, e.g., to examine inferior quadrant (around 6 O’clock meridian)or the examiner stands towards patient’s head (12 O’clock meridian) and so on. By asking the patient to look in extreme gaze, and using of scleral indenter, the whole peripheral retina up to ora serrata can be examined.

35. Indirect Ophthalmoscopy

36. A retinal indenter will both increase the peripheral view and throw some retinal lesions into relief (for example, retinal tears) so they are more easily seen. The patient is asked initially to look up or down to facilitate placement of the indenter through the lower or upper lid respectively. Indentation

37. The patient then looks towards the indenter and the examiner gently presses on the indenter; a small indentation should be seen in the peripheral retina. The indenter is gently moved round the eye, and again the examiner needs to move around the patient to maximise the view.

38. An indenter

39. Indirect Ophthalmoscope: Linear magnification Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-178

40. Linear Magnification= ab/AB Angle aCF = angle ANB because Ca and AN are parallel Tan aCF = ab/CF =tan ANB =AB/BN Therefore ab/AB = CF/BN CF is the focal length of the condensing lens. BN is the distance between the nodal point and the retina of the subject's eye. Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-178

41. The exact values depend on the distance from which the observer views the real image of the subject's retina, and upon the distance between the condensing lens and the subject's eye if this is ametropic . Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-178

42. The refractive state of the patient's eye affects the size and position of the real image formed by the condensing lens. Indirect ophthalmoscope. Relative positions of the image Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-179

43. All rays emerging from an emmetropic eye are parallel. Rays emerging from a hypermetropic eye are divergent, and the real image is therefore formed outside the second principal focus of the condensing lens. Emergent rays from a myopic eye are convergent, and the real image is therefore always within the second focal length of the lens. Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-178

44. Elkington A.R.et.al Clinical Optics 3 rd Edition U.K. P-174

45. Comparison of view within the same fundus using the indirect ophthalmoscope and the direct ophthalmoscope in DR

46. Biomicroscopic examination of the fundus can be performed after full mydriasis using a slit-lamp and any one of the following lenses: Indirect slit-lamp biomicroscopy- +78 D, +90 D small diameter lenses is presently the most commonly employed technique for biomicroscopic examination of the fundus. Hruby lens biomicroscopy- Hruby lens is a planoconcave lens with dioptric power 58.6D. This lens provides a small field with low magnification and cannot visualize the fundus beyond equator.

47. Contant lens biomicroscopy can be performed by following lenses: Posterior fundus contact lens is a modified Koeppe’lens.The image produced by it is virtual and erect. Goldmann’s three-mirror contact lens consists central contact lens and three mirrors placed in the cone, each with different angles of inclination . With this the central as well as peripheral parts of the fundus can be visualized.

48. A, +78D or +90D, small diameter lens. B, Hruby lens; C, Posterior fundus contact lens (modified Koeppe’s lens); D, Goldmann’s three-mirror contact lens.

49. VOLK DOUBLE ASPHERIC LENSES HISTORY In 1956,aspheric ophthalmic lenses for subnormal vision were developed by Dr. David Volk. He found that an aspheric surface corrected the aberrations present in more common spherical lenses. Several developments ocurred up to 1982 when all Volk lens for indirect ophthalmoscopy were redesigned with both surfaces aspheric, providing substantial improvement in image quality.

50. INTRODUCTION Volk’s 60D,78D and 90d fundus lenses have establishes slit lamp indirect ophthalmoscopy as comprehensive fundus evalution . Examination of the retina by Slit lamp and Volk double aspheric lenses is called a Bio microscopic Indirect Ophthalmoscope BIO.

51. Characteristics Stereoscopic,3 dimensional view of the retina. Binocular viewing through the slit lamp. Better image achieved when viewing through media opacities like cataract. Allows for manipulation of the image. Slit lamp magnification filters. Image size less affected by patient refractive error.

52. Slit-lamp-based indirect lenses 90 D lens Used to carry out indirect ophthalmoscopy using the slit lamp as a light source. Gives more magnification than with a conventional indirect ophthalmoscope, but may not give such ready access to the retinal periphery.

53. It is a useful technique for the examination of the optic disc posterior pole and relatively peripheral retina. An advantage is that examination of the central fundus can also take place with minimal or no dilation of the pupil, although a more accurate examination is always achieved with a dilated pupil. Other commonly used non-contact lenses are variants of the 90 D such as the 60 D, the superfield NC (non-contact) and the 70 D lens.

54. Procedure The slit beam is positioned vertically and centrally in front of the patient’s pupil. The short mirror should be in place. The lens is held in parallel to the patient’s cornea and close to it. The examiner’s fingers can be used to support the eyelids. The slit beam thus passes through the lens and pupil to the retina.

55. The slit lamp is then slowly drawn backwards and towards the examiner whilst the examiner maintains a view through the binocular eyepieces until the inverted retinal image comes into focus. The slit beam is manipulated to vary the area of retina being illuminated and the patient asked to look in the relevant direction to view different areas of the retina.

56. The lens is tilted to look at various parts of the peripheral fundus . Adjustment to the focus also allows the vitreous to be seen. The system of examination is similar to that outlined for the direct ophthalmoscope.

57. Examination with 90 D lens

58. PITFALLS The image obtained at the slit lamp through these lenses is upside down and laterally inverted.

59. Indications Useful method of examination for patients in a general clinic to obtain a view of the fundus, even when the pupil is not dilated. Gives a reasonably magnified image and a good field of view. The optic disc is well seen and the stereoscopic view is useful in analysing the neuroretinal rim. It is also a useful method for delivering laser energy to the fundus, for it does not disturb the corneal surface, giving a clear image.

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