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INDIRECT OPHTHALMOSCOPY ppt
- 1. INDIRECT OPHTHALMOSCOPY Presenter : Dr. A. Soundariya Discussant : Dr. N. Karthika Chair Person : Dr. V. Rajalingam
- 2. History Monocular indirect ophthalmoscope Binocular indirect ophthalmoscope • Optical principle • Parts of indirect ophthalmoscope • Lenses • Technique • Recording the findings • Advantages and disadvantages • Handling the instrument
- 3. HISTORY • Dr. William Cumming • “ every eye could be made luminous if the axis from a source of illumination directed towards a person’s eye and the line of vision of the observer were coincident”
- 4. HISTORY 1850 Hermann von Helmholtz Direct ophthalmoscope 1852 Theodor Reute Monocular indirect ophthalmoscope 1861 Marc Antonie Giracid Tenlon Binocular indirect ophthalmoscope 1946 Charles Louis Schepens Modern binocular indirect ophthalmoscope
- 6. Early binocular indirect ophthalmoscope Charles Schepens
- 7. Early source of illumination
- 8. Modern binocular indirect ophthalmoscope Head mounted Spectacle mounted
- 9. MONOCULAR INDIRECT OPHTHALMOSCOPE Parts of monocular indirect ophthalmoscope
- 10. Indications • Small pupils • Uncooperative children • Basic fundus screening • Intolerance to bright light
- 11. Advantages • Increased field of view • Erect real image Disadvantages • Lack of stereopsis • Limited illumination • Fixed magnification • Fair to good resolution
- 12. BINOCULAR INDIRECT OPHTHALMOSCOPE • Principle • The principle of indirect ophthalmoscope is to make the eye highly myopic by placing a strong convex lens in front of the patient's eye • When both the illuminating and reflecting beam pass through the pupil, that area of fundus is seen.
- 14. ILLUMINATION
- 15. ILLUMINATION
- 16. ILLUMINATION
- 17. ILLUMINATION
- 18. ILLUMINATION
- 19. IMAGE FORMATION
- 20. IMAGE FORMATION
- 21. IMAGE FORMATION
- 22. IMAGE FORMATION
- 23. IMAGE FORMATION
- 24. IMAGE FORMATION
- 25. IMAGE FORMATION
- 26. IMAGE FORMATION
- 27. IMAGE FORMATION
- 28. IMAGE FORMATION
- 29. STEREOPSIS
- 30. STEREOPSIS
- 31. GULLSTRAND’S PRINCIPLE • Reflex free ophthalmoscope
- 32. GULLSTRAND’S PRINCIPLE • Reflex free ophthalmoscope
- 33. BRIGHTER ILLUMINATION • Bright and even • Hazy media
- 34. FIELD OF ILLUMINATION • Depends on pupil size • Varies with refractive status of patients eye
- 35. FIELD OF VIEW Determined by • Observer’s pupil size • Aperture of the condensing lens
- 36. FIELD OF VIEW • 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.
- 37. FIELD OF VIEW • A reduced image of the observer’s pupil is therefore formed in the subject’s pupillary plane.
- 38. FIELD OF VIEW • Only those rays of light which leave the subject’s eye via the area of image of the observer’s pupil can, after refraction by condensing lens, enter the observer’s pupil and be seen by him.
- 39. FIELD OF VIEW • Field of view also limited by the aperture or size of the condensing lens
- 40. FIELD OF VIEW Determined by • Observer’s pupil size • Aperture of the condensing lens
- 41. MAGNIFICATION Factors affecting magnification • Power of the condensing lens • Viewing distance • Patient’s refractive error
- 42. PARTS OF BINOCULAR INDIRECT OPHTHALMOSCOPE
- 43. Filters • Yellow filter – reduces intensity of light • Red free filter – blood, membranes, new vessels and retinal nerve fibre layer defects • Blue filter – flourescein angiography
- 44. INDIRECT OPHTHALMOSCOPE LENSES Biconvex aspheric lenses with one surface more curved than the other. Functions • Acts as a condensing lens for the light coming from illumination system • Acts as a lens for forming an inverted , laterally reversed, real aerial image of retina
- 45. • The technique is called indirect because the fundus is seen through a condensing lens • The image is formed close to the principle focus of the lens, between the lens and the observer • The power of the condensing lens determines Retinal magnification Field of view Stereopsis
- 46. Power of lens ( D ) Magnification Field of view + 14 D 3.5 X 35 degree + 20 D 2.5 X 45 degree + 28D 1.5 X 55 degree
- 48. Uses • 30 D - To obtain panoramic view when detail and stereopsis are not important and used with small pupil • 20 D - most widely used as it provides an adequate field of view, stereopsis and magnification • 14 D – useful for detailed view of macula and optic disc; for determining elevation of retina in shallow retinal detachment
- 49. TECHNIQUE OF INDIRECT OPHTHALMOSCOPY Pupil dilation • Tropicamide 1 % and • Phenylephrine 2.5 %
- 50. Adjusting the IDO headset • Adjust the head band • Adjust the IPD • Set the light aperture • Light filter • Adjust the light intensity
- 51. Parts of IDO IPD Adjustment
- 52. Positioning the patient • Patient should lie flat in a reclining chair • Space to move freely around the head
- 53. Choosing the right lens • Lenses available are + 14D, + 20D , + 28D, +30D • +20D lens is commonly used
- 54. Minimising lens distortion • Because of the aspheric nature of lens, we should hold the lens right side up , to minimise distortions
- 55. Examining the patient • Explain the procedure to the patient • Dark room • Make the patient lie supine • Instruct to keep both eyes open • Illuminate the patients pupil area by pointing the illumination towards patient’s eye
- 56. • Interpose the condensing lens in the path of beam of light • Slowly move the lens away from the eye until a clear image of retina is seen • Examine the fundus by moving around the patient • Examiner should stand opposite the clock hour position to be examined
- 57. Proprioception helps to look in different gazes Holding the lens
- 59. Scleral indentation • Trantas • Thimble depressor- Schepens • Hand held scleral depressor
- 60. Technique of holding the depressor
- 62. RECORDING THE FINDINGS Amsler Dubois chart Positioning of chart for drawing
- 63. FUNDUS DIAGRAM
- 64. ADVANTAGES OF INDIRECT OPHTHALMOSCOPE • Larger field of view • Lesser distortion of retinal image • Stereoscopic view • Useful in hazy media • Can visualize retina anterior to equator • Vitreous can be examined • Can be used intraoperatively
- 65. DISADVANTAGES OF INDIRECT OPHTHALMOSCOPE • High learning curve • Less magnification • Difficulty with very small pupils • More uncomfortable to the patient • Confusing reversed image
- 66. HANDLING • Wipe the headband and instrument surfaces with a cloth dampened in mild disinfectant every day • Clean the lens by using hard contact lens cleaner and warm water , then dry it with a soft lint - free cloth • Sterilise the condensing lens – placing in a cidex solution for 5 – 10 minutes; can also autoclave the lens in a steel chamber with perforation for steam
- 67. • Handle the knobs gently • Start with minimum light • Rest when the bulb is hot • Wire discipline • Recharge the batteries at end of each work day • Keep the instrument in its case when not in use
Editor's Notes
- A front runner in field of ophthalmology 1846
- 1851 helmhotz published the optical principles involved Reute – concave mirror with aperture Tenlon – france Earliest source of illumination candle; later lamps incorporated a reflecting mirror behind the candle and a strong convex lens in front to condense the light Reflex free ophthalmoscopy Thornerand Allvor Gullstrand 1911
- Intro by reute, it was designed for its use in undilated pupil, Original monocular io used an external light source reflected by a mirror held in front of observer’s eye The monocular indir method allows use of low power lenses (13d) thru which small details are seen larger Since it is monocular stereoscopic exmn not possible
- The emergent rays from an area of fundus are brought to focus as a real inverted image between the lens and observer’s eye
- Assuming the ptnt eye is emmetropic Parallel ray of light 20 D LENS covex lens Img is formed 5 cm in front of condensing lens
- Assuming the ptnt eye is emmetropic Parallel ray of light 20 D LENS covex lens Img is formed 5 cm in front of condensing lens Img is magnified but not as mag as in DO Img is real, inverted, laterally reversed
- Emmetropic eye : parallel rays – converge by condensing lens - img fomed in focal plane Myopic eye : emergent rays are converging- further converged by the condensing lens- img formed much closer to the convex lens Hypermetropic eye : emergent rays are diverging- converged by condensing- but img formed beyond the focal plane i.e, farthet from the condensing lens IMAGE FORMATION VARIES WITH REFRACTIVE STATUS
- NOW HOW TO VISULAISE THE IMG All we need to do is accomodation- we can see the img clearer If we ( observer ) unable to accommodate, we can use our presbyopic correction glasses/ contact lens IO has incorporated some power in ocular which we can use to focus At 1/3 rd meter : 3D accomodation needed Change of +/- 0.1D in observer’s accomodn accounts for +/- 5D in ptnt’s refrac error Thus, minor changes in examiners accomodation can easily compensate for major refractive error that ptnt may have
- For stereoscopic view, we should see with both eye, and also we should adjust the IPD so that both viewing beam fits into the patients pupil Normal IPD is 60 mm, reduced to 15mm by use of prism IDO
- Normal IPD is 60 mm, reduced to 15mm by use of prism IDO
- Presence of corneal reflection and usual backscattering of light from healthy cornea and lens make the evaluation difficut Gullstrand evaluated the principle . Observation and illumination beam be separated at corneal and lens plane to avoid reflection and scattering for which a DILATED PUPIL IS needed With ptnt and observer pupil conjugate , loss of light is minimized and field of view is maximised
- The illuminating beam and viewing beams must be totally separated through cornea , pupillary aperture and lens to avoid reflection, but must coincide on retina to permit viewing
- ILLUMINATION is provided by an electric lamp mounted on observers head. Light from this source is rendered convergent by the condensing lens. Thus a convergent beam enters the ptnt’s eye and is brought to a focus within the vitreous by eye’s refractive system. The light then diverges to strike the retina. The illumination is therefore bright and even, as it comes from the real mage of the light source within the ptnt’s eye.
- Largest in myopia , smallest in hypermetropia In all refractive states, size of subject’s pupil limits the field of illumination
- It is usual to dilate the ptnt’s pupil widely prior to IDO exmn , in order to increase the fied of illumination. It is not practical to dilate the observer’s pupil bcus his VA wud be impaired. This is bcus he wud suffer an increase in aberrations and l/o accomodan, the latter being particularly troublesome for low hypermetrope. Therefore a condensing lens of largest possible aperture is chosen to inc the field of view. THE lens redirects the peripheral rays towards the obsever’s eye
- This means that light arising from a point in subject’s pupillary plane is brought to focus by the conden lens in observer’s pupillary plane and vice versa
- - Image of a 4mm pupil is approx 0.7 mm
- Only those rays which leave the subjects eye via the image of observer pupil and which passes through the condensing lens will be seen by the observer. Therefore , field of view is determined by the observer’s pupil size and the aperture of the condensing lens
- It is usual to dilate the ptnt’s pupil widely prior to IDO exmn , in order to increase the fied of illumination. It is not practical to dilate the observer’s pupil bcus his VA wud be impaired. This is bcus he wud suffer an increase in aberrations and l/o accomodan, the latter being particularly troublesome for low hypermetrope. Therefore a condensing lens of largest possible aperture is chosen to inc the field of view. THE lens redirects the peripheral rays towards the obsever’s eye
- 1) Magnification is a function of power of the condensing lens to power of the patient’s eye. Eg: emmetropic eye (60 D) , with condensing lens of 20D= 60/20= 3X magnification In a 10 D MYOPE , 70/20 = 3.5X magnification 2) The reference point for designation of magnification is 25cm; if the image is viewed from more than 25cm, the perceived magnification decreases proportionately 3) In myopia , img size increases as the conden lens is moved towards ptnt’s eye, while in hypermetropia the img size inc if lens is moved away from ptnt’s eye
- Light sources : halogen light, LED ( much cooler and last longer) Battery – in examiners belt or incorpor in headband itself
- Yellow- offers protection to the user because of decreased inten of light entering the ptnts eye and may even offer protectn to ptnts retina or provide comfort to the patient -Red – subtle pigmentary changes
- Aspheric lenses – peripheral distortions reduced
- Condensing lens is a powerful convex lens
- Working dist from cornea 72mm, 47mm & 26mm respectively Stereopsis 1, ¾, ½ Mag= power of eye/power of lens; field= power of lens * 2; stereopsis= mag/4 30D lens has highest magnif DO 15X 12.5 deg 2.5 DD DD 5, 8.5,11
- 28D viewing pathology near ors serrata is easier with 28D. It has magnificn of around 2.2 times but offers a larger dynamic field of view of 69 degree
- Nowadays lenses are coming with antireflective coating i.e yellow filter within , to reduce blue light ( blue light causes scaterring and glare )
- To conduct a good peripheral exmn, the ptnts eye must b well dilated. Use both tropicamide and phenylephrine. Ptns with dark colored iris may need more than one set.
- So that scope is secure on your head and height of the beam so you can see a full beam with each eye Set light aperture to the largest spot for a fully dilated pupil, use the smallest aperture for small pupils and intraocular gas Filter – generally we use white light filter. A diffuser can improve the field of view and is softer and more comfortable to the ptnt to allow yourself a clear view while attempting to make the ptnt comfortable
- 20 D double aspheric lens has magnificn upto 3 times. Used to evaluate macula and periphery. Dynamic field of view is 60 degree 28D viewing pathology near ors serrata is easier with 28D. It has magnificn of around 2.2 times but offers a larger dynamic field of view of 69 degree
- The silver line should be towards the patient , so that the surface with steeper curvature is towards the examiner- to decrease the aberrations Move the lens in and out to focus and refine the view Aspheric – means two different curved surfaces to avoid spherical abertn
- Start with lower illumin and slowly incr the illum
- Proprioception helps ptnt to look in diff gazes Rest the frree fingers on ptnts cheek or forehead Less convex side towards patnt Gently tilt the lens to avoid disturbing reflexes Held at 5cm from ptnt Distance from the eye = focal length of the lens
- Eg: to examine the inf quadrant, we shld stand at head end i.e at 12 o clock and ask the ptnt to look DOWN By asking the ptnt to look in extreme gaze and by using the scleral indenter the whole periphery upto ora can be examined
- Schocket scleral depressor, Cotton tip applicator Done with dep placed over lid This helps in making the barely perceptible lesions more prominent, can better appreciate the dif ts color and densities Most sensi part is superonasal quadrant
- Should move the dep in a direction opp to that in which examiner wishes to the dep to appear Scl dep shld be rolled gently and tangentially over the surf
- Img seen in ido is inverted and laterally reversed The chart is placed upside down i.e 12 o clock of chart placed towards feet so that the img fields can be visually translated directly onto the paper without having to mentally invert them
- 1) 10 fold increase in area of retina visible as compared to dir ophthalmoscope 2) 3)With considerable depth perception 4) Bcus of its bright light and optical ppty. As IDO is a larger instrument there is more scope for fitting more powerful light sources 5) Where most retinal holes and degenerations exist 6) Various vitreous abn can be diagnosed 7) Bcus it is used at a distance whch slows to preserve a sterile operative field Laser energy can be delivered thro the ido to effect retinal photocoagln
- 1) 2) In comparison with DO 3) 4) Due to intense light and scleral indentation 5 expensive
- Make sure the instru is switched off before is kept in case