Principles of Ophthalmoscopy

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Principles of Ophthalmoscopy

  1. 1. Dr. S. Aswini Kumar. M.D. Professor of Medicine Medical College Hospital Thiruvananthapuram
  2. 2. Hermann von Helmholtz In 1850, invented the ophthalmoscope and revolutionized ophthalmology. Hermann constructed a crude instrument made of cardboard, glue and glass plates from a microscope.
  3. 3. The principle of Ophthalmoscopy: Normally if one shines a beam of light on the pupils, they will constrict, making it impossible to see any portion of the retina from the sides, hence the only way is to look through the light.
  4. 4. The earliest ophthalmoscope: Helmoltz could place his eye in the path of the light rays entering and leaving the patient’s eye, by looking through the source of light, thus allowing the patient’s retina to be seen.
  5. 5. The modern ophthalmoscope: Here light source from the batteries is reflected at 90o using a mirror placed in the head portion at 45o angle. The examiner looks through a hole in the mirror that is through the light.
  6. 6. The structure of an ophthalmoscope: The structure of the ophthalmoscope has remained the same from these nineteenth century ones. They consist of a handle containing a bright light source and a head containing lenses.
  7. 7. The modern ophthalmoscope: The modern ophthalmoscope is compact,efficient as well as durable. It consists of a body and head. The body lodges the batteries and a rheostat for adjusting the intensity of light.
  8. 8. The head of the ophthalmoscope: The head consists of a window for viewing the retina, and one for viewing the lens numbers and a wheel for changing them. Lens numbers are marked in black (positive) & red (negative)
  9. 9. The structure of the head piece: The head portion contains a series of lenses ranging from 1 to 30 diopter which can be selected by turning a side wheel & the red or black coded diopter can be read out through a window
  10. 10. Keep the scope close to the eyes: The ophthalmoscope is brought as close to the eyes as possible, while aligning the apertures of the scope to the pupils so that one can see, in whichever direction he looks.
  11. 11. Asking the patient to look straight ahead: The patient is asked to look at some fixed object at a distance and to keep looking at it. The eyes are not allowed to wander. The patient may blink the eye lids during the procedure.
  12. 12. Approaching the patient’s eye: Keeping the ophthalmoscope close to the examiners eye, the patient is approached with the light from the scope constantly falling on the pupils and apertures brought in a straight line.
  13. 13. All the apertures in a straight line: These apertures are the doctor’s pupil, doctor’s eye window, the lens, patient’s eye window, and the patient’s pupil. Once all the apertures are in a straight line one will see only the retina. Doctor’s pupil Doctor’s Eye Window Patient’s Eye Window Patient’s pupil Lens window
  14. 14. High power lenses for anterior structures: The cornea can be focused and studied clearly using +20 lens. Abnormalities of the cornea like corneal injuries and scars and Keratoconus can be visualized using this technique.
  15. 15. -2 diopter10 diopter 7 diopter14 diopter 0 diopter Choosing the appropriate lens: The structures closer to the ophthalmoscope are best seen using positive lenses, which are labeled with black letters. The retina comes into focus at the 0 diopter, the cup at 2 red.
  16. 16. The Normal Retina: Fundus examination reveals the optic disc in the center and the physiological cup inside it. The vessels are seen emerging from the cup region and diverging out of the disc peripherally
  17. 17. Schematic view of the retina: The retina as seen by ophthalmoscope can have the optic disc, the macula and the fovea. The retinal vessels are seen emerging from the optic disc, the arteries and the veins.
  18. 18. The optic disc and the optic cup: These are seen, a little to the temporal side of the center of the visible retina. The disc has clear margins and a pink color which is lighter than the surrounding retina, the cup is paler.
  19. 19. The physiological cup: is that central portion of the optic disc occupying about 2/3 of its center and slightly depressed than the rest of the disc. Vessels emerge from it. The size & depth are important.
  20. 20. The fovea centralis: It is the slightly more pink area seen about two disc spaces temporal to the disc margin. This is the area which comes into focus when vision is focused and it contains only the cones.
  21. 21. Temporal pallor of the optic disc: The disc is strikingly pale, in a quadrantic or crescentic manner. This is due to involvement of papillomacular bundle. Seen in Multiple sclerosis but not constant or pathognamonic.
  22. 22. Primary Optic Atrophy: The whole disc appears to be white in color, standing out dramatically like a full moon against a dark red sky. The margins of the disc are distinct and the whiteness is uniform.
  23. 23. Papilledema: The area covered by the disc is larger. Margins of the disc cannot be defined. Irregular radial streaks of blood, are seen surrounding the disc. givingnthe disc an angry appearance.
  24. 24. Papillitis or optic neuritis: The degree of swelling is usually slight and the area of the disc is not enlarged and the humping is only mild. It is usually unilateral. The veins are not engorged & hemorrhages absent.
  25. 25. Arteries and veins: The retina as seen by ophthalmoscopy will have the optic disc, the macula and the fovea. The retinal vessels are seen emerging from the optic disc, the veins larger than arteries.
  26. 26. Soft exudates and hard exudates: Soft exudates, otherwise called as cotton wool spots, are fluffy shadows, with indistinct margins, indicating micro-infarcts of neuronal axons. Hard exudates are due to leakage of proteins.
  27. 27. Micro-aneurysms, dot and blot hemorrhages: Micro aneurysms are small rounded pin head size swellings of retinal vessels. On the other hand the dot and blot type of hemorrhages are having irregular shape and fluffy margins. Micro aneurysms Dot hemorrhages Blot hemorrhages Flame hemorrhages
  28. 28. Sub-hyaloid or pre-retinal hemorrhage: They appear as large effusion of blood, related to and often below the disc, with a crescentic inner and clear cut outer margin extending forwards towards the lens. Seen in S. A. H.
  29. 29. Vitreous Hemorrhages: Hemorrhages in the vitreous have more non homogenous appearance with diffuse haziness of the vitreous making it almost impossible to visualize the details of the retina behind.
  30. 30. Central Retinal Vein Occlusion: This gives rise to the picture of extensive blot and dot hemorrhages of the retina, giving it a “blood and thunder” appearance. Disc margins are also swollen and indistinct.
  31. 31. Central Retinal Artery Occlusion: In contrast to the appearance of CRV Occlusion there is extensive pallor of the retina with a very characteristic cherry red spot in the region of the fovea. Disc is normal.
  32. 32. Neovascularization of the disc: When a fresh leash of new vessels are seen anterior to the retinal disc it is called neovascularization. This is secondary to the ischemia of the retina resultant of hypoxemic stimulus.
  33. 33. Retinal detachment: appears as an elevated sheet of retinal tissue with folds. If the fovea is spared the visual acuity is usually normal. If there is a superior detachment there will be an inferior scotoma.
  34. 34. Photocoagulation scars: xThese appear as rounded white opacities, in the periphery of the retina, following retinal laser photocoagulation therapy for proliferative diabetic retinopathy. It usually spares the macula.
  35. 35. Retinal pigmentation: Black deposits of irregular clumps of pigment called as bone spicules are seen especially in the periphery of the retina. Called so because of their resemblance to the cancelous bone

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