Slit lamp

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Slit lamp

  1. 1. Slit lamp <br />By <br />praveen.p<br />D.optom,B.optm<br />
  2. 2. Slit lamp are used in the examination of the anterior segment of the eye .<br />Where they allow the practitioner to perform a careful examination of cornea ,conjunctiva and lids.<br />In modern instrument the microscope and light source are coupled so that the light shines on the same part of the eye that the microscope is focused .<br />
  3. 3. This coupling facilitates examination of the eye .<br />The instrument is called a slit lamp because in the normal mode of operation .<br />The light source produces a thin vertical slit of light at the eye .<br />When this slit of light shines along a different axis to that of the microscope the clinician see a section of living eye.<br />
  4. 4. Main parts of slit lamp<br />Silt lamp microscopes<br />Illumination systems .<br />Mechanical coupling .<br />
  5. 5.
  6. 6. Attachments of slit lamp<br />Fundus examination <br />Gonioscopy<br />Tonometry<br />Laser photo coagulation <br />Measuring the visual acuity in patients with hazy media .<br />
  7. 7. Slit lamp microscopes<br />The magnification of slit lamp microscope is usually with in the range of *6 to * 40 .<br />At higher magnifications the small and often uncontrollable movement of the patient’s eye make the image jump around so much that an examination cannot be performed satisfactorily .<br />This range of magnifications and the large working distance mean that compound rather than simple microscope have to be used .<br />
  8. 8. In most basic form composed of microscopes are composed of two optical elements .<br />An objective and an eyepiece .[in the fig shown as two simple positive lenses.<br />In reality the eye piece and occasionally the objective are composed of a series of lenses to reduce aberrations .<br />
  9. 9. Range of magnifications<br />The use of different objectives.<br />The use of different eyepieces. <br />The Littmann- Galilean telescope principle .<br />With a zoom system .<br />
  10. 10. The use of different objectives<br />This is one of the oldest and possibly still the most frequently used technique for obtaining different magnifications .<br />The different objectives are usually placed on a turret type of arrangement that allows them to be fairy rapidly changed during an examination .<br />
  11. 11. The system is usually limited to two sets of objective lenses due to the confinements of space in and around the objective area of slit-lamp.<br />
  12. 12. The use of different eye pieces <br />This technique is usually used in the cheaper slit lamps it is the only means of changing the magnification .<br />It is not a very convenient technique as it requires the practitioner to pull out the current eye pieces and replace them<br />Normally they are kept in a drawer attached to the instrument table .<br />
  13. 13. More than two pairs of eye pieces to be provide with the slit lamp .<br />The technique alone provides a very limited range of magnifications.<br />
  14. 14. The littmann Galilean telescope principle<br />The Galilean magnification changer developed by littmann [1950] <br />It is completely separate optics that sit nearly bw the objective and eye piece lenses and does not require either of them to change .<br />It provides a larger range of magnifications than the other technique .<br />
  15. 15. Typically five via a turrent arrangement which is completely enclosed within the microscope’s body .<br />It is called Galilean system because it utilizes Galilean telescopes to alter the magnification .<br />The Galilean telescopes have two optical components a positive and a negative lens . <br />
  16. 16. The parallel light rays both enters and leaves the system and under goes some degree of magnification which is dependent upon the power and separation of two lens .<br />Galilean telescope fits with in the standard slit lamp microscope along with a rely lens in the manner .<br />By reversing the order of the lenses in the telescope a different magnification can be achieve with out altering any optical elements.<br />
  17. 17. Zoom systems<br />Recently expensive slit-lamps have been produced with a zoom systems that allow a continuously variable degree of magnification .<br />The Nikon instrument contains the zoom system with in the objective of the microscope and offers a range of magnifications from *7 to *35.<br />
  18. 18. Illumination systems<br />The objective of the slit-lamp illumination system is to produce a bright light evenly illuminated ,finely focused ,adjustable slit of light at the eye .<br />Almost all slit –lamp manufactures have adopted the koller illumination system .<br />
  19. 19. Koller illumination system <br />The filament of the bulb is imaged by the condenser lenses at or close to projector lens .<br />The projector lens forms an image of the slit at the eye .<br />The diameter of the projection lens is usually fairly small in size.<br />This has two advantage :- first is keep the aberrations of the lens down ,which results in a better quality image .<br />
  20. 20. Second :- it increases the depth of focus of the slit and thereby produces a better optical section of the eye .<br />While the optics of the condenser are not as critical as that of the other elements of the slit – lamp care must be taken in their design so as not to introduce too much chromatic aberration which will tend to cause fingers at the slit image .<br />
  21. 21. To reduce the aberration is normally achieved by using two or more lenses in the condenser system .<br />The light source used in slit –lamp illumination systems is a tungsten filament bulb .<br />For safety reasons ,they are run on relatively low voltages <br />Slit-lamp can now be obtained with halogen filled bulbs. <br />
  22. 22.
  23. 23. The diag slit-lamp <br />It use a optic fiber to convey the light from a high –power halogen bulb .<br />It is housed in a special fan cooled box to the slit lamp . <br />
  24. 24. Advantage <br />Decrease the weight of slit- lamp <br />Allow it to be hand held by the practitioner . <br />
  25. 25. Mechanical coupling of microscope and illumination system <br />Microscope and illumination system slit-lamp are linked together around a common axis or rotation that co insides with their focal plans.<br />Microscope focused where the illumination system is focused .<br />Without changing the focus the microscope and the illumination system can rotated around their axis .<br />
  26. 26. The movement towards or away from the eye and from side to side is usually achieved via a joy stick .<br />Up and down movement is obtained via some screw device .<br />
  27. 27. Optom.praveenmails @gmail.com<br /> Relax<br />
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