SLIT LAMP AND ITS DIFFERENT ILLUMINATION TECHNIQUES.pptx

This presentation explains in detail about different illumination techniques and filters used in slit lamp examination and the procedure to perform slit lamp examination.

1. SLIT LAMP AND ITS DIFFERENT ILLUMINATION TECHNIQUES Presented by- Abhishek Kashyap B.Optom 3 rd year Ridley College Of Optometry

2. Layouts Introduction History Designs Parts Different Illumination technique Procedure References

3. Introduction The slit lamp is a microscope designed specifically to examine the eye It is used to examine the external ocular adnexa, external eye, anterior chamber, iris, crystalline lens, and the anterior face of vitreous

4. The term “Slit Lamp Biomicroscopy” was coined because of slit beam emitted by the illumination system and the microscope use to examine the living eye

5. History Purkinje (1823), attempted to develop a type of slit lamp by using one hand-held lamp to magnify an another hand-held lens to focus strong oblique illumination De Wecker (1863), devised a portable ophthalmomicroscope that combined a small monocular microscope which rest against the face of the patient with an attached condenser lens. It lacked stereoscopic view

6. Albert and Greenough (1891), developed a binocular microscope which provided stereoscopic view Czapski (1897), modified the binocular corneal microscope, which is still found in many modern slit lamps Gullstrand (1911), introduced the illumination system which had for the first time a slit diaphragm in it

7. Henker (1916), developed the prototype of the modern biomicroscopy by combining the Gullstrand’s slit-illumination system with the Czapski’s binocular corneal microscope Hans Goldmann (1933), improvised the biomicroscope in which all the vertical and horizontal adjustments for both the lamp and the slit beam were placed on a single mechanical stage. The slit-lamp designed by Goldman was marketed in 1937 as the Haag- Streit model 360 slit lamp

8. Littmann (1950), incorporated the rotatory magnification changer based on the principle of Galileon telescope. The slit lamp designed by Littmann is the forerunner of the current Zeiss slit-lamp series

9. Designs of biomicroscopes Zeiss Biomicroscope Haag- Streit Biomicroscope

10. Parts of slit lamp

11. The slit lamp biomicroscope is composed of following parts: 1) Mechanical support  forehead rest  chin rest  fixation target  power supply unit  joystick arrangement

12. 2) Observation system:  objective lens  eyepiece  prism  magnification changer

13. 3) Illumination system  lamp house unit  condenser lens system  slit width and height control  filters  projection lens  mirror or prism

14. Figure : Optics of Slit lamp

15. Illumination techniques Diffuse illumination Direct illumination Indirect illumination Retro-illumination Specular reflection Sclerotic scatter Tangential

16. Diffuse illumination Set up: - angle between microscope and illumination system should be 30- 45 ̊ - slit width should be widest - diffusing filter - magnification: low to medium - illumination: medium to high

17. Used for: - General view of the anterior eye - contact lens fitting

18. Direct illumination Observation and illumination systems are focused at the same point Angle : 30- 60 ̊ Magnification : low to high Variation in the width and height of the light source will give the following: - optic section - parallelopiped - conical beam

19. Optic section It is produced by a very narrow slit beam focused obliquely Used for: - observation of variation in corneal curvature - variation in corneal thickness - depth of the corneal pathologies - cataract - anterior one-third of the vitreous

20. Anterior chamber angle grading by Van Herrick method can be done by the use of optical sections An angle of 60 ̊ is set between illumination and observation systems A very narrow slit of 1mm width and 3 mm height is directed towards the limbus at 3 or 9 o’ clock, normal (90 ̊ ) to the surface at the limbus

21. The anterior chamber depth is compared with the corneal thickness Chamber depth less than or equal to a quarter of the corneal thickness are of concern

22. Grading according to Van Herrick

23. Parallelopiped The illumination is same as optic section except that the beam is broader than optic section The width of the beam is 2-3 mm Used for: - observation of pathologies of epithelium and stroma - corneal scars or infiltrates (appears brighter) - striae and folds

24. Conical beam It is a small circular beam use to examine the presence of cells and flare Set up:  the room should be dark  beam - small circular pattern  light source – 45-60 ̊ temporally and directed into the pupil  magnification – medium to high

25.  focusing – beam is focused between the cornea and the anterior lens surface, and the dark zone between cornea and lens is observed

26. Indirect illumination Observation and illumination systems are not focused at the same point Focal light beam is directed adjacent to the area of observation Set up:  angle : 30-45 ̊  beam width used is moderate  illumination : low – high

27. Valuable for observing: - corneal infiltrates - corneal microcysts - corneal vacuoles - epithelial cells - iris pathology

28. Retroillumination Object of interest is illuminated by light reflected from the structures behind it Two types-  Direct : see the cornea just infront of the illuminated area  Indirect : see the corneal area adjacent to the illuminated area

29. Direct retroillumination Indirect retroillumination

30. Set up: - create a parallelopiped - illuminate the area behind the corneal area to be seen - magnification medium to high - observe the cornea in the reflected light

31. Valuable for observing: - contact lens deposits - crystalline lens opacities - epithelium oedema - microcysts - vacuoles - dystrophies - neovascularization

32. Specular reflection Angle of incident light is equal to the angle of reflected light Set up :  the angle between the microscope and slit beam is about 60 ̊  create a parallelopiped beam  high magnification and illumination is use

33. Valuable for observing: - endothelial cells - tear layer stability and lipid layer - contact lens surface wetting

34. Sclerotic scatter Illumination of the cornea is done by total internal reflection The light beam is directed at the limbal region while observing the cornea Utilizes a parallelopiped technique Magnification of 6-10x is used

35. Valuable for observing: - corneal opacity - corneal scar - foreign bodies in the cornea

36. Tangential illumination Large angle of 70-80 ̊ is created between the illumination and observation system Observation system is directed in front of the eye being examined and illumination system is directed obliquely Valuable for observing: - iris freckles - tumours - general integrity of the cornea and iris

37. Filtered illumination

38. Routine examination of the eye

39. Procedure Ensure that the slit lamp is plugged in Clean forehead and chin rest Bring the table into position in front of the patient Adjust the chin height to position eyes at the level of the black indicator line with head in contact with the forehead band The patient can be instructed to hold the handlebars

40. 6. Set oculars at ‘0’ and adjust interpupillary distance like binoculars 7. Unlock the carriage 8. Adjust coarse focus by moving the entire carriage forward and backward at the base 9. Move the joystick into position: turn clockwise to raise, counterclockwise to lower 10. Turn the power switch on

41. 11. Adjust beam width and intensity 12. Set the light on the correct filter 13. Adjust the height of the beam 14. Move the beam angle by swiveling the illumination while hold ing the beam width knob 15. At the conclusion of the exam lock the carriage in place 16. Turn off the slit lamp power switch

42. References Theory and practice of optics and refraction, 3 rd edition, by A K Khurana, Page No 351-361 Primary care optometry, 4 th edition, by Theodore Grosvenor, Page No167-176 The IACLE module 1, 1 st edition, Page No189-235 The slit lamp primer, by Janice K. Ledford and Valerie N. Sanders, Page No2-85 https://eyewiki.aao.org/Slit_Lamp_Examination