Slit lamp biomicroscopy

all about slit lamp. special features, basic designs, principal of observation system, principal of illumination, animations are done for the beginners for easy understanding,pitfalls.

1. DR.NAFIZ MAHMOOD Slit-lamp biomicroscopy Resident National Institute of Ophthalmology and Hospital B angladesh

2. Why slit lamps are so great gold standard device . This is because they provide… Stereoscopic image V ariable illumination V ariable magnification Excellent image quality

3. WHY NAME SLIT LAMP BIOMICROSCOPE

4. A narrow vertical slit of light is projected on to the eye and permits microscopic examination of living tissues in cross-section

5. History

6. First concept of slit-lamp was introduced by PROF. ALLVAR GULLSTRAND IN 1911 A nd named as LARGE GULLSTRAND OPHTHALMOSCOPE

7. SPECIAL FEATURES The alignment of viewing & illumination system - parfocal long working distance . allows to carry out certain manoeuveres like FB removal from cornea interpose certain optical devices- condensing lens, goniolens , Goldmann applanation tonometer

8. 3 . Incorporated with prisms -invert the image vertically and horizontally -so it appears erect and right way round 4 . A bank of Galilean telescopes of different powers - to allow the magnification

9. What can we use them for?

10. Routine examination of anterior segment Problem-based examination of anterior segment Assessment of anterior chamber depth and angle Contact lens examination Gonioscopy Fundoscopy Ocular photography Contact tonometry ( Goldmann ) Laser photocoagulation On their own With accessories

11. Basic Design

12. Observation system composed of 2 lenses - objective lens - eyepiece lens Objective lens : consists of 2 plano -convex lenses providing a composite power of +22 D

13. Eyepiece lenses : magnification : 10×, 16×, 25× provide good stereopsis as the tubes converged at an angle of 10°- 15 ° Prisms : to overcome inverted image produced by compound microscope

14. OL Fo Fo O Fe Fe i EL I Optics of compound microscope

15. Cross-section of observation system of modern slit-lamp

16. Magnification

17. Slit lamps provide variable magnification Lower magnifications - general assessment and orientation Higher magnifications - detailed inspections of areas of interest There are several ways to do this - Common methods : Littmann -Galilean telescope and zoom systems - Less common methods : Change the eyepieces and/or change the objective lens

18. Littmann -Galilean telescope method A separate optical system is placed in between the eyepiece and the objective Utilizes Galilean telescopes to alter magnifications It consists of a rotating drum that houses Galilean telescopes

19. Galilean telescopes consist of a positive and negative lens that provide magnification based on the lens powers

20. Galilean magnification changer (G) is placed between the slit-lamp objective (O) and the relay lens ( R ) .

21. Illumination system Comprises of : Light source: halogen lamp Condenser lens system Slit and other diaphragms Filters Projection lens Reflecting mirror

22. Mechanical support system Consists of : Joystick arrangement Up and down movement arrangement Patient support arrangement Fixation target Mechanical coupling

23. Technique of biomicroscopy

24. Patient adjustment : should be positioned comfortably in front of slit-lamp with his or her chin resting on the chin rest and forehead opposed to head rest

25. B . Instrument adjustment : - height of the table housing the slit-lamp should be adjusted according to patient’s height - microscope and illumination system should be aligned wth patient’s eye to be examined - fixation target should be placed at required position.

26. C. Beginning slit-lamp examination : some points to be kept in mind Room should be semi-dark Diffuse illumination – used for short time Medications like ointments and anaesthetic eyedrops produces corneal surface disturbance which can be mistaken for pathology. Low magnification should be 1 st used to locate pathology and then higher magnification to examine it.

27. Structures to see through slit-lamp

28. Principal of illumination

29. DIFFUSE ILLUMINATION LIGHT : Full height Broad beam Low brightness DIRECTION : Temporally or Nasally

30. What structures can be seen White light Eye & adnexa

31. Cobalt blue filter with fluorescein Evaluation of fluorescein dye ( appear yellow) staining the ocular surface tissue Tear film To discern the fluorescein pattern in Goldmann Applanation Tonometry [thin marginal tear meniscus and inferior punctate erosions stained with fluorescein ]

32. Red free filter with rose bengal dye Diffuse illumination with red free filter to enhance visibility of rose bengal red dye which has stained keratin in intraepithelial ( squamous ) neoplasia

33. DIRECT FOCAL ILLUMINATION Lamp Microscope The light and the microscope are both pointed at the object of interest

34. Beam : full height medium width medium bright Direction : obliquely Aim : to focus it on cornea so that quadrilateral block ( parallelepiped) illuminates the cornea ANTERIOR SURFACE CROSS-SECTIONAL ILLUMINATION

35. ANTERIOR SURFACE CROSS-SECTIONAL ILLUMINATION POSTERIOR SURFACE

36. Use : 1. to examine the anterior surface & posterior surface of cornea 2. examination of anterior segment & lens 3. for grading of cells & flares ( when the height of the beam is reduced to 2-4 mm)

37. OPTICAL SECTION : when the beam made so narrowed that the anterior & posterior portion becomes very thin leaving only cross sectional illumination of cornea. Optical section: mostly depth

38. Specular reflection i r lamp microscope

39. Beam : medium – narrow ( must be thicker than optical section ) Angle between light & microscope : 50° – 60° Purpose : to observe corneal endothelium . Careful focusing can bring up endothelial cells, like mosaic pattern

40. RETROILLUMINATION Lamp Microscope

41. An object of interest is lit by retro-illumination when the light source is directed onto another structure (deeper) so that the reflected light must pass through that object . Retroillumination of fundus is best performed with - dilated pupil viewing and illuminating arm not parfocal

42. What can be seen Blood vessels of cornea, abnormalities of post. surface of cornea Cataract & PCO iris atrophy

43. Directly illuminated Retro-illuminated Blood vessels of cornea, other abnormalities of post. surface of cornea

44. INDIRECT LATERAL ILLUMINATION DIRECTION : Light is directed just to the side of lesion to be examined Some of the light enters the lesion so it glows internally

45. What can be seen : corneal infiltrates corneal microcyst corneal vacule

46. SCLEROTIC SCATTER BEAM : medium width Direction : on to the limbus - temporally the viewing system focused to center of cornea

47. lamp microscope

48. Sclerotic scatter produces a diffuse glow of limbus and a backlighting of any corneal opacities, as with cornea verticillata ( whorl-like changes) secondary to epithelial deposition of the oral drug amiodarone

49. Pitfalls & pointers Remember to set the oculars to your refractive error or to plano if you are using spectacles. Proper positioning of the patient Intensity of the light at level of patient’s comfort To take advantage of full value of slit-lamp, examiner must become skilled in using all of the methods of illumination and understand when each is best employed.

50. Thank you