Slit Lamp Biomicroscopy.

slit lamp bio microscopy,magnification, uses, advantages

1. Md. Didarul alam 2 nd year B. Optom,ICO,CU Slit lamp B iomicroscopy optometrist

2. Introduction Biomicroscope derives its name from the fact that it enables the clinician to observe the living tissue of eye under magnification . It not only provides magnified view of every part of eye but also allows quantitative measurements and photography of every part for documentation.

3. Important historical landmarks De Wecker 1863 devised a portable ophthalmomicroscope . Albert and Greenough 1891,developed a binocular microscope which provided stereoscopic view. Gullstrand ,1911 introduced the illumination system which had for the first time a slit diapharm in it Therefore Gullstrand is credited with the invention of slit lamp.

4. Large Gullstrand Ophthalmomicroscope (1911)

5. TYPES There are 2 types of slit lamp biomicroscope 1) Zeiss slit lamp biomicroscope 2)Haag streit slit lamp biomicroscope In Zeiss type light source is at the base of the instrument while in Haag streit type it is at the top of the instrument.

6. Zeiss slit lamp biomicroscope Haag streit slit lamp biomicroscope

7. PRINCIPLE A " slit " beam of very bright light produced by lamp . This beam is focused on to the eye which is then viewed under magnification with a microscope

8. Fig:2

9. Topcon slit lamp model SL-3E Light beam is controlled by knobs Joy stick arrangement Chin rest Reflecting mirror biomicroscope Illumination control

10. Magnification may be changed by flipping a lever... Changing filters. biomicroscope Patient positioning Alignment mark Microscope and light source rotate indepedently

11. Instrumentation Operational components of slit lamp biomicroscope essentially consist of: Illumination system Observation system Mechanical system

12. Illumination system It consist of: A bright ,focal source of light with a slit mechanism Provides an illumination of 2*10^5 to 4*10^5 lux . The beam of light can be changed in intensity,height,width,direction or angle and color during the examination with the flick of lever.

13. Condensing lens system: Consist of a couple of planoconvex lenses with their convex surface in apposition. Slit and other diapharm : Height and width of slit can be varied by using knobs. The illumination and observation systems coupled around a common centre of rotation to ensure that the microscope is always focused at the same point as where the slit beam is focused.

14. Observation system(microscope) Observation system is composed of two optical elements 1.an objective ,2.an eyepiece It presents to the observer an enlarged image of a near object. The objective lens consists of two planoconvex lenses facing towards the patient providing a composite power of +22D. Microscope is binocular i.e. it has two eyepieces giving binocular observer a sterescopic view of eye.

15. The eye piece has a lens of + 10D to + 14D towards the examiner. To overcome the problem of inverted image produced by compound microscope ,slit lamp microscope uses a pair of prisms b/w the objective and eyepiece to reinvert the image. Most slit lamp provide a range of magnification from 6x to 40x

16. Mechanical/Physical support A joystick control is employed to enable instrument to be moved left-right/forward-backward (= focus)/ and up-down. A chin rest, head rest and fixation target is also required. Some slit lamps have a tilting mechanism to enable the lamp to be directed from different angles.

17. Used in conjunction with fluorescein stain absorbs blue light and emits green with fluorescein stain. Uses: Ocular staining RGP lenses fitting Tear layer Cobalt blue filter Filters used in slit lamp biomicroscopy

18. Continue…….. Obscure any thing that is red hence the red free light , thus blood vessels or haemorrhages appears black. is used to see the vascular pattern of choroid and see any abnormalities in the disc of fundus . Fleischer ring can also be viewed satisfactorily with the red FREE filter Yellow filter is used for general view of anterior segment. RED FREE FILTER YELLOW FILTER

19. Illumination techniques Diffuse illumination Direct illumination Parallilepiped Optic section Conical(pinpoint) Tangential Specular reflection Indirect illumination Retro-illumination Sclerotic scatter Transillumination

20. Diffuse illumination Angle between microscope and illumination system should be 30-45 degree. Slit width should be widest. Filter to be used is diffusing filter. Magnification: low to medium Illumination: medium to high.

21. Optics of diffuse illumination Diffuse illumination with slit beam and background illumination

22. Applications: General view of anterior of eye: lids,lashes,sclera,cornea ,iris, pupil, Gross pathology and media opacities Contact lens fitting. Assessment of lachrymal reflex.

23. Dirrect illumination Slit beam and microscope are focused on the same area Vary angle of illumination Low to high magnification Vary width and height of light source

24. Optic section Optic section is a very thin beam of light and optically cuts a very thin slice of the cornea. Angle between illuminating and viewing path is 45 degree. Used to localize: Nerve fibers Blood vessels Infiltrates Cataracts AC depth.

25. Optical section of lens 1.Corneal scar with wide beam illumination 2.optical section through scar indicating scar is with in superficial layer of cornea.

26. Parallelepiped : Constructed by narrowing the beam to 1-2mm in width to illuminate a rectangular area of cornea. Microscope is placed directly in front of patients cornea. Light source is approximately 45 degree from straight ahead position.

27. Applications: Used to detect and examine corneal structures and defects. Used to detect corneal striae that develop when corneal edema occurs with hydrogel lens wear and in keratoconus . Higher magnification than that used with wide beam illumination is preferred to evaluate both depth and extent of corneal ,scarring or foreign bodies.

28. Conical beam(pinpoint) Produced by narrowing the vertical height of a parallelepiped to produce a small circular or square spot of light. Light source is 45-60 degree temporally and directed into pupil. Biomicroscope: directly in front of eye. Magnification: high(16-25x) Intensity of light source to heighest setting. Uses Most useful when examining the transparency of anterior chamber for evidence of floating cells and flare seen in anterior uveitis .

29. Indirect illumination Lights enter the eye through a narrow to medium slit (2 to 4 mm) to one side of the area to be examined Illumination narrow to medium slit width decentred slit Magnification approx. M= 12x (depending on object size)

30. Observe valuable for observing Epethelial vessicles Epithelial erisons Irish pathology Irish spincter

31. Schematic of retroillumination from the retina. Example of retroillumination from the retina.

32. Retroillumination

33. Specular reflection Established by separating the microscope and slit beam by equal angles from normal to cornea. Position of illuminator about 30 degree to one side and the microscope 30 degree to otherside . Angle of illuminator to microscope must be equal and opposite. Angle of light should be moved until a very bright reflex obtained from corneal surface which is called zone of specular reflection.

34. Reflection from front surface endothelium

35. Sclerotic scatter It is formed by focusing a bright but narrow slit beam on the limbus and using microscope on low magnification. total internal reflection occurs here The slit beam should be placed approximately 40-60 degree from the microscope. When properly positioned this technique will produce halo glow of light around the limbus as the light is transmitted around the cornea. Corneal changes or abnormalities can be visualized by reflecting the scattered light.

36. Used to observe: Central corneal epithelial edema Epithelial defects Corneal endothelial cell counts Corneal abrasions Corneal nebulae and maculae.

37. Schematic of sclerotic scatter. Example of sclerotic scatter.

38. Tangential illumination Requires that the illumination arm and the viewing arm be separated by 90 degree. Medium –wide beam of moderate height is used. Microscope is pointing straight ahead. Magnification of 10x,16x,or 25x are used.

39. Observe: Anterior and posterior cornea Iris is best viewed without dilation by this method. Anterior lens (especially useful for viewing pseudoexfolation ).

40. Order of Examination Tears Lid margins/Lashes Conjunctiva Cornea Anterior chamber Iris Lens Anterior vitreous

41. Clinical Use Diagnostic Anterior segment Evaluation Goldmann Applanation Tonometry TBUT test Staining ( Flurescein , Rose Bengal etc.) Visiometry Gonioscopy FFA and Clinical Photography Tear evaluation Pachymetry

42. Therapeutic Epilation Foreign Body Removal Contact Lens (fitting and post-wear evaluation) Corneal epithelial debridement (herpetic keratitis) Insertion of punctal plugs

43. References Clinical ophthalmology- jack j kanski Comrephensive ophthalmology- A K Khurana Clinical procedurs in optometry(CPO) Optics & refraction – A K khurana internet

44. Thank you