Slit lamp techniques.pptx

Slit Lamp, Different Illumination Techniques, Diagnostic and Therapeutic Uses and contact lens fitting

1. SLIT LAMP BIOMICROSCOPY AND DIFFERENT ILLUMINATION TECHNIQUES Raju Kaiti Optometrist Dhulikhel Hospital, Kathmandu University Hospital

2. INTRODUCTION Slit lamp biomicroscope was invented in 1911 AD by Gullstrand. It is named so because it enables the practitioner to observe the living tissues of the eye under magnification in slit and wide view.

3. Introduction An instrument consisting of a high-intensity light source that can be focused to shine as a slit. Used in conjunction with a microscope. The lamp facilitates an examination which looks at anterior segment, or frontal structures, of the human eye, which includes the Eyelid Cornea Sclera Conjunctiva Iris Anterior chamber Natural crystalline lens and Anterior vitreous.

4. Three parts: Illumination system Observation System Physical support Optics Works on the same principle as a Compound Microscope Objective lens(+22.00D) & eye piece(+10.00-+14.00D) Adjustable illumination system

5. The illumination system is in the form of a bright focal source of light with a slit mechanism and circular apertures of various sizes, prism, lamp housing unit, slit width and height control, neutral density filter, cobalt blue light, red-free (green) filter, field size control, diffuser. The observation system is a binocular microscope capable of a wide range of magnification, camera/video adaptor, observation tube, magnification changer. The mechanical support is provided by joystick, headrest and chinrest, screw arrangement for moving instrument up and down, control for slit, width height ,magnification control ,on/off switch and fixation target, locking controls.

6. Observation system Illumination system Mechanical support

7. MAGNIFICATIONS Low magnification: 7X - 10X : General eye Lids. Bulbar conjunctiva/sclera. Cornea/limbus. Tears. Anterior chamber/iris/crystalline lens. Medium magnification: 20X - 25X : Structure of individual layers Epithelium/epithelial breakdown. Stroma. Endothelium. Contact lens fit/lens condition. High magnification: 30X - 40X : Details Epithelium – vacuoles – microcysts – dystrophies. Stroma – striae – folds. Endothelium – Polymegathism – guttata – blebs – cell density.

8. ptmetrist Chinrest Optometrist

9. PRINCIPLE A narrow " 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

10. 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 .

11. How to start? Focus the eye piece Adjust the headrest Position the fixation target Decrease the room illumination Start with diffuse illumination Use appropriate magnification

12. ILLUMINATION TECHNIQUES Diffuse Illumination Direct Illumination Indirect Illumination Retro illumination Specular Reflection Sclerotic Scatter Tangential Illumination Oscillation Technique

13. DIFFUSE ILLUMINATION A diffuse broad beam of light is used and general view of anterior segment of eye is observed 45 degrees angle between light and microscope Open the slit fully Diffusing filter Variable magnification(Low to High)

14. DIFFUSE ILLUMINATION Overall View of: Lids and lashes Conjunctiva Cornea Sclera Iris Pupil

15. DIFFUSE ILLUMINATION Mature cataract Hyphema

16. DIFFUSE ILLUMINATION Giant papillae in a case of VKC Iris tear with lens subluxation secondary to trauma

17. DIRECT ILLUMINATION Observation and Illumination system are focused at the same point Angular separation 40 to 50 degrees between light source and microscope Vary angle of Illumination Low to high magnification Vary width and height of light source Optic section Tall but narrow slit of focused light Less than 0.25 mm wide Parallelepiped section Wider beam of focused light 1 to 2 mm in width Conical Beam Small circular or square spot of light Formed by reducing the height of parallelepiped beam

18. DIRECT ILLUMINATION Optic Section Used primarily to evaluate structural layers of the cornea and lens Estimating the depth of an abnormality such as corneal foreign body or position of cataract Anterior chamber angle- The depth of AC can be observed by Van Herrick's test in which optic section of light is used at corneal limbal area. Localize nerve fibers, blood vessels, infiltrates, and cataracts.

19. Optic Section

20. OPTIC SECTION Corneal FB Corneal opacity Different forms of cataracts Patches of iris atrophy

21. Disc Edema Optic disc coloboma Enlarged Cupping Macular region

22. DIRECT ILLUMINATION Parallepiped Provides a layered view of the cornea and lens Probably the most commonly used Broader view with extensive examination Depth and extent of corneal abrasions, scarring, or foreign bodies

23. Parallelepiped

24. DIRECT ILLUMINATION Conical Beam Most useful technique when examining the transparency of the anterior chamber for the evidence of floating cells and flares, as seen in anterior uveitis Best in darkened room

25. Anterior Chamber cells

26. INDIRECT ILLUMINATION Beam is narrowed to 1 to 2 mm in width The beam is then focused on an area adjacent to the ocular tissue observed and this area is observed in shadow by virtue of scattered light. The foci of the light source and microscope are not coincident

27. INDIRECT ILLUMINATION Angle of illumination can be varied Beam width can be varied Low to high magnification Purpose is to provide somewhat “softer” illumination to give better definition of the structural components of the iris, epithelial corneal edema, pigment spots and corneal foreign bodies Also valuable for observing Epithelial vesicles Epithelial erosions Iris sphincter

28. RETRO ILLUMINATION Formed by reflecting light of the slit beam from a structure more posterior than the structure under observation Purpose is to place the object of regard against a bright background, allowing the object to appear dark or black Search for Keratic precipitates and other debris on corneal endothelium The crystalline lens can be retro illuminated for viewing water clefts and vacuoles of the anterior lens and of posterior subcapsular cataract Corneal edema, neovascularization, microcyst and infiltrates Contact lens deposits

29. RETROILLUMINATION

30. SPECULAR REFLECTION Formed by separating the microscope and slit beam by equal angles from the normal to the cornea i.e. angle of incidence equals angle of reflection Separation for best specular reflection is about 50 degrees Under specular reflection, the anterior corneal surface appears as a white, uniform surface, and the corneal endothelium takes on a golden mosaic pattern Valuable for observing Irregularities, deposits or excavations in the smooth corneal surfaces (will fail to reflect light and thus will appear darker than the surroundings) Changes in endothelium Tear film debris Tear film lipid layer thickness

31. SCLEROTIC SCATTER Formed by focusing a bright but narrow (1mm), slit beam on the limbus and using the microscope on low magnification. This causes the cornea to take on total internal reflection Slit beam should be approximately 40-60 degrees from microscope Halo glow of light around limbus As the light is internally reflected, no light will emerge toward the examiner and so the cornea will appear black An area of reduced light transmission within the cornea however will appear gray Valuable for observing Central corneal epithelial edema Corneal abrasions Corneal nebulae and maculae Foreign bodies in the cornea

32. SCLEROTIC SCATTER

33. TANGENTIAL ILLUMINATION Large angle of 70-80 degrees between illumination and observation system Valuable for observing Iris freckles Tumors General integrity of cornea and iris

34. OSCILLATORY ILLUMINATION the microscope is kept in focus on the structure to be observed and beam is oscillated back and forth alternately resulting in direct and indirect illumination Quick to and fro movement Minutes objects in AC the microscope is kept in focus on the structure to be observed and beam is oscillated back and forth alternately resulting in direct and indirect illumination

35. FILTERED ILLUMINATION Cobalt Blue Red Free filter (green) Neutral Density Valuable for observing Tear layer Ocular staining RGP lens fitting pattern

36. FILTERS Cobalt blue filter is used to locate any lesion in the cornea with the help of fluorescein staining. Also during fitting and trial of RGP lenses. Red free filter i.e. green filter is used to see the vascular pattern of choroid and see any abnormalities in the disc of fundus. Yellow filter is used for general view of anterior segment.

37. Fluorescein and cobalt blue filter

38. Mires in applanation tonometry Fluorescein stain after corneal FB removal Fluorescein pattern in RGP trial Fluorescein pattern in RGP trial

39. Fluorescein and cobalt blue filter

40. CLINICAL USES Diagnostic Anterior segment Evaluation Goldmann Applanation Tonometry TBUT test Staining (Fluorescein, Rose Bengal etc.) Visiometry Gonioscopy FFA and Clinical Photography

41. Therapeutic Epilation Foreign Body Removal Contact lens trial Contact lens fitting characters- static and dynamic Corneal epithelial debridement (herpetic keratitis) Insertion of punctal plugs

42. Corneal Foreign Body Removal

43. Slit lamp techniques in Contact Lens fitting Using the slit lamp, set with a broad beam and low magnification, the practitioner should carry out sweep of the anterior segment and adnexa. Start by examining the lids and lid margins, looking for signs of cysts, styes, meibomian gland dysfunction and other. The cornea is examined next, initially with a medium magnification (x20 to x25), again using a sweep to assess the entire cornea, using a beam width of approximately 2mm (Parallelepiped), initially. Should any anomaly be detected, the magnification can be increased and the beam width also adjusted, accordingly. The cornea should also be assessed after fluorescein installation, prior to any contact lens fitting. Fluorescein stain in conjunction with the cobalt blue light on the slit lamp is used to assess the integrity of the cornea epithelium, which highlights damaged epithelial tissue, in a very reliable and effective manner.

44. Tear film evaluation either tear prism height or TBUT should be assessed using diffuse light. For TBUT cobalt blue filter in conjunction with fluorescein staining is preferred technique. For soft lens trial and RGP lens trial also diffuse illumination is preferred. The static (how the back surface of the lens aligns to the cornea) is well assessed by diffuse illumination but after staining and with cobalt blue filter. Dynamic (how the lens centers and moves on the eye) fitting is also assessed by diffuse illumination Parallelepiped and high magnification- for observation of striae and folds Microcysts seen under high magnification with marginal retro-illumination. Corneal edema, neovascularization, microcyst and infiltrates and Contact lens deposits all are seen through retro- illumination.

45. THANK YOU…………………