Slit Lamp Biomicroscopy


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Slit Lamp Biomicroscopy

  1. 1. MANOJ ARYAL B . Optometry IOM,MMC Slit lamp Biomicroscopy (Instrumentation,Principle, Illumination and Uses) optometris t
  2. 2. Introduction  Biomicroscope derives its name from the fact that it enables the practitioner 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. 3. • 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 –Aqueous –Natural crystalline lens and –Anterior vitreous.
  4. 4. 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.
  5. 5. Large Gullstrand Ophthalmomicroscop e (1911)
  6. 6. 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.
  7. 7. Zeiss slit lamp biomicroscope Haag streit slit lamp biomicroscope
  8. 8. 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
  9. 9. Instrumentation  Operational components of slit lamp biomicroscope essentially consist of: Illumination system Observation system Mechanical system
  10. 10.  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.
  11. 11. 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.
  12. 12.  Projection lens:  Form an image of slit at eye.  Advantages,  1.keeps the aberration of lens down.  2.increase the depth of focus of slit.
  13. 13.  Reflecting mirrors and prisms  Filters Yellow barrier filter Red free filter Neutral density filter Cobalt blue filter diffuser
  14. 14. Observation system(microscope)  Observation system is essentially a compound microscope composed of two optical elements objective , eyepiece  It presents to the observer an enlarged image of a near object.  The objective lens consists of two planoconvex lenses with their convexities put together providing a composite power of +22D.  Microscope is binocular i.e. it has two eyepieces giving binocular observer a
  15. 15.  The eye piece has a lens of +10D.  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. 16. Mechanical system  Joystick arrangement  Movement of microscope and illumination system towards and away from the eye and from side and side is achieved via joystick arrangement. Up and down movement arrangement Obtained via some sort or screw devices. Patient support arrangement Vertically movable chin rest and the
  17. 17. Fixation target: A movable fixation target greatly faciliates the examination under some conditions. Mechanical coupling : Provides a coupling of microscope and the illumination system along a common axis of rotation that coincides their focal planes.  This ensures that light falls on the point where the microscope is focused  Has advantages when using the slit lamp for routine examination of anterior
  18. 18.  Magnification control : Including two or pair of readily changeable objective lenses and two sets of eyepieces.  An on and off switch and illumination control .
  19. 19. Topcon slit lamp model SL-3E Light beam is controlled by knobs Joy stick arrangement Chin rest Reflecting mirror biomicroscope Illumination control
  20. 20. Magnification may be changed by flipping a lever... Changing filters. biomicroscope Patient positioning Alignmen t mark Microscope and light source rotate indepedently
  21. 21. Filters used in slit lamp biomicroscopy  Cobalt blue filter  Used in conjunction with fluorescein stain  Dye pods in area where the corneal epithelium is broken or absent.  The dye absorbs blue light and emits green.  Uses:  Ocular staining  RGP lenses fitting  Tear layer
  22. 22.  Red free(green)filter: Obscure any thing that is red hence the red free light , thus blood vessels or haemorrhages appears black. This increases contrast ,revealing the path and pattern of inflammed blood vessels. Fleischer ring can also be viewed satisfactorily with the red green filter.
  23. 23. Illumination techniques  Includes  Diffuse illumination  Direct illumination  Parallilepiped  Optic section  Conical(pinpoint)  Tangential  Specular reflection  Indirect illumination  Retro-illumination  Sclerotic scatter  Transillumination  Proximal illumination
  24. 24. 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.
  25. 25. 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.
  26. 26. Optics of diffuse illumination Diffuse illumination with slit beam and background illumination
  27. 27. Direct illumination  Involves placing the light source at an angle of about 40-50 degree from microscope.  This arrangement permits both light beam and microscope to be sharply focused on the ocular tissue being observed.  Wide beam direct illumination is commonly used as a preliminary technique to evaluate large area.
  28. 28.  it is particularly suitable for assessment of cataracts,scars,nerves,vessels etc.  It is also of great importance for the determination of stabilization of axis of toric contact lens.
  29. 29.  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.
  30. 30. 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.
  31. 31. 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.
  32. 32.  Focusing: Beam is focused between cornea and anterior lens surface and dark zone between cornea and anterior lens observed. Principle is same as that of beam of sun light streaming through a room ,illuminating airborne dust particles. This occurance is called tyndall phenomenon.  Most useful when examining the
  33. 33. Tyndall phenomenon  Cells, pigment or proteins in the aqueous humour reflect the light like a faint fog.  To visualise this the slit illuminator is adjusted to the smallest circular beam and is projected through the anterior chamber from a 42° to 90° angle.  The strongest reflection is possible at 90°.
  34. 34. Optic section  Optic section is a very thin parallelepiped and optically cuts a very thin slice of the cornea.  Axes of illuminating and viewing path intersect in the area of anterior eye media to be examined e.g. the individual corneal layers.  Angle between illuminating and viewing path is 45 degree.  Slit length should be kept small to minimize dazzling the patient.
  35. 35.  With narrow slit the depth and portion of different objects(penetration depth of foreign bodies, shape of lens etc) can be resolved more easily.  With wider slit their extension and shape are visible more clearly.  Magnification: maximum.  Examination of AC depth is performed by wider slit width .1-.3mm .
  36. 36.  Used to localize: Nerve fibers Blood vessels Infiltrates Cataracts AC depth.
  37. 37. 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.
  38. 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. 39.  Observe: Anterior and posterior cornea Iris is best viewed without dilation by this method. Anterior lens (especially useful for viewing pseudoexfolation).
  40. 40. Example of tangential illumination (iris).
  41. 41. 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.
  42. 42.  Irregularities ,deposits ,or excavasation in these smooth surface will fail to reflect light and these appears darker than surrounding.  Under specular reflection anterior corneal surface appears as white uniform surface and corneal endothelium takes on a mosaic pattern.  Used to observe:  Evaluate general appearance of corneal endothelium  Lens surfaces  Corneal epithelium
  43. 43. Schematic of specularreflection. Reflection from front surface endothelium
  44. 44. Indirect illumination  The beam is focused in an area adjacent to ocular tissue to be observed.  Main application:  Examination of objects in direct vicinity of corneal areas of reduced transparency e,g, infiltrates,corneal scars,deposits,epithelial and stromal defects  Illumination:  Narrow to medium slit beam  Decentred beam  Magnification: approx. m=12x (depending upon object size)
  45. 45. Retroillumination  Formed by reflecting light of slit beam from a structure more posterior than the structure under observation.  A vertical slit beam 1-4mm wide can be used.  Purpose: Place object of regard against a bright background allowing object to appear dark or black.
  46. 46.  Used most often in searching for keratic precipitates and other debris on corneal endothelium.  The crystalline lens can also be retroilluminated for viewing of water clefts and vacuoles of anterior lens and posterior subcapsular cataract
  47. 47.  Direct retroillumination from iris: Used to view corneal pathology. A moderately wide slit beam is aimed towards the iris directly behind the corneal anomaly. Use magnification of 16x to 25x and direct the light from 45 degree. Microscope is directed straight ahead .
  48. 48. Schematic of direct retroillumination from the iris. direct retroillumination from the iris.
  49. 49.  Indirect retroillumination from iris: Performed as with direct retroillumination but the beam is directed to an area of the iris bordering the portion of iris behind pathology. It provides dark background allowing corneal opacities to be viewed with more contrast. Observe: Cornea, angles.
  50. 50. Retroillumination from fundus(red reflex photography)  The slit illuminator is positioned in an almost coaxial position with the biomicroscope.  A wide slit beam is decentered and adjusted to a half circle by using the slit width and  The decentred slit beam is projected near the pupil margin through a dilated pupil.
  51. 51. Schematic of retroillumination from the retina. Example of retroillumination from the reti
  52. 52. Sclerotic scatter  It is formed by focusing a bright but narrow slit beam on the limbus and using microscope on low magnification.  Such an illumination technique causes cornea to take on total internal reflection.  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.
  53. 53.  Used to observe: Central corneal epithelial edema Corneal abrasions Corneal nebulae and maculae.
  54. 54. Schematic of sclerotic scatter. Example of sclerotic scatter.
  55. 55. Proximal illumination  This illumination technique is used to observe internal detail, depth, and density.  Use a short,fairly narrow slit beam.  Place the beam at the border of the structure or pathology.  The light will be scattered into the surrounding tissue, creating a light background that highlights the edges of
  56. 56.  Depending on the density of the abnormality, the light from behind may reflect through, allowing detailed examination of the internal structure of the pathology.  Observe: corneal opacities (edema, infiltrates, vessels, foreign bodies), lens, iris
  57. 57. Transillumination  In transillumination, a structure (in the eye, the iris) is evaluated by how light passes through it.  Iris transillumination:  This technique also takes advantage of the red reflex.  The pupil must be at mid mydriasis (3to 4 mm when light stimulated).  Place the light source coaxial (directly in line) with the microscope.
  58. 58.  Use a full circle beam of light equal to the size of the pupil.  Project the light through the pupil and into the eye .  Focus the microscope on the iris.  Magnification of 10X to 16X is adequate  Normally the iris pigment absorbs the light, but pigmentation defects let the red fundus light pass through..  Observe: iris defects (they will glow with the orange light reflected from the fundus)
  59. 59. Basic slit lamp examination  Patient positioning: Head support unit Adjust height of table or chair Adjust height of chin rest such that patients lateral canthus is aligned with the mark. Adjust ocular eyepieces.
  60. 60. Power up Fixation Magnification : begin with 6x -10x magnification Focusing Special procedures Protocol and documentation
  61. 61. Uses of slit lamp biomicroscopy  Diagnostic: OCT FFA Anterior segment and posterior segment diseases Dry eye
  62. 62.  Procedures:  Applanation  Tear evaluation  Pachymetry  Gonioscopy  Contact lens fitting  Therapeutic:  Laser  FB removal  epilation
  63. 63. Anterior and posterior segment disease evaluation  Lids and lashes  Conjunctiva and cornea  Instillation of fluorescein and BUT measurement  Eversion of the lids  Anterior chamber and angle measurement  Iris  Crystalline lens  Anterior vitreous
  64. 64. Injected conjunctivaMeibomian gland openings pinquecula, INSTILLATION OF FLUORESCEIN PALPEBRAL CONJUNCTIVA EXAMINATION
  65. 65. Evertion of lids  This technique is used to examine the inferior and superior palpebral conjunctiva, particularly in contact lens wear and when looking for allergic conjunctival changes, papillae, and foreign bodies.  1. Ask the patient to look down and grasp the superior eyelashes.
  66. 66.  2. Press gently on the superior margin of the tarsal plate using a cotton swab (or the index finger of the other hand), and at the same time pull the eyelashes upwards.  3. To evert the lower eyelid, pull the eyelid down and press under the eyelid margin while moving finger upwards. The eyelid will evert over finger.
  67. 67. Meibomian gland evaluation  With the patient at the biomicroscope, use white light and medium magnification to inspect the lower eyelid margins.  Look for capping of the meibomian gland orifices (yellow mounds), notching of the eyelid margins (indentations) and frothing of the tears on the eyelid margins.  Pull the lower eyelid down and look for concretions in the palpebral conjunctiva.
  68. 68.  With mild pressure, press on the eyelid margins near the eyelashes and watch the meibomian gland orifices.  Clear fluid should be expressed.  Capping of the orifices, a cheesy secretion on expression and frothing of the eyelid margins indicates meibomian gland dysfunction.
  69. 69. CENTRAL RETINA PHOTOGRAPHS WITH A 90-DIOPTER LENS  A moderate slit beam in the almost coaxial position gives the best results.
  70. 70. References  Clinical procedure in optometry  Primary care optometry  Borishs clinical refraction  Theory and practice of optics and refraction:AK Khurana  internet