3. THE SLIT-LAMP BIOMICROSCOPE is a high-power binocular microscope with a slit-shaped illumination source, specially designed for viewing the different optically transparent or translucent tissues of the eye.
It enhances the examination by :
Excellent image quality
Binocular stereoscopic view
Flexible illumination
Flexible magnification
Providing room for specialized attachments and lenses for detailed examination and diagnostic tests
4. The science of examination with a slit lamp is called Biomicroscopy as it allows in vivo study of living tissues at high magnification.
Cont…
6. •1911, the first concept of slit-lamp was introduced by ALLVAR GULLSTRAND, it was named as “Large reflection-free ophthalmoscope” manufactured by Zeiss.
Prof. Allvar Gullstrand
Large Gullstrand Opthalmoscope (1911)
7. •1919, VOGT introduced KOEHLER illumination system to Gullstrand slit-lamp.
•1930, LETZ introduced telescopic loupe built on the principle of Galilean Telescope which helps in increase working distance. Haag-Streit-1920
Bausch & Lomb slit lamp (1926)
Cont…
8. •1933, GOLDANN developed three control element for cross-slide stage and also common swivel axis for microscope and illumination system in HAAG-STREIT Slit-lamp.
•1938, Joystick was added to Haag-streit. Haag-Streit-1933
Haag-Streit-1936
Cont…
9. •1950, LITTMANN with ZIESS combined joystick control from Goldmann, illumination path from Comberg prism instrument and also added stereo telescope system with magnification changer.
Cont…
Zeiss slit lamp (Littmann) (1950)
Haag-Streit-1959
10. Fig. : Modern slit-lamp Cont…
•Onward modern slit-lamp system began to come into light.
18. Illumination system Principle :
Kohler illumination principle is used in both Zeiss & Haag-streit type illumination system.
The light filament (F) is imaged on to the objective lens (O) but the mechanical slit (MS) is imaged on to the patient’s eye (S)
19. Microscope system Principle :
The eyepiece (Ocular) uses Astronomical telescope system.
Here two convex lenses used one in front of other separated by the distance of their focal length. Fig. : Slit-lamp biomicroscope optical principles
20. A Galilean telescope system is used for even higher and changeable magnification.
Here a convex and a concave lens is used in line separated by the distance of their focal length.
Cont…
Fig. : Slit-lamp biomicroscope optical principles
21. Both telescope systems produce inverse image of an object so an inverting prism named Porro- Abbe prism is used to produce right way erect image.
Here two triangular prisms use the total internal reflection principle of optics.
Cont… Porro-Abbe Prism
Fig. : Slit-lamp biomicroscope optical principles
22. The telescope system provide considerable distance between the microscope and the patient’s eye, so that certain maneuver like foreign body removal from the cornea or using extra lenses for fundus examination can be done.
Cont…
23. Parfocality : The point at which the microscope is focused corresponds to the point on which the light is focused, this coupling effect is called parfocality.
This is achieved by the microscope and the illumination system, having a common focal plane and their common axis of rotation also lies in that focal plane.
Cont…
25. Basic Design :
1.Mechanical system
2.Illumination system
3.Biomicroscope /Observation system
Associated instruments :
•Applanation Tonometer
•Gonioscopic Lens
•Fundoscopy Lens
•Micrometer Eyepieces
•Image archiving device
•Laser delivery system
26. It concern with :
•Positioning & adjustment of patient and observer
•Maneuvering the illumination and microscope system together with joystick
•Providing base to other parts
Mechanical system :
Basic 3 parts :
1.Motorized table (Base)
2.Patient positioning frame
3.Joystick
27. Parts of mechanical system :
Cont… Fixation target Chin rest adjustment knob
Joystick Power switch Table height adjustment Forehead band
Canthus alignment
Chin rest Hand grip for patient Lock for slit lamp base
Low friction plate
28. Provides a bright, evenly illuminated, finely focused, adjustable slit of light at the eye.
Contains the following components:
•Light source
•Condenser lens system
•Slit and other diaphragms
•Filters
•Projection lens
•Reflecting mirror or prisms
Illumination system :
29. Parts of illumination system :
Cont…
Scale for slit height
Slit height control Inclined mirror Latch to tilt light column Light source Filter control
Centering screw Slit width control
30. •Essentially these are compound microscopes composed of optical elements providing enlarged right way stereoscopic image to observer.
•Provides larger working distance in front of microscope for manipulation on patient’s eye.
•Magnification changer for detail view.
Observation system :
31. Parts of observation system :
Cont… Eyepiece
Marked ring for
Adjustment of examiner’s
refractive error Prism housing Knob to change magnification Objective lens
34. Prerequisites :
•Switch on power & unlock base screw
•Cleaning the forehead band
•Changing paper strip from chinrest
•Comfortable sitting of pt. and the examiner
•Counseling the patient
•Proper positioning of the pt.
•Target fixation
•Adjust eyepieces to correct for examiner’s refractive error and interpupillary distance
•Children may need to stand, or they can sit on parent’s lap or kneel on a stable chair
Fig. Correct positioning at the slit lamp.
35. Chronology for slit-lamp examination : Eyelids
Eyelid margins Tear film Conjunctiva Cornea
Aqueous humor
Iris Lens Vitreous (ant.)
36. Illumination techniques :
Slit Width control knob:
Narrow to fully open slit illumination achieved by rotating this knob
37. Illumination techniques :
Slit height control knob :
Short to long slit illumination achieved by rotating this knob
Cont…
39. Illumination techniques :
Tilting light column :
Illumination column can be tilted 5-20°, with vertical axis which gives extra plane and minimize reflection during posterior segment examination with condensing lens.
Cont…
41. Direct diffused illumination :
•illumination of the eye with a broad, unfocused light beam
•directed obliquely between 30-450
•magnification 6x to 10x
Application :
•General gross overview of eyelids, lashes, conjunctiva, sclera, pattern of redness, iris, pupil, gross pathology, ant capsule of lens
Cont…
43. Direct focal illumination :
•Illumination and observation are focused in the same plane
•slit width narrow to broad
•Illumination angle 45° to 60°
•Magnification 10x-40x
Application :
•Cornea in detail
•Anterior chamber
•Crystalline lens
•Anterior part of vitreous
•Grading cell and flare in anterior chamber
Cont…
45. Direct focal illumination :
i.Parallelepiped
•Slit width 2-4 mm obliquely focusing on the cornea so that a quadrilateral block of light illuminate the cornea
Application :
•To examine corneal surface, stroma
•To ascertain depth (FB, abration)
Cont…
46. Direct focal illumination :
ii.Optical section
•Slit width 1mm or less
•Illumination angle 45-60° or more
•High illumination & magnification
Application:
•Corneal depth, layers, scars, vessels
•Lens opacity
Cont… 1. Tear film 2. Epithelium 3. Ant. Stroma 4. Post. Stroma 5. Descemet’s mem. & Endothelium
47. Direct focal illumination :
iii.Conical beam
•Assessment of particles floating in the A/C
•Narrow, short & bright slit of light
•45°-60° light source directed to pupil
•Magnification 16x-25x
Application :
•Inflammatory cells, flare, pigmented cells, metabolic wastes
Principle : Tyndall phenomenon
Cont…
48. Specular reflection :
•Angle of incidence = angle of reflection
•Observation and illumination system have same angle with perpendicular axis to each other
•Slit width < 4mm
•The light reflected from the anterior or posterior corneal surface
•Best view with one eye
Application :
•assessment of surfaces
Corneal epithelium
Corneal endothelium
Lens surface
•assessment of tear film
Cont…
Corneal endothelium
49. Tangential illumination :
•A narrow light beam is projected almost parallel along the structure to be observed
•Elevated structures are visible by shadowing
•Illumination angle 90°
•Magnification 10-25x
Application :
•elevated abnormities or changes in the iris
•tumors, cysts
Cont…
50. Indirect illumination :
•The beam is focused in an area adjacent to ocular tissue to be observed
•Decentered beam
•Illumination 2 to 4mm slit
•Magnification: Low to medium (depending upon object size)
Application:
•infiltrates
•corneal scars
•deposits
•epithelial and stromal defects
Cont…
52. Retro-illumination :
•Light reflected on iris or fundus
•Microscope focused on cornea
•Two types: direct and indirect
Application :
For better visualization of
•Epithelial cysts
•Keratic precipitates
•Small blood vessels
•Small scar
Cont…
53. Direct retro-illumination :
•Observed feature is viewed in direct pathway of reflected light
•with this illumination findings are made visible with high contrast
•medium slit width 2 to 4mm
•Illumination angle 45-60°
Application :
•Infiltrations, small scars, corneal vessels, etc.
Cont…
54. Indirect retro-illumination :
•Observer at right angle to the observed structures
•Illumination angle greatly reduced or increased
•Feature on the cornea is viewed against a dark background
•medium slit width 2 to 4mm
Application :
•Infiltrations, small scars, corneal vessels, micro cysts, vacuoles
Cont…
56. •This technique is used to observe media clarities and opacities.
•The pupil is dilated
•the slit beam and microscope are made co-axial and light strikes the fundus and creates a glow behind the opacity in the media
•The media opacity creates a shadow in the glow
Applications
•abnormities in the anterior vitreous, lens, anterior chamber, cornea
Cont…
Retro-Illumination from the Fundus :
57. Sclerotic scatter :
•Light incident on the limbus with 2-4mm slit at an angle of 45° - 60°
•Decentered slit
•The microscope focused centrally
•Total internal reflection of the incoming light at inner corneal boundaries (endothelium and epithelium)
Applications
•scars, foreign bodies, corneal defects
•irregularities in the cornea
Cont… Fig. : Corneal scar
58. Iris-transillumination :
•Transillumination of the iris by indirect light reflected from the fundus
•Mid dilated pupil (3 to 4mm)
•Illumination and observation at coaxial position
Applications
•Visualization of defects of the pigment layer of the iris
Cont…
Fig. : Transillumination in Albinism
59. Oscillatory illumination :
•Moves the beam (usually an optical section) from nasal to temporal limbus
•Viewed alternately by direct and indirect illumination
•Often possible to see minute objects or filaments, specially in the aqueous
•Reveals subtle areas of corneal thinning.
Cont…
60. Van Herrick’s Technique :
•Used to evaluate anterior chamber angle without gonioscopy
•Narrow slit beam close to limbus with Illumination angle 60°
•Medium magnification
Principle :
•Compare the width of cornea seen by optical section with the dark section seen between ant. surface of iris & back of cornea
Interpretation :
Grade 4 – open anterior chamber angle 1:1 ratio
Grade 3 – open anterior chamber angle 1:2 ratio
Grade 2– narrow anterior chamber angle1:4 ratio
Grade 1– risky narrow anterior chamber angle less than 1:4 ratio
Grade 0– closed anterior chamber
63. Applanation Tonometer :
The Goldmann Applanation Tonometer is the most common tonometer that usually mounted on the standard slit- lamp biomicroscope.
It’s easy to use and measure the IOP of a seated patient with high accuracy in most clinical situations.
Parts :
1.Tonometer tip (biprism)
2.Metal rod
3.Tonometer housing
4.Force adjustment knob
Associated instruments :
64. Principle :
•Applanated force (AF) equals the intraocular pressure (IOP)
•diameter of the applanated area: 3.06 mm here counteracting forces of corneal rigidity and capillary attraction cancel each other
Application :
•Measurement of intraocular pressure (IOP)
Cont…
65. Procedure :
1.Proper positioning of the patient
2.Instill topical anesthetic and flurescein in pt.‘s eye
3.Place the cobalt blue filter with broad slit illumination at 60-90° angle
4.The dial is preset between 1 and 2 (i.e. 10–20 mmHg)
5.Prism is advanced until it just touches the apex of the cornea
6.Viewing into the oculars a pattern of two semicircle will appear which represent the fluorescein-stained tear film touching the prism
Cont…
66. Procedure :
7.Then gently rotate the force adjustment knob of tonometer to align the inner margins of the semicircles
8.The reading on the dial, multiplied by 10, gives the IOP. Modern digital display system provides actual reading without multiplication
9.Repeat the procedure for other eye
10.At last wash B/E with antibiotic eye drop
Cont… Video clip : GAT
67. Fundus Observation and Gonioscopy :
•Different types of Contact and Non-contact lenses used for examination, diagnostic and therapeutic purpose in fundoscopy and gonioscopy
•With classic three mirror Goldmann lens post. Segment and irido corneal angle can examined simultaneously
68. Cont…
Fundoscopy :
Contact Glasses :
•Additional tool for fundus observation with the slit lamp
•Mostly direct; erect and non mirrored image of the fundus
•Required :
•dilated pupil
•use of coupling liquid (Hypromellose 0.3%)
•Coaxial angle (0°)
•Illumination – low with 2-4 mm slit
•Magnification – 10-16 x
69. Cont…
Non-contact lenses :
•Additional tool for fundus observation with the slit lamp
•Mostly indirect; upside-down and mirror image of the fundus (convex optics)
•non contact
Required:
•dilated pupil
•Coaxial angle (0°)
•Illumination - low with 2-4mm slit
•Magnification – 10-16 x
Fundoscopy :
71. Cont…
Goldmann 3-Mirror gonioscopic lens :
•Procedure same as contact fundus lens
Observation :
•Central lens (0) : Posterior pole
•73° mirror (1) : Equator
•67° mirror (2) : Ora serrata
•59° mirror (3) : Iridocorneal angle
Gonioscopy :
72. Cont…
Application :
•Grading of A/C angle width (Shaffer system)
•Peripheral anterior synechiae
•Neovascularization
•Hyperpigmentation
•Trauma
Angle recession
Trabecular dialysis
Cyclodialysis
Foreign bodies
•Blood in the Schlemm canal
Gonioscopy :
Fig.: Shaffer system grading
Fig.: Blood in chamber angle
Fig.: Neovascularization
73. •Slit-lamps have the capability of providing laser delivery with a conjunct laser system installed on it
•Lasers are used for the treatment procedures like photocoagulation, iridotomy or capsulotomy
•Commonly delivered lasers – Nd:YAG
Laser delivery system with slit-lamp : Fig.: Laser system mounted Slit-lamp
74. The slit lamp is one of the most commonly used and valuable diagnostic instruments for an ophthalmologist of today.
So user level care & maintenance is very much important to get optimum performance & long life from it.
