History and parts of slit lamp examination

History and parts of slit lamp examination

1. SLIT LAMP EXAMINATION- History and parts DR P DILIP FIRST YEAR POST GRADUATE

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. 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. 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. Large Gullstrand Ophthalmomicroscope (1911)

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. Zeiss slit lamp biomicroscope Haag streit slit lamp biomicroscope

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

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. 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. 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. Reflecting mirrors and prisms Filters Yellow barrier filter Red free filter Neutral density filter Cobalt blue filter diffuser

14. Observation system(microscope) Observation system is essentially a compound microscope 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 with their convexities put together 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 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 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 provision to adjust height of table.

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 segment of eye.

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

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

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. 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. Thank You