SLIT LAMP EXAMINATION.pptx slit lamp exam

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1. SLIT LAMP EXAMINATION

2. Is a unique instrument that permits magnified examination of transparent and translucent tissues of the eye in cross- section. It enhances the external examination by allowing a binocular, stereoscopic view with a wide magnification ×10-×500 Permits applanation tonometry to measure IOPs and examination of posterior segment

3. Uses of slit lamp Provides detailed examination of virtually all tissues of the eye and its adnexia Routinely used for examination of the anterior segment, vitreous and structures anterior to it. Optical constraints of the instrument and eye to be examined prevent useful visualization of the angle of the AC and other structures posterior to A/ viterous . Used in tonometry Linear measurement of tissues or lesions Ophthalmic photography Contact lens fitting

4. Parts of a slit lamp

5. The slit lamp has three principal portion: Viewing arm containing eye piece and magnifying elements Illumination arm: light source and many of controls Patients position frame

6. 1 eye piece 2 viewing arms 3 instrument magnification elements 4 a lever for adjusting magnification 5 illumination arm 6 illumination lamp 7 calibrated scale 8 lever adjusting brightness of the light beam; different light ;blue, green, red light

7. 9 a projecting knurled knob 10 knob facing examiner 11 Knurled dual knobs for changing the width of the beam light 12 patients positioning frame 13 two upright metal rods to which are attached the forehead strap 14 patients chin rest 15 a pad of disposable paper are attached 16 fixation light 17 Joy stick

8. Illumination Magnification Joystick assembly Pt- rest assembly

9. Magnification Eye piece Objective piece

10. Forehead strap Chin Rest

11. Joy stick assembly

12. Stand

13. Preparing and positioning a patient The patient’s head is positioned and steadied for the examination by means of a chin rest and forehead strap Chin rest has a concave plastic cup to which is attached a stack of disposable tissue papers The height of the patient is lowered or raised by means of a nearby knob The patient’s eye is brought level with the black demarcation line, one of the support’s rods.

14. cont The patient’s chin should be well seated in the chin rest The forehead pressed firmly against the forehead strap Patient may drift backwards and so they need help The viewing and illumination parts should be in good condition It can be difficult to position the slit lamp and its head rest close to obese patients; their upper body tend to push everything away

15. cont Patients who are relatively short can be supported by sitting on a pillow Children are examined either by standing or kneeling on the chair Ask the patient if they are comfortable before you start examination

16. Height

17. Distance

18. Principles of slit lamp special properties Direct illumination Direct focal illumination Specular reflection Trans illumination or retro illumination Indirect lateral illumination Sclerotic scatter

19. Diffuse illumination Is used mainly in obtaining an overview of ocular tissues e.g. conjunctiva Can be used to examine intraocular tissues like iris, and lens capsule May be used by red light cobalt light With white light use full height broad beam directed on the surface of the eye. The brightness can be lowered since the broad beam will be uncomfortable for the patient .

20. cont The cobalt blue produces green yellow color with fluorescein This is used to evaluate ulcers discern fluorescein pattern during Goldman Applanation

21. Direct focal illumination Is achieved by directing a full height, medium width, medium bright beam obliquely into the eye, focusing on the cornea a quadrilateral block of light illuminates the cornea The anterior surface of the paralleled piped represents the anterior surface of the cornea The posterior surface represents the posterior surface of the cornea The same can be applied to focus on the crystalline lens When the light is shortened its used to grade flare and

22. Cell in the anterior chamber.

23. Specular reflection Also reflected illumination Used to examine corneal endothelium May also be used to focus the lens and corneal surface When reflected on the cornea the examiner can identify single cells of endothelium Medium to narrow beam is applied to examined the surface of the eye A bright zone of this reflection will be evident on the temporal and mid periphery of corneal epithelium

24. Transillumination Also known as retroillumination , backlights tissues to be examined Allows to examine vacuoles edema in the corneal endothelium, blood vessels in the cornea, atrophy of the iris and other abnormalities on the cornea Transillumination of the fundus is well appreciated in a dilated pupil.

25. Indirect lateral illumination The light is directed just to the side of the lesion to be examined Some of the light enters the lesion causing it to glow internally Most useful for translucent lesion like corneal opacity or iris nodules

26. Scleratic scatter Is usefull in detecting subtle corneal opacities The less transparent areas become highlighted as they scatter the internally reflected light It requires making the illumination arm not parfocal with the viewing arm Is directed on the limbus by rotating the illuminating arm temporary while the examiner views the center of the cornea. The light from the limbus traverses the cornea by alternately reflecting off the anterior and posterior corneal surface

27. Goldman tonometry Tonometry is the objective measurement of intraocular pressure , based most commonly on the force required to flatten the cornea or the degree of corneal indentation produced by a fixed force

28. Technique The patient is positioned at the slit-lamp with the forehead firmly against the headrest. Topical aneasthesia and fluorescein are instlled into the conjunctival sac With the cobalt blue filter and the brightest beam projected obliquely at the prism, the prism is centred in front of the apex of the cornea The dial is preset between 1 and two The prism is advanced until it just touches the apex

29. Of the cornea Viewing is switched to the ocular of the slit-lamp A pattern of two semi-circles will be seen one above and one below the horizontal midline which represent the fluorescein stained tear film touching the upper and lower outer halves of the prism The dial on the tonometer is rotated to align the inner margins of the semicircles just touching The reading on the dial multiplied by ten=IOPs

30. Potential errors Inappropriate fluorescein pattern- resulting from excessive fluorescein Pressure on the globe- patient squeezing the eye Corneal edema Corneal thickness- thin cornea lead to underestimation Incorrect caliberation

31. Reducing risk of infection Avoid tonometry in individuals with overt infection Using a disposable sleeves which covers the tip of tonometer Swabbing the tip of tonometer thoroughly with alcohol prep pads Wiping and the soaking the tonometer in 3% solution of hydrogen peroxide

32. Schiozt tonometer

33. procedure

34. Gonioscopy This involves the examination and analysis of the angle Diagnostic - facilitates the identification of abnormal angle structures and estimation of the width of the chamber angle Surgical - involves visualization of the angle during procedures like goniotomy

35. Technique The preliminary steps are the same as for fundus examination The angle is visualized with the small dome shaped gonioscopic mirror Initially the mirror is placed at 12o’clock to visualize the inferior angle When the view of the angle is obscured by a convex iris, it is possible to see over the hill by asking the patient to look in the direction of the mirror.

36. When the plane of the iris is flat the patient should be asked to look away from the mirror in order to obtain a view parallel to the iris with optimal image quality

37. Identification of angle structures Schwalbe line The corneal wedge Trabeculum meshwork Schlemm canal Scleral spur The ciliary body Iris process Blood vessels

38. Grading Grade 4 (35-45 ⁰) is the widest angle characteristic of myopia in which the ciliary body can be visualized with ease, it is capable of closure Grade 3(25-35 ⁰) is an open angle in which at least the scleral spur can be identified, it is also incapable of closure Grade 2(20⁰) is a moderate narrow angle in which only trabeculum can be identified; angle closure is possible but unlikely

39. Grade 1(10⁰) is very narrow angle in which only schwalbe line, and probably the top of trabeculum can be identified Slit angle is one there is no obvious iridocorneal contact but no angle contact but no angle structures can be identified. The angle has greatest danger of eminent closure Grade 0 is closed due to iridocorneal contact

40. Gonioscopy

41. Goniolenses Goldmann Single or triple mirror Zeiss Contact surface diameter 12 mm Coupling substance required Four mirror Coupling substance not required Contact surface diameter 9 mm Suitable for ALT Not suitable for indentation gonioscopy Suitable for indentation gonioscopy Not suitable for ALT

42. Tonometers Goldmann Contact applanation Perkins Portable contact applanation Pulsair 2000 (Keeler) Air-puff Schiotz Portable non-contact applanation Non-contact indentation Contact indentation Tono-Pen portable contact applanation