This document describes various illumination techniques used with a slit lamp to examine different parts of the eye. It discusses diffuse, direct, tangential, and specular illumination techniques as well as indirect, retroillumination, and Van Herrick techniques. Each technique is used to illuminate a specific area of the eye in order to observe different structures like the cornea, iris, lens, anterior chamber angle, and detect any pathologies present. Proper illumination angles and magnifications are outlined for visualizing various eye tissues and evaluating properties like surface texture and integrity.

1. Slit Lamp Illumination Techniques Author: Irina Jagiloviča e-mail: [email_address] www: www.optometristiem.lv

2. Diffuse Illumination Light is spread evenly over the entire observed surface The beam is opened all the way. Direct the light onto the eye at a 45 degree angle The microscope is directed straight ahead. Observe: eyelids, lashes, conjunctiva, sclera, pattern of redness, iris, pupil, gross pathology, and media opacities

3. Diffuse Illumination

4. Diffuse Illumination

5. Direct Illumination Techniques Beam The microscope is usually directed straight ahead but may also be moved to an angle opposite the illuminator. The greater the angle between the illuminator and the microscope, the greater the width of the illuminated section. A very narrow beam (optical section) directed onto the cornea can be used to evaluate corneal shape, elevation, and thickness. Observe: cornea, iris, lens, vitreous

6. Beam

7. Beam

8. Tangential Illumination This technique is used to observe surface texture. Medium-wide beam of moderate height Swing the slit lamp arm to the side at an oblique angle Magnifications of 10X, 16X, or 25X are used Observe: anterior and posterior cornea, iris, anterior lens (especially useful for viewing pseudoexfoliation)

9. Tangential Illumination

10. Specular Reflection Specular reflection is used to visualize the integrity of the corneal and lens surfaces. If the surface is smooth, the reflection will be smooth and regular; if the surface is broken or rough Position the illuminator about 30 degrees to one side and the microscope 30 degrees to the other side To visualize the endothelium, start with lower magnification (10X to 16X). Direct a relatively narrow beam onto the cornea Switch to the highest magnification available. Endothelium is best viewed using only one ocular, so you may want to close one eye. Observe: corneal epithelium and endothelium, endothelial mosaic, lens surfaces

11. Specular Reflection

12. Specular Reflection

13. Indirect Illumination Proximal Use a short, fairly narrow slit beam. Place the beam at the border of the structure or pathology Observe: corneal opacities (infiltrates, vessels, foreign bodies)

14. Proximal

15. Sclerotic Scatter A tall, wide beam is directed onto the limbal area. When the light is properly aligned with regard to the eye, a ring of light will appear around the cornea. The light is absorbed and scattered through the cornea highlighting pathology. Use 10X magnification, with the microscope directed straight ahead Observe: general pattern of corneal opacities

16. Sclerotic Scatter

17. Sclerotic Scatter

18. Sclerotic Scatter

19. Retroillumination Retroillumination is used to evaluate the optical qualities of a structure. The light strikes the object of interest from a point behind the object and is then reflected back to the observer

20. Retroillumination

21. Indirect Retroillumination from the Iris the beam is directed to an area of the iris bordering the portion of the iris behind the pathology This provides a dark background, allowing corneal opacities to be viewed with more contrast

22. Retroillumination from the Fundus (Red Reflex) The slit beam at 2 to 4 degrees Shorten the beam to the height of the pupil to avoid reflecting the bright light off of the iris. Focus the microscope directly on the pathology using 10X to 16X magnification. Opacities will appear in silhouette. This view is best accomplished if the pupil is dilated.

23. Retroillumination From the Fundus (Red Reflex)

24. Van Herrick Technique Use to evaluate anterior chamber angle without gonioscopy Medium magnification Angle 60 degrees Narrow beam close to limbus Depth of anterior chamber is evaluated it to the thickness of cornea: 4. grade – open anterior chamber angle 1:1 ratio 3. grade – open anterior chamber angle 1:2 ratio 2. grade – narrow anterior chamber angle1:4 ratio 1. grade – risky narrow anterior chamber angle less than 1:4 ratio 0. grade – closed anterior chamber , cornea “sits” on iris

25. Van Herrick Technique

26. Van Herrick Technique 1. grade – risky narrow anterior chamber angle less than 1:4 ratio

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