Objective 2a Direct Illumination Flashcards
What is the use of Diffuse Illumination (Broad beam)?
Provides a general survey of the external surfaces of the eye.
How do you preform Diffuse illumination?
Illumination: Wide beam is directed obliquely to the area of interest.
Rheostat: lowest setting.
Microscope: low magnification focused at the area of interest.
What is Parallelepiped Illumination used for?
Used to make a general yet more specific survey of the cornea and conjunctiva. Gives a broad view of the anterior and posterior corneal surfaces. Useful for detection of corneal staining, foreign bodies, opacities, and observing tear film.
How is Parallelepiped Illumination preformed?
Illumination: Moderate slit set at a 45 deg angle to the microscope
Microscope: Moderate magnification is focused sharply on the cornea. A wide block view of illuminated cornea should be in view.
What is Narrow Slit Illumination used for? (Optical Sectioning)
To descover thickening, thinning, and distortions in the cornea or lens. Estimate depth of foreign bodies or opacities in the cornea or lens. Examine contact lens/ corena relationship. Estimate anterior chamber depth.
How is Narrow slit illumination preforemed?
Illumination: The narrowest beam possible focused on the cornea or lens. Set at 45-60 deg angle to the microscope for a better view.
Microscope: Moderate to high magnification.
What is Tangential Illumination used for?
Give an enhanced view of the surface texture of the iris (ex iris lesions). Creates highlights and shadows giving dimension to otherwise smooth appearing surfaces. Effective in determining raised areas on the iris as in tumors and used as an adjunt technique in determining glaucoma.
How is Tangential Illumination preformed?
Illumination: Moderate to wide beam directed from a sharply oblique tangential angle to the limbal area.
Microscope: low to moderate magnification focused at the level of the light beam.
What is Conical Beam Illumination used for?
Detection of Inflammation in the eye known as cells and flare.
How is Conical Beam Illumination preformed?
Illumination: the smallest circle beam of light is set at 45deg angle to the microscope and directed through the cornea into the anterior chamber. Focus at an area between the iris and the cornea.
Microscope: High magnification
What are Cells and Flare?
Cells are blood cells (have the appearance of particles of dust in a sunbeam.)
Flare is increased protein in the anterior chamber (appears as a clear headlight cutting through a foggy night.)
What is Specular Reflection used for?
Used in studying the corneal epithelium, endothelium and the lens. Assessment of the integrity of tear film, epithelium , endothelium and lens surfaces by creating a mirror-like reflection from the surface. It is the ONLY illumination the allows for assessment of the endothelium.
How is Specular Reflection preformed?
Illumination: Moderate slit beam
Microscope: High magnification. Should be viewed at angle opposite that of illumination. (incident=reflection) 30 deg to either side of the px’s visual axis with slit beam on the temporal side and scope nasally.
Image is only visible in one ocular at a time.
