Objective 2c Retroilluminaton Flashcards
What is retro-illumination ?
Light is deliberately focused on and bounced off a structure, such as the anterior part of the iris or the retina. With this illumination corneal anomalies that would be difficult to see by other techniques become visible.
What is Direct Retro-illumination from the iris used for?
Helpful in studying corneal abnormalities which are difficult to visualize by direct focal illumination. Subtle abnormalities or corneal changes become more apparent when visualized against a light background.
How is Direct Retro-illumination preformed?
Illumination: Moderate slit beam directed onto the iris surface behind the pathology.
Microscope: observe the image directly in front of the reflected light
Why is the use of the word “direct” in Direct Retro-illumination of the iris confusing?
Direct retro-illumination from the iris is an actual form of INDIRECT illumination. the beam should be placed on an area of the iris that is in line with the particular corneal defect you wish to highlight and the cornea is indirectly illuminated.
What is Retro-illumination from the iris used for?
Helpful in viewing subtle corneal changes which become more apparent when visualized in the interface between the light and dark areas created by the light beam. These changes may interfere with achieving normal acuity such as cataracts.
How is Retro-illumination from the iris preformed?
Illumination: moderate slit beam directed onto the surface behind and adjacent to the pathology
Microscope: Observe the image adjacent to the reflected light.
What is Iris Transillumination used for?
To view iris defects or abnormalities, such as iris atrophy. Done on undilated pupil allowing the examiner to view defects in the pigmented layer of the iris.
How is Iris Transillumination preformed?
Illumination: a full circle beam of light is projected through the pupil. The slit illuminator is put in a coaxial position with the microscope
Microscope: moderate magnification. Defects in the iris will be visible by transmitting the orange/ red light reflected from the fundus.
