Slit Lamp Illuminations Flashcards
A wide beam of light is directed obliquely at the cornea with no attempt to focus the light. It provides a good over all picture of the cornea but no fine details can be seen. It is used primarily for a general survey of the eye. Uses: The extent of a corneal scar or infiltration can be observed along with the presence of folds or straie in Descemet's membrane. Corneal edema may be seen as a hazy grey, somewhat granular appearance.
Direct Focal Illumination
The microscope and the beam of light are focused on the same area. There are three types of direct focal illumination: 1) optic section, 2) parallelepiped, and 3) conical beam. Optic section is used to see all layers of the cornea. With it, is possible to determine distortions in the corneal contour and the depth of foreign bodies. Parallelepiped provides a broader view of the anterior and posterior corneal surfaces. It is used to help assess any surface irregularities which may exist and to examine the endothelium. It is often used with flourescein in helping to determine the fit of a contact lens. Conical Beam is the most sensitive method for observing flare or relucency in normal aqueous humor in the anterior chamber. Using high magnification it resembles light penetrating fog.
The observer focuses the microscope on an area immediately adjacent to the illuminated position. It is particularly valuable for studying the iris for pathology.
The light is focused on the deeper structures such as the iris, lens or retina while the microscope is focused to study the more anterior structures in the reflected light. Most typically, the light is reflected from the iris in order to study the cornea. It can be useful for the examination of corneal edema and to view blood vessels that have invaded the cornea. It can also be used to study deposits on Descemet’s membrane.
A broad beam of light is focused at the temporal limbus so it transilluminates through to the nasal limbus. The microscope is then focused sharply on the cornea. Sclerotic scatter and the unaided eye is used to detect the presence of corneal edema which appears as a foggy patch of cotton.
Cobalt Blue Filter
A cobalt blue filter is often used after the instillation of fluorescein to observe staining patterns and lens fit.
Used to decrease ultraviolet rays and minimally decrease light intensity. It is used primarily for routine examination.
Neutral Density Filter
Decreases light intensity about 10%. Used to examine eyelids and conjunctiva. Useful for photophobic patients.
Green Filter (red free)
Makes red or brown objects blacker. Useful for observing blood vessels.