wide open. Its main purpose is to illuminate as much of the eye and its adnexa at once for general observation. Direct focal illumination Observation with an optical section or direct focal illumination is the most frequently applied method. It is achieved by directing a full-height, hairline to medium width, medium-bright beam obliquely into the eye and focusing it on the cornea so that a quadrilateral block of light illuminates the transparent medias of eye. Viewing arm and illuminating arm are kept parfocal. This type of illumination is useful for depth localization. Direct focal illumination is used for grading cells and flare in anterior chamber by shortening height of beam to 2–1 mm. Specular reflection Specular reflection, or reflected illumination is just like patches of reflection seen on sunlit lake water surface. To achieve specular reflection, the examiner directs a medium to narrow beam of light (it must be thicker than an optical section) toward the eye from the temporal side. The angle of illumination should be wide (50°-60°) relative to the examiners axis of observation (which should be slightly nasal to the patients visual axis). A bright zone of specular reflection will be evident on the temporal, midperipheral corneal epithelium. It is used to see endothelial outline of cornea. Transillumination or retroillumination In certain cases, illumination by optical section does not yield sufficient information or is impossible. This is the case, for example, when larger, extensive zones or spaces of the ocular media are opaque. Then the scattered light that is not very bright normally is absorbed. A similar situation arises when areas behind the crystalline lens are to be observed. In this case the observation beam must pass a number of interfaces that may reflect and attenuate the light. Indirect illumination With this method, light enters the eye through a narrow to medium slit (2 to 4 mm) to one side of the area to be examined. The axes of illuminating and viewing path do not intersect at the point of image focus, to achieve this; the illuminating prism is decentered by rotating it about its vertical axis off the normal position. In this way, reflected, indirect light illuminates the area of the anterior chamber or cornea to be examined. The observed corneal area then lies between the incident light section through the cornea and the irradiated area of the iris. Observation is thus against a comparatively dark